Automatic tray handling system for sorter

Information

  • Patent Grant
  • 6561339
  • Patent Number
    6,561,339
  • Date Filed
    Monday, July 31, 2000
    24 years ago
  • Date Issued
    Tuesday, May 13, 2003
    21 years ago
Abstract
An automatic tray handling system for use with an article or mail sortation system, such as a flats mail sortation system, is operable to automatically remove filled or partially filled trays from individual sorter units and to replenish the sorter units with empty trays. The empty trays and/or filled trays are moved along at least one conveying surface adjacent to the sorter units. The automatic tray handling system includes a plurality of tray moving devices, which are operable to move the empty trays from the conveying surface to the sorter units, whereby the trays are at least partially filled by the sorter units. The tray moving devices are then further operable to move the at least partially filled trays from the sorter units to a conveying surface, whereby the filled trays may be conveyed to downstream operations, such as an automatic labeling station. Preferably, the empty trays are movable in a continuous loop about the mail sortation system. The automatic tray handling system may include an upper and lower conveying surface and a vertical tray moving device, which is operable to lower empty trays from the upper conveying surface to the lower, empty tray-conveying surface, whereby the empty trays are returned to an upstream end of the conveying surface along the sorter units. The empty trays may be conveyed along the conveying surfaces and may be moved into a proper position for filling at an appropriate one of the multiple sorter units positioned therealong.
Description




BACKGROUND OF THE INVENTION




The present invention relates generally to tray handling equipment for removing filled or partially filled trays from a mail sorter and replenishing the mail sorter with empty trays. The invention is particularly useful with flats mail sorters.




Flats mail sorters are known and are commercially available. Flats mail sorters sort flat mail, such as magazines, large envelopes and the like, and discharge the sorted mail into trays. Each of these trays may be devoted to a particular mail distribution center, carrier route, delivery point, zip code or the like. Typically, a mail sortation system includes one or more rows of multiple sorter units. Examples of flats mail sorters include models FSM100 and TOPS 2000, marketed in the United States by Rapistan Systems of Atecs Mannesmann AG. As the mail is sorted, the filled or partially filled trays must be removed from the location at the particular sorter and replaced with an empty tray. Occasionally, there is also a requirement that a sweep operation be performed, whereby all of the trays are removed from their respective locations, even if the trays are only partially filled. Empty trays are then stocked at each of the sorters.




The removal of filled or partially filled trays and replacement with empty trays is traditionally performed manually. One or more operators must manually remove the at least partially filled tray from each of the multiple sorters and replace it with an empty tray, such that the sorter may continue the sortation process. Accordingly, the operation of the sorting machines is quite labor intensive.




A system has been proposed which includes a shuttle cart that travels underneath the chutes of the mail sorter units and carries multiple trays thereon. The trays are hoisted up into position beneath an appropriate sorter unit and locked or clamped in position at the sorter unit, so the cart may move to another sorter unit. Once filled, the trays are grabbed and moved down onto a shuttle cart for transporting the tray from the sorter unit. Such a system requires a rigid tray that is strong enough to withstand the clamping of the tray during the filling process. The system is also slow to provide empty trays to the sorter units and to move the full trays away from the sorter units.




Therefore, it is desirable to automate the manual processes of providing an empty tray to a sorter and/or removing an at least partially filled tray from the sorter.




SUMMARY OF THE INVENTION




The present invention is intended to provide an automatic tray handling system for an article sortation system, such as a flats mail sortation system. The tray handling system is operable to remove at least partially filled trays from multiple sorter units and provide empty trays to the sorter units for filling with articles, such as mail and the like.




According to one aspect of the present invention, an automatic tray handling system for use with an article sorter includes at least one conveying surface and a plurality of tray moving devices. The article sorter includes a plurality of tray support areas for positioning a tray while the tray is being filled with sorted articles. The conveying surface is operable to convey empty trays and/or at least partially filled trays generally adjacent to the tray support areas. The tray moving devices are operable to move empty trays from the conveying surface to the tray support areas and to move at least partially filled trays from the tray support areas to the conveying surface.




In one form, the tray handling system is operable to convey empty trays in a generally continuous loop about the conveying surfaces until the empty trays are selected and filled at a sorter unit. The article sorter system may include a pair of rows of sorter units. Preferably, the conveying surfaces include a first and second conveying surface along each side of the article sorter system. Empty trays may be removed from the first conveying surface and, after filling at the sorter unit, may be inducted back onto the first conveying surface and conveyed to a labeling station at a discharge end of the tray handling system. Preferably, the first conveying surface is positioned above the second conveying surface. A vertical tray moving device may be positioned at a downstream end of the first conveying surface to remove empty trays from the first conveying surface and move the trays down onto the second conveying surface so the empty trays may continue to cycle along the conveying surfaces. A connecting conveyor may connect a downstream end of the second conveying surfaces to an upstream end of the first conveying surfaces to complete the loop.




In another form, the conveying surface comprises an empty tray conveyor and a filled tray conveyor. Empty trays are removed from the empty tray conveyor and moved to the sorter unit for filling. The filled trays or at least partially filled trays are then moved from the sorter unit to the filled tray conveyor for conveyance to a downstream operation, such as a labeling station at a discharge end of the tray handling system.




Preferably, the filled or partially filled trays are electronically identified and tracked as they proceed along the conveying surface. A labeling station may be positioned at a downstream end of the conveying surface and may be operable to create and affix a label to each filled tray as it arrives at the labeling station. The labeling station may also include a scanner to verify that the label affixed to each tray is appropriate for the electronic identification of that particular tray.




According to another aspect of the present invention, a method for handling trays is provided for use with an article sorter which includes a plurality of sorter units and a plurality of corresponding tray support areas for positioning a tray while the tray is being filled with sorted articles. The method includes providing at least one conveying surface along the sorter units and conveying empty trays along the conveying surface. The method further includes moving empty trays from the conveying surface to a tray support area and at least partially filling the empty tray at the tray support area. The partially filled trays are then moved onto the conveying surface and may then be conveyed therealong to a downstream operation, such as a labeling station.




Preferably, empty and filled trays are conveyed along a first conveying surface, while empty trays are conveyed along a second conveying surface. The empty trays may be moved from a downstream end of the first conveying surface onto an upstream end of the second conveying surface. The empty trays are than movable along the second tray conveying surface to return toward an upstream end of the first conveying surface.




In one form, the article sorter includes a pair of rows of sorter units along opposite sides of the article sorter. Preferably, the method provides for moving trays in a generally continuous loop around first and second conveying surfaces at both sides of the article sorter. More particularly, the method may provide for moving empty trays at a downstream end of the second conveying surface at a first side of the article sorter onto an upstream end of the first conveying surface at the second side of the article sorter. The empty trays are then conveyed along the first conveying surface along the second side and then moved from a downstream end thereof to an upstream end of the second conveying surface at the second side of the article sorter. The empty trays are then conveyed along the second conveying surface at the second side to a downstream end thereof. The empty trays are then moved from the downstream end of the second conveying surface at the second side to an upstream end of the first conveying surface at the first side of the article sorter. The empty trays are then conveyed along the first conveying surface at the first side of the article sorter and moved from a downstream end thereof to an upstream end of the second conveying surface at the first side. The empty trays are then conveyed along the second conveying surface at the first side to the downstream end thereof, thereby completing the continuous loop.




Preferably, the first conveying surface is positioned generally above the second conveying surface. The empty trays are moved from the downstream end of the first conveying surface to the upstream end of the second conveying surface via a vertical tray moving device. Also, the empty trays are moved from the downstream end of the second conveying surface to the upstream end of the first conveying surface via a return device, such as a connecting conveyor surface, such as an incline ramp belt conveyor.




Therefore, the present invention provides an automatic tray handling system for an article sorter which is operable to remove at least partially filled trays from a sorter unit along the article sorter and replenish the sorter unit with an empty tray. The present invention provides movement of empty trays in a generally continuous loop about the article sortation system until the empty trays are selected and filled by the sorter units. Accordingly,the present invention substantially reduces the manual labor required to exchange filled trays with empty trays at an article sortation system, such as a flats mail sorter or the like.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of an input end of an automatic tray handling system according to the present invention;





FIG. 2

is a perspective view of a discharge end of the automatic tray handling system of FIG


1


;





FIG. 3

is a top plan view of the automatic tray handling system of

FIGS. 1 and 2

, with the upper conveying surfaces partially cut away to reveal additional details;





FIG. 4

is an end elevation of the tray handling system of the present invention, taken at the input end of the tray handling system;





FIG. 5

is a partial sectional view of the tray handling system, taken along the line V—V in

FIG. 3

;





FIG. 6

is a partial sectional view of a vertical tray-moving device useful with the present invention, taken along the line VI—VI in

FIG. 3

;





FIG. 7

is a side elevation of the vertical tray-moving device of

FIG. 6

;





FIG. 8

is a top plan view of the vertical tray-moving device of

FIGS. 6 and 7

;





FIG. 9A

is a perspective view of a section of the upper conveyor and a tray moving and support apparatus useful with the present invention, with a portion of the conveyor cut away;





FIG. 9B

is an exploded perspective view of the tray moving apparatus of

FIG. 9A

;





FIG. 10

is a side elevation of a portion of the tray handling system of the present invention;





FIG. 11

is a perspective view of another embodiment of a tray handling system according to the present invention;





FIG. 12

is an end elevation of the tray handling system of

FIG. 11

, with the tray handling system extending along both sides of a pair of rows of mail sorters;





FIG. 13

is a side elevation of a portion of the tray handling system of

FIGS. 11 and 12

;





FIG. 14

is a top plan view of a portion of the tray handling system shown in

FIG. 13

; and





FIG. 15

is a perspective view of a linear actuator useful with the present invention, as positioned at a lower portion of a vertical tray moving device.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring now to the drawings and the illustrative embodiments depicted therein, an automatic tray handling system


10


is operable to provide empty trays


12




a


to a plurality of mail sorter units


14


of a sortation system


13


, and to remove at least partially filled trays


12




b


from the sorter units


14


after the trays are filled (FIGS.


1


and


2


). Although the invention is usable with a wide variety of mail or article sortation systems, it is illustrated with a model ASM100 flats mail sorter marketed in the United States by Rapistan Systems of Atecs Mannesmann AG. Automatic tray handling system


10


includes a plurality of conveying surfaces


16


, which are operable to move the trays


12


along one or both sides of the sorter units


14


. A plurality of tray moving devices


20


are operable at respective sorter units


14


to pull empty trays


12




a


onto a tray support


72


, which supports the empty tray while the sorter system discharges sorted mail into the tray. After the tray is at least partially filled by the sorter unit, the tray moving device


20


is then operable to move the at least partially filled tray back onto the conveying surface. Accordingly, the present invention provides a continuous supply of empty trays to the tray sorting units


14


, and automatically discharges filled or at least partially filled trays from the sorter units onto the conveying surface


16


, thereby substantially reducing the amount of manual labor processes required to replace filled trays with empty trays at each sorter unit.




Sorter units


14


of sortation system


13


are generally known and are commercially available, such that a detailed description of these devices is not included herein. Suffice it to say that each sorter unit


14


includes a bucket


14




a


, a sorting device


14




b


and a chute


14




c


. Unsorted mail or other articles are provided at the buckets


14




a


via a supply system (not shown), where the articles are then sorted by the sorting devices


14




b


and fall from the chute


14




c


into the bins or trays


12


. As shown in

FIG. 1

, an input end


11




a


of tray handling system


10


preferably provides one or more induct stations


38


and


40


for loading or inducting empty trays onto the tray handling system, while a discharge end


11




b


(

FIG. 2

) of tray handling system


10


provides a downstream operation, such as a labeling station


22


which is operable to label the trays as they are discharged from tray handling system


10


. The sorter units


14


may be arranged in a pair of rows, and the conveying surfaces


16


of automatic tray handling system


10


may extend around both sides of the rows of sorter units


14


. However, the principles of the present invention are equally applicable to a single side of a mail sortation system which has one or more rows of sorter units. Empty trays


12




a


are preferably movable in a continuous loop via conveying surfaces


16


and a pair of vertical tray moving or tray return devices


18


at one end of the tray handling system


10


(FIG.


2


). At least partially filled trays are conveyed from their respective sorter unit to labeling station


22


at discharge end


11




b


of tray handling system


10


.




As best seen in

FIGS. 1-5

, conveying surface


16


includes a plurality of conveying surfaces. More particularly, conveying surface


16


preferably includes a pair of opposite upper conveyors


24


and


26


, a pair of opposite lower conveyors


28


and


30


and a pair of tray moving or return devices, such as incline or connecting surfaces or ramps


32


and


34


, which are operable to move empty trays from lower conveyor


28


to upper conveyor


26


and from lower conveyor


30


to upper conveyor


24


, respectively, at input end


11




a


. A pop up belt transfer or 90 degree transfer


36


is positioned at each end of the incline ramps


32


and


34


to change the direction of travel of the trays


12


as they move from one of the lower conveyors to the respective incline ramp, and from the incline ramp to the respective upper conveyor. Such transfer units are commercially available and known in the art, such that a detailed discussion will not be included herein. Briefly, transfer units


36


are operable to convey a tray in a direction along the conveyor at which they are positioned, and may be operable to raise one or more belt conveyor strips to convey a tray positioned at the transfer unit in a direction which is generally transverse or normal to the conveyor direction.




Induct stations


38


and


40


are preferably positioned side by side one another, as shown in FIG.


1


. Preferably, induct stations


38


and


40


comprise belt conveyors, which are operable to transport or convey an empty tray onto a corresponding 90 degree transfer unit


36




a


and


36




d


, respectively. Empty trays may be manually or automatically loaded onto the induct stations to induct the empty trays into the conveyor system


16


of the automatic tray handling system


10


. Preferably, induct station


40


comprises an inclined belt conveyor, such that an input end


38


a and


40




a


of the induct stations


38


and


40


, respectively, are positioned at substantially the same level for easy access and loading of empty trays onto the induct stations


38


and


40


.




Similar to induct stations


38


and


40


, incline ramps


32


and


34


also preferably include belt conveyors, which are operable to move a continuous belt along the conveying path, as is know in the art. Incline ramp


32


is connected between a pair of 90 degree transfer units


36




a


and


36




b


at a downstream end


28




b


of lower conveyor


28


and an upstream end


26




a


of upper conveyor


26


, respectively. Similarly, incline ramp


34


is connected between a pair of 90 degree transfer units


36




c


and


36




d


at a downstream end


30




b


of lower conveyor


30


and an upstream end


24




a


of upper conveyor


24


, respectively.




Upper conveyors


24


and


26


are preferably powered roller conveyors, which include a plurality of rollers


42


which are rotatably mounted along and between a pair of side walls of


44




a


and


44




b


of each conveying surface


24


and


26


. The plurality of rollers


42


further includes multiple powered rollers


43


(FIG.


10


), which are also connected to the sidewalls


44




a


and


44




b


and driven via an internal motor to cause rotation of the powered roller relative to the wall, as is known in the art of roller conveyors. The powered rollers


43


are connected to a plurality of non-driven rollers


42


, such as to a pair of non driven rollers at either side of the powered roller


43


, via one or more bands or belts


45


(

FIGS. 8 and 10

) to define individually driven zones, as is known in the art. Preferably, the powered rollers


43


are mounted to the side walls


44




a


and


44




b


by an axle mounting yoke


46


(

FIG. 10

) of the typed disclosed in commonly assigned, co-pending U.S. pat. application, Ser. No. 09/418,297, filed Oct. 14, 1999 by Schiesser et al. for AXLE HOLDING YOKE FOR CONVEYOR ROLLER, now U.S. Pat. No. 6,367,617, the disclosure of which is hereby incorporated herein by reference. However, any known means for mounting the rollers to the sidewalls of the conveyors may be implemented without affecting the scope of the present invention. Preferably, as shown in

FIG. 3

, at least some of the rollers


42


and


43


are mounted to sidewalls


44




a


and


44




b


at an angle or skewed, in order to assist in moving the partially filled trays from the tray moving devices


20


onto upper conveying surfaces


24


,


26


, such that the tray may be moved along the respective upper conveying surface


24


,


26


. Although shown and described as roller conveyors, conveying surfaces


16


may otherwise include belt conveyors, belt/chain driven rollers, line shaft driven rollers or the like, without affecting the scope of the present invention.




As shown in

FIG. 2

, trays


12


are conveyed along upper conveying surfaces


24


and


26


toward a downstream end


24




b


and


26




b


, respectively. Vertical tray moving devices


18


are positioned near or at the downstream ends


24




b


and


26




b


to remove empty trays


12




a


from the upper conveyors and move the empty trays onto an upstream end


28




a


and


30




a


of the lower conveyors


28


and


30


, respectively, as discussed in detail below. Labeling stations


22


are positioned at or near a discharge end


24




c


and


26




c


of upper conveyors


24


and


26


, respectively, and are operable to label the filled trays as they are conveyed toward discharge end


11




b


of automatic tray handling system


10


. Preferably, one or both of the upper conveyors surfaces included a curved section


27


, such that the discharge ends


24




c


and


26




c


of upper conveyors


24


and


26


, respectively, are in close proximity, in order to reduce the manual labor of the system.




Preferably, a scanner


46


is positioned at discharge ends


24




c


and


26




c


to verify the information contained on the label applied to the trays. Preferably, a pair of reject conveyors


48


and


50


are provided adjacent to discharge ends


24




c


and


26




c


, respectively, to allow incorrectly labeled trays to be discharged to a separate area via respective 90 degree transfer units


36




e


and


36




f


and reject conveyors


48


and


50


.




Similar to upper conveyors


24


and


26


, lower conveyors


28


and


30


are preferably powered roller conveyors which include a plurality of driven rollers


43


and non-driven rollers


42


rotatably mounted to a pair of parallel walls or frames


44


. Lower conveyors


28


and


30


are preferably operable in a reverse direction from upper conveyors


24


and


26


, to return the empty trays


12




a


back toward input end


11




a


. The 90 degree transfer units


36




a


and


36




c


are positioned at downstream ends


38




b




30




b


and of conveyors


28


and


30


, respectively, to move the empty trays onto the respective incline ramps


32


and


34


to transport the trays to the upper conveyors


24


and


26


, respectively, at the other side of the sortation system


13


.




In order to provide a continuous loop for the empty trays about the conveyor surfaces


16


, vertical tray moving devices


18


are positioned at downstream ends


24




b


,


26




b


of upper conveyors


24


,


26


and upstream ends


28




a


,


30




a


of lower conveyors


28


,


30


. As best shown in FIGS.


3


and


5


-


8


, each vertical tray moving device


18


is operable to move an empty tray from the respective upper conveyor


24


,


26


, lower the tray to the level of the lower conveyors


28


,


30


, and then move the tray onto the respective lower conveyor


28


,


30


. Vertical tray moving device


18


includes an upper tray moving or pulling device


60


, a vertical tray moving or lowering device


62


and a lower tray moving or pushing device


64


, each of which is mounted to a frame or structure


66


. Because the vertical tray moving devices


18


move and lower only empty trays, the devices may include lightweight supports and moving members, since they are supporting and/or moving only the lightweight untilled trays, and need not include metal supports for strength in supporting the weight of filled trays.




Preferably, upper tray moving device


60


includes a driven belt, chain or the like


61


, which includes at least one engaging member


61


a for engaging and pushing and empty trays positioned at upper conveyor


24


,


26


in a direction generally transverse to the direction of conveyance of the upper roller conveyors. Belt


61


is reeved about a driven roller or wheel


60




a


, which is operable to rotate and thus cause movement of belt


61


, and a non-driven roller or wheel


60




b


spaced from driven wheel


60




a


and positioned generally over an opposite side of the respective upper conveyor


24


,


26


. Preferably, vertical tray moving device


18


includes a stop member


68


, which is operable to engage a forward side of an empty tray


12




a


and temporarily prevent movement of the empty tray


12




a


along upper conveyor


24


,


26


, while engaging member


61




a


engages and moves the empty tray


12




a


off of conveyor


24


,


26


and onto lowering device


62


. Stop member


68


may include a raisable or pivotable arm which may extend up between an adjacent pair of rollers at vertical tray moving device


18


to engage and stop an empty tray being conveyed along upper conveyors


24


,


26


. Optionally, a pop-up 90 degree transfer unit may be positioned along conveying surfaces


24


,


26


at vertical tray moving devices


18


to stop the empty trays at the conveyor and move the tray toward vertical tray moving device


18


, without affecting the scope of the present invention.




Lowering device


62


of vertical tray moving device


18


preferably includes a pair of belts, chains or the like


63


, each of which is reeved about a driven and non-driven wheel or roller


62




a


and


62




b


, respectively. Each belt


63


includes at least one, and preferably three, support members


63




a


, which receive the empty tray


12




a


thereon and support tray


12




a


while lowering the tray to the lower level. The driven wheels or rollers


62




a


are operable to rotate in an opposite direction relative to the other, with respect to the view of

FIG. 7

, such that support members


63




a


of each side of lowering device


62


are correspondingly moved in a downward direction to support and lower the empty tray


12




a


. Preferably, lowering device


62


includes the pair of belts and corresponding wheels/pulleys positioned at frame


66


, such that there is a gap


67


between the support members


63




a


of each lowering belt


63


.




Lower moving device


64


is positioned in gap


67


between lowering support members


63




a


and includes a continuous belt


65


, which is movable about a driven and non-driven roller


64




a


and


64




b


, respectively, such that at least one engaging member


65




a


contacts a side of empty tray


12




a


and pushes or otherwise moves tray


12




a


off of support members


63




a


of lowering device


62


and onto the respective lower conveying surface


28


,


30


. Preferably, as best shown in

FIG. 8

, lower conveyor


28


includes one or more, and preferably a pair of, shorter rollers


42


′ which are mounted to inner wall


44




a


of lower conveyor


28


, along with rollers


42


and


43


. Shorter rollers


42


′ are mounted at an outer end to an outer bracket


44




c


which is laterally inset from outer wall


44




b


, in order to provide clearance for lower tray moving device


64


, such that the empty tray may be moved out and fully onto the rollers


42


and


42


′ of lower conveyor


28


by lower tray moving device


64


.




Preferably, each tray moving device


60


,


62


and


64


of vertical moving devices


18


is operable to move the corresponding belt and engaging members in one direction. Each moving device preferably includes two or more engaging or support members along the respective belts, such that as one of the engaging or support members moves a tray via movement of the belts, another engaging or support member is correspondingly moved into position to engage or support the next empty tray. Upper tray moving device


60


is operable to move belt


61


in response to an empty tray being detected at vertical tray moving device


18


. Preferably, automatic tray handling system


10


is operable to identify and track filled or partially filled trays as they move along upper conveying surfaces


24


and


26


, as discussed below. The system is further operable to allow the tracked trays to pass by vertical tray moving devices


18


for labeling and discharge at discharge end


11




b


, while stopping empty or non-tracked trays at the vertical tray moving devices


18


. Optionally, vertical tray moving device


18


may include an optical sensor or scanner


70


to detect the tray and/or determine the status of the tray being conveyed along of the conveyors


28


and


30


, or may otherwise determine when a tray approaching the vertical tray moving device is an empty or filled tray, without affecting the scope of the present invention.




Preferably, vertical tray moving device


18


is first operable to raise or otherwise engage stop member


68


with the empty tray to prevent further movement along the upper conveyor, while engaging member


61




a


engages and pushes the tray off of the upper conveyor and onto the supports


63




a


of lowering device


62


. Lowering device


62


is then operable to lower the tray in response to the tray being positioned on the support member


63




a


. When activated, lowering device moves a predetermined amount to move the tray from the upper level to the lower level. Lower tray moving device


64


is then operable to move engaging member


65




a


into contact with the empty tray at the lower level to push the tray off of the lower support member


63




a


and onto shorter rollers


42


′ and adjacent rollers


42


of the lower conveyor. Lower moving device


64


is operable in response to the tray being detected at the lower level, or may be actuated subsequent to each actuation of lowering device


62


, which may also be automatically actuated subsequent to actuation of the upper tray moving device


60


.




Although shown and described as including movable belt devices for moving the tray off of the upper conveyor, lowering the tray to a level of the lower conveyor, and moving the tray onto the lower conveyor, clearly the scope of the present invention includes other means for automatically removing a tray from the upper conveyor and placing it at the lower conveyor, such as movable arms or bars which engage the tray and push/pull the tray in the desired direction or extendable and retractable devices which extend or retract to move the tray in the desired direction, or the like. It is further envisioned that vertical tray moving device may include one or more linear actuators


69


(FIG.


15


), which are operable to engage and move the empty tray from upper conveyer


24


,


26


and/or onto lower conveyor


28


,


30


, without affecting the scope of the present invention. Linear actuator


69


is preferably of the type disclosed in commonly assigned U.S. Provisional Pat. Application, Ser. No. 60/166,079, filed Nov. 17, 1999 for LINEAR ACTUATOR, by Schiesser et al., the disclosure of which is hereby incorporated herein by reference. Linear actuator


69


includes a carriage member


69




a


, which is slidable along a track or guide member


69




b


. The carriage


69




a


includes an engaging member


69




f


, which is operable to engage and move the empty tray toward and/or away from vertical tray moving device


18


, and in a direction generally normal to a direction of conveyance of the respective conveying surface


24


,


26


,


28


or


30


. For example, linear actuator


69


may be positioned within frame


66


at a lower end thereof, with engaging member


69




f


extending upwardly therefrom, and thus be operable to push the empty trays onto lower conveying surface


28


,


30


(as shown in FIG.


15


). Additionally, linear actuator


69


may be positioned at an upper end of frame


66


, with an engaging member extending downwardly from the carriage to engage an upper portion of the empty trays as they are conveyed along the upper conveying surface


24


,


26


. Carriage


69




a


is movable along guide member


69




b


in response to actuation of a linear motor or actuator


69




c


. Preferably, linear motor


69




c


is positioned at carriage


69




a


, while a conductor plate or strip


69




d


, which forms the secondary side of linear motor


69




c


, is secured along a surface


69




e


of guide member


69




b


. Preferably, linear motor


69




c


is a conventional linear motor such as a linear motor which is commercially available and manufactured by Mannesmann, Baldor/Normag and others.




Automatic tray handling system


10


is thus operable to move or convey empty trays throughout a continuous loop from one of the induct stations


38


,


40


. The empty trays are conveyed along the conveying surfaces


16


and moved by the vertical tray moving devices


18


until the empty tray is selected to be filled by one of the sorter units


14


. For example, an empty tray may be placed on induct station


38


and moved across lower conveyor


28


via 90 degree transfer unit


36




a


, up incline ramp


32


and onto upper conveyor


26


, via 90 degree transfer unit


36




b


. The empty trays conveyed along upper conveyor


26


, if not selected and captured by one of the moving devices


20


, as discussed below, are then vertically moved or returned down to lower conveyor


30


by one of the two vertical tray moving devices


18


. The empty tray is then conveyed back along lower conveyor


30


and onto the second incline ramp


34


via 90 degree transfer unit


36




c


. The tray is conveyed up the incline ramp


34


and onto upper conveyor


24


via 90 degree transfer unit


36




d


. If the empty tray is not selected for filling at one of the sorter units


14


along upper conveyor


24


, the empty tray is moved to lower conveyor


28


by the vertical tray moving device


18


, where the tray is again conveyed back along lower conveyor


28


and onto the first incline ramp


32


, thereby completing the loop of automatic tray handling system


10


.




Preferably, automatic tray handling system


10


further includes a pair of buffer conveyors


52


and


54


positioned along each inward side of lower conveyors


28


and


30


, respectively, and generally beneath the sorter units


14


, as best seen in

FIGS. 3 and 5

. Buffer conveyors


52


and


54


provide temporary storage for additional empty trays


12




a


, which may be discharged from buffer trays


52


,


54


onto upstream ends


28




a


,


30




a


of lower conveyors


28


,


30


, respectively, via a pair of 90 degrees transfer units


36




g


and


36




h


. Preferably, empty trays


12




a


may be inducted onto buffer conveyors


52


and


54


as the automatic tray handling system


10


attains full capacity of trays moving therealong. The empty trays may be discharged from buffer conveyors


52


and


54


onto lower conveyors


28


and


30


in response to a reduced number of trays being conveyed along conveying surfaces


16


, since additional trays may then be needed along tray handling system


10


.




Buffer conveyors


52


,


54


preferably include index chain drive conveyors, which may move an incremental amount in one direction to load one or more trays onto buffer conveyors


52


,


54


, and then may move an incremental amount in the opposite direction to discharge one or more trays onto lower conveyors


28


and


30


as needed. Buffer conveyors


52


,


54


are thus preferably operable in a last in, first out (LIFO) mode of operation, whereby the last tray to be inducted onto the buffer conveyors


52


,


54


is the first tray to be discharged therefrom as additional trays are needed along conveyors


16


of automatic tray handling system


10


. The buffer conveyors


52


,


54


thus provide additional capacity of trays for the system, such that empty trays


12




a


need not be inducted at induct stations


38


and


40


as rapidly in order to facilitate full capacity operation of automatic tray handling system


10


. Although shown and described as an index chain drive conveyor, clearly other conveying means may be implemented for the buffer conveyors, such as belt conveyors, roller conveyors or the like, without affecting the scope of the present invention. It is further envisioned that the buffer conveyor may receive empty trays at one end, such as at upstream end


28




a


,


30




a


of lower conveyors


28


,


30


, and discharge the trays at an opposite end, such as at downstream end


28




b


,


30




b


of lower conveyor


28


,


30


.




Referring now to

FIGS. 5

,


9


A and


9


B, tray moving devices


20


are positioned at each sorter unit


14


and are operable to stop an empty tray as it moves along the upper conveyor


24


or


26


and pull the tray onto a tray support


72


for filling at the respective sorter


14


. Each tray moving device


20


is further operable to move or push the filled or partially filled tray from the tray support


72


back onto the rollers


42


of the upper conveyor. Inner wall or bracket


44




a


for rollers


42


is secured along a frame or platform


74


, which provides an outer rail for attachment of outer wall


44




b


for mounting the opposite end of rollers


42


thereto. Tray moving device


20


includes a tray push/pull member


76


, a stop member


78


and tray support


72


. Preferably, tray stop member


78


includes a curved arm or bracket, which is pivotably mounted to a support bracket


80


, such that an upper end


78




a


of tray stop


78


is raisable between a pair of adjacent rollers


42


,


43


to engage and stop an empty tray from moving along the respective upper conveyor, while the tray push/pull member


76


engages and moves the tray off of the upper conveyor and onto the tray support


72


. Stop member


78


may be pivotable via any known means, such as by a rotary motor, a spring biased system, or any other means to raise stop member


78


, without affecting the scope of the present invention.




Preferably, as best seen in

FIG. 9B

, tray push/pull member


76


includes a pair of generally “U” shaped side frames


76




a


,


76




b


, which are interconnected at an upper end of each frame by a tray engaging or pulling member


76




c


at one end and a second tray engaging or pushing member


76




d


at the other end. Preferably, one side frame


76




b


of tray moving member


76


is slidably supported along frame


80


via a ball slide or track


82


or the like. The opposite side frame


76




a


is supported at one end by a wheel or roller


84


, which rotatably engages lower frame or platform


74


of the upper conveyor as the tray moving member


76


is extended and retracted therealong. An outer end


76




e


of side frame


76




a


is not supported by a roller or slide, in order to provide clearance over stop member


78


as the tray moving member


76


is moved outwardly, such that tray engaging member


76




c


is moved across and over the rollers


42


of the upper conveying surface.




Tray moving member


76


is preferably movable relative to frame


74


via a stepper motor


86


or the like. Stepper motor


86


includes a drive sprocket


86




a


, while frame


74


includes a cog sheave or spool


88


, such that a timing belt


90


is routed and movable about drive sprocket


86




a


and spool


88


in response to actuation of stepper motor


86


. As shown in

FIG. 9B

, timing belt


90


includes an attachment plate


90




a


, which is secured to side frame


76




b


of tray moving member


76


, such that movement of timing belt


90


results in a corresponding movement of tray moving member


76


. Clearly, however, other means for moving a tray stop and/or engaging member may be implemented without affecting the scope of the present invention.




As shown in

FIG. 9A

, tray support


72


provides a support platform


72




a


for supporting a tray while the tray is being filled by a respective sorter unit


14


. Because the filled trays are always supported by support


72


or conveyors


24


and


26


, the trays for use with the present invention need not require rigid side walls to withstand clamping or grabbing of the trays when they are filled. Tray support


72


is preferably formed such that a lower surface


72




b


is mountable to the platform of the upper conveyor while the sidewalls


72




c


and


72




d


are formed to provide clearance to stepper motor


86


and timing belt


90


and/or sideframes


76




b


and


76




a


of the tray moving member


76


. Preferably, tray support


72


further includes a transition roller


92


, which is rotatably mounted at tray support


72


and positioned between support platform


72




a


and rollers


42


,


43


of the upper conveying surface. Transition roller


92


is oriented generally normal to rollers


42


,


43


and is preferably positioned such that an upper surface of transition roller


92


is at a same level as an upper surface of the rollers


42


,


43


of the upper conveying surface. Transition roller


92


thus provides rolling support of the tray as it is moved between the upper conveying surface and the tray support platform


72




a


. Additionally, a tray guide member


94


may be positioned at an upper end of frame


74


and between a pair of adjacent tray supports


72


. Guide member


94


includes a tapered guide end


94




a


, which functions to assist in guiding the empty trays into proper position on the support surfaces


72




a


, as they are moved toward tray supports


72


by tray engaging members


76




c


of tray moving members


76


.




The present invention further includes a control system (not shown in detail), which is operable to actuate the driven rollers


43


of the conveying surfaces


16


and to actuate the tray moving devices


20


and the vertical tray moving devices


18


at appropriate times. Preferably, the control system is interconnected with a control system of the sortation system. The control system is operable to electronically identify a tray as it is being filled by a sorter unit and track the identified tray along upper conveying surfaces


24


and


26


. Tray handling system


10


is thus operable to allow the identified filled trays to move along the upper conveying surfaces past the vertical tray moving devices


18


, while empty trays, which are not electronically identified and tracked by the control system, are stopped and lowered by the vertical tray moving devices


18


. Additionally, the identification and tracking of the filled trays prevents the downstream tray moving devices


20


from stopping and filling an already filled tray, since such trays are identified and allowed to move along the conveying surface all the way to labeler


22


at discharge end


11




b


of tray handling system


10


. When the filled or at least partially filled trays arrive at the labeling station, the labelers


22


are operable to print a label and attach the label to the appropriate tray. As the tray proceeds along the conveying surface toward the discharge end, scanner


46


verifies that the information contained on the label matches the identification of that particular tray, and if the information is correct, the tray handling system allows the tray to continue towards the discharge end


24




c


,


26




c


of the conveying surface


24


,


26


. If incorrect label data is detected, the tray is transferred to the reject conveyors


48


and


50


via the transfer units


36




e


and


36




f


near the discharge end


24




c


and


26




c


of the conveying surfaces


24


and


26


, respectively.




When automatic tray handling system


10


is first started, the system must initially be charged or filled with empty trays. Preferably, empty trays are inducted onto the automatic tray handling system by manually placing the trays at one or both of the induction stations


38


and


40


at the upstream or induct end of the upper conveyors


24


,


26


. Alternately, or additionally, as shown in

FIG. 2

, empty trays may be inducted onto the upstream ends


28




a


and


30




a


of the lower conveying surfaces


28


and


30


via an induction station


19


at each vertical tray moving device


18


. Optionally, empty trays may be manually placed along the conveying surfaces


16


, such as along the lower conveying surfaces


28


and


30


. Initially, as empty trays are inducted into the system, empty trays are lowered by the vertical tray moving devices


18


onto the lower conveying surface, or input directly at induction stations


19


of moving devices


18


, and transferred across the lower conveying surfaces and into the buffer conveyors


52


and


54


via transfer units


36




g


and


36




h


at upstream ends


28




a


and


30




a


of lower conveyors


28


and


30


, respectively. The trays will be moved onto the buffer conveyors one tray position at a time until the buffer conveyors are approximately filled with trays. After the buffer conveyors are full, empty trays are continued to be loaded at the induction stations


38


and


40


and conveyed about the conveying surfaces


16


of the tray handling system


10


. Preferably, empty trays will be loaded into the tray handling system until the lower conveying surfaces


28


and


30


are both approximately 90 percent full. Alternately, for the preloading operation and for convenience, empty trays may be manually loaded directly onto the lower conveying surfaces


28


and


30


along their entire length or within 90 percent of their capacity.




Once the system is preloaded with empty trays, the normal operation of automatic tray a handling system


10


may begin. During normal operation, empty trays may be loaded onto the induct stations


38


and


40


or directly onto the lower conveying surfaces


28


or


30


. Preferably, the present invention is operable to release empty trays from the lower conveying surfaces


28


and


30


such that there is approximately a 10-foot gap between each adjacent pair of empty trays along upper conveying surfaces


24


and


26


. This provides a sufficient time delay between trays to allow time for the tray to be stopped and moved off of the conveying surface by the tray moving devices


20


or vertical tray moving devices


18


, and to allow sufficient space between consecutive empty trays for filled trays to be inducted onto the conveying surface from one of the sorter units. Based on a total machine normal output of five trays per minute, this gap ensures that nearly twice the required number of trays are made available during each minute of operation. The empty trays then are moved up the incline belts and onto the upper conveyor surfaces for selection and capture by the tray moving devices


20


at each sorter unit. The empty trays will automatically and continuously be conveyed toward the discharge end of the upper conveying surfaces until they are required to replace a discharged full tray at a sorter unit


14


. If the empty tray is not required or selected to replace a full tray, the empty tray will continue the loop via the vertical tray moving devices


18


, whereby they will accumulate on the lower conveying surface and cycle through the system again.




When a full tray is ready to be discharged from the sorter unit


14


, the control will wait until an empty tray passes the corresponding sorter unit and then will activate tray moving device


20


to push the full tray out onto the respective upper conveying surface


24


or


26


. The tray moving device


20


is operable to lower the stop arm


78


out of the way at the end of its push cycle to allow the full tray to convey toward the discharge end of the upper conveying surface


24


or


26


. As soon as the full tray is clear of the stop member


78


, the stop member


78


is again operable to raise and capture the next oncoming and/or available empty tray, such that the tray moving device may pull the empty tray onto the tray support


72


for filling by the corresponding sorter unit. The filled trays are then conveyed along the upper conveying surfaces


24


,


26


and are labeled and discharged at discharge end


11




b


of tray handling system


10


.




Preferably, as a tray is discharged from a particular sorter unit


14


, the control selects and reserves the next available empty tray inducted onto the conveying surfaces


16


for that particular sorter unit. The sorter unit may not capture the next empty tray that passes thereby, since this tray may already be selected and reserved for another sorter unit which discharged its filled tray prior to the other sorter unit. Accordingly, the control is preferably operable in a “first come, first served” mode of operation which precludes a sorter unit at a downstream end of one of the upper conveying surfaces


24


and


26


from waiting a prolonged period of time until an empty tray is not captured at any of the upstream sorter units. Any empty trays not captured and filled by any of the sorter units during the pass in front of the sorter units will be transferred onto the lower conveyor units


28


and


30


via the vertical tray moving devices


18


located at the downstream end of the upper conveyors


24


and


26


. The empty trays are repeatedly conveyed about the continuous loop of conveying surfaces


16


until the empty tray is captured and filled at one of the sorter units


14


of sortation system


13


.




The present invention is also operable in a sweep process, whereby the tray handling system is purged of filled and/or partially filled trays and each sorter unit is provided with a new empty tray. During the sweep process, the mail delivery or supply system will deliver all of the inducted mail to the sorters or into.a reject bin. As the mail is delivered during the sweep process, no additional empty trays will be released from the respective lower conveying surfaces


28


or


30


, such that the upper conveying surfaces


24


and


26


can be cleared of empty trays. All of the full trays will then be discharged from their respective sorter unit onto the upper conveying surfaces and conveyed to the labeler for labeling and discharge from the automatic tray handling system. After all of the at least partially filled trays have been discharged from the system, empty trays will be released and will be captured and pulled onto tray supports at each sorter unit, preferably in the order that the empty trays encounter the sorter unit, until all of the sorter units have been replenished with empty trays. As soon as the bins have been replenished with empty trays, the next sorting cycle can begin. Any full trays remaining on the upper conveying surfaces


24


and


26


will continue toward the labelers. Once the final remaining full trays are clear of the labelers, the empty trays will again be allowed to re-circulate through the automatic tray handling system as described above. Preferably, the lower conveyors


28


and


30


and the buffer conveyors


52


and


54


hold a sufficient number of empty trays to facilitate replenishing of empty trays at each mail sorter


14


without requiring additional empty trays to be manually inducted onto the system during a sweep operation.




Although shown and described as having a continuous loop along both sides of the sortation system


13


, it is envisioned that the incline ramps


32


and


34


of tray handling system


10


may be replaced by an empty tray raising device, without affecting the scope of the present invention. The empty tray raising devices are then operable to remove empty trays from the downstream end of lower conveying surfaces, raise the trays upward, and induct or return the empty trays onto the upstream end of the upper conveying surfaces, in a similar manner that the trays are lowered by the vertical tray moving devices


18


. The empty trays would then be movable about a separate continuous loop along each side of sortation machine or system.




Referring now to

FIGS. 11-14

, an automatic tray handling system


100


is operable to move empty trays


112




a


from an empty tray conveyor


128


to an appropriate mail sorter


114


for filling, and then to move the at least partially filled trays


112




b


from the mail sorter onto a full tray takeaway conveyor


124


. Preferably, empty tray conveyor


128


is positioned along and below full tray conveyor


124


, such that the empty trays are moved upwardly from a lower level to an upper level at the sorter units


114


by a tray moving device


120


positioned at each sorter unit


114


. However, the empty tray conveyor may be positioned above the full tray take away conveyor, without affecting the scope of the present invention. Preferably, automatic tray handling system


100


is applicable to a sortation system


113


, which includes one or more rows of sorter units


114


, similar to sortation system


13


, discussed above and as known in the art. An upper, full tray conveyor


124


and a lower, empty tray conveyor


128


are then positioned along each row of sorter units at each side of sortation system


113


.




Both of the empty tray conveyor


128


and full tray conveyor


124


preferably comprise powered roller conveyors, similar to upper and lower conveying surfaces


24


,


26


,


28


and


30


, discussed above. Preferably, as best shown in

FIG. 14

, several of the rollers


142


of the upper, full tray conveyor


124


are angled or skewed along the conveyor path to assist the tray handling system in moving the full tray out from the sorter unit and onto the upper conveyor


124


.




Automatic tray handling system


100


preferably includes at least one induction station (not shown) positioned at an induct end or upstream end of empty tray conveyor


128


, while a labeling and discharge area (also not shown) are positioned at a downstream or discharge end of each upper full tray conveyor


124


. Preferably, the induct stations, labelers and discharge stations are substantially similar to induct stations


38


,


40


, labelers


22


, and discharge end


11




b


of automatic tray handling system


10


, discussed above, such that a detailed description will not be repeated herein. As the operators are loading the empty trays onto the induct stations, the operators may orient the trays such that a label holder is properly positioned to receive the label onto the tray at the labeling station at the discharge end of the tray handling system.




Tray moving devices


120


are positioned at each sorter unit


114


along the conveying surfaces


124


and


128


. Each tray moving device


120


is operable to stop an empty tray moving along empty tray conveyor


128


, pull the empty tray onto a tray support or tray lifter


163




a


and raise the empty tray upward to position the empty tray under the corresponding sorter unit for filling of the empty tray. After the tray is filled, the tray moving device is again operable to push or otherwise move the filled tray onto the upper full tray take away conveyor


124


, whereby the full tray is conveyed along the conveyor to the labeler at the discharge end of the conveyor. As best shown in

FIGS. 12 and 13

, each tray-moving device


120


includes a lower tray-pulling device


160


, a vertical tray moving device


162


and an upper tray-pushing device


164


. Each tray moving device


120


further includes a stop member


178


, which is operable to raise between a pair of adjacent rollers along empty tray conveyor


128


to stop an empty tray, while lower tray pulling device


160


engages and pulls the empty tray onto the tray support


163




a


. Tray stop


178


may include a pivotable arm similar to stop member


78


discussed above, or may be any other means for stopping a tray along the conveyor, without affecting the scope of the present invention. It is further envisioned that the trays may be otherwise stopped at each targeted location along empty tray conveyor


128


via actuation and deactuation of individual powered roller zones which convey the tray along conveyor


128


and thus may be individually operable to stop the tray at a selected zone, without affecting the scope of the present invention.




Preferably, lower tray pulling device


160


includes an engaging arm


161


, which is extendable to engage an opposite side of the empty tray from the tray moving device


120


and is retractable or otherwise movable toward the tray moving device


120


, thereby engaging the opposite side of the empty tray and pulling the empty tray toward the moving device


120


. Lower tray pulling device


160


may be movable via any know means, such as via a driven belt, similar to tray moving device


60


discussed above, or via a linear actuator


169


(FIG.


13


), similar to linear actuator


69


discussed above and shown in FIG.


15


. Lower tray moving or pulling device


160


may be mounted at the tray moving device


120


, or may otherwise be movably mounted along and between a pair of adjacent rollers at the empty tray conveyor


128


. As best shown in

FIG. 14

, each tray moving device


120


further includes a guide member


194


, which functions to guide the empty tray into position on the supports


163




a


, such that the empty tray is properly oriented for receiving the sorted mail from the sorter unit


114


.




Once an empty tray has been pulled from the empty tray conveyor


128


and onto tray support


163




a


, vertical tray raising device


162


is operable to raise the supports


163




a


and thus the empty tray upward into position immediately beneath the chute


114




c


of the associated sorter unit


114


. Preferably, vertical tray raising device


162


includes a vertical ball/screw actuator


163


, which is operable to rotate a threaded shaft


162




b


to raise tray support


163




a


via engagement with a threaded connector


163




c


at tray supports


163




a


. Tray supports


163




a


are preferably a pair of L-shaped metal support arms which support the trays at a lower arm


163




d


of support arm


163




a


, while an upper arm


163




e


is mounted to the vertical tray moving device


162


. Vertical tray moving device


162


is thus operable to raise the tray upwardly and to support the empty tray as the empty tray is filled by the corresponding sorter unit


114


. Accordingly, the tray supports


163




a


must have sufficient strength to support the weight of a filled tray.




After the tray has been filled by the sorter unit


114


, upper tray moving or pushing device


164


is operable to push or otherwise move the filled tray from the support


163




a


onto the upper, full tray take away conveyor


124


. Upper tray moving device


164


preferably includes an integral motor operated pusher


165


and is mounted at support


163




a


, as shown in FIG.


13


. The pusher or tray engaging member


165


may be movable along a chain, belt or linkage


165




a


via a pair of driven and guide wheels


165




b


, similar to tray moving device


64


, discussed above. Preferably, the engaging member


165


engages a lower portion of the trays, as shown in

FIG. 12

, to prevent tipping of the filled tray as it is moved onto upper conveyor


124


. After the filled tray has been moved onto the upper conveying surface


124


, tray moving device


164


is operable to reverse the direction of movement of the engaging member


165


to return the engaging member to an initial position at an inward side of the tray support


163




a


. Because upper tray moving device


164


is operable to move a filled tray onto the upper conveying surface


124


, tray moving device


164


must be sufficiently durable and powerful to engage and move the filled trays from the supports


163




a


onto the conveying surface


124


. Although shown as a chain driven engaging member, the moving device


164


may include any known means for moving the tray from the support surface


163




a


onto the conveying surface


124


, without affecting the scope of the present invention.




Automatic tray handling system


100


includes an integrated software and control system which is designed to track filled trays from each of the sorter units to the labeling system at a discharge end of the tray handling system, in order to ensure that the correct label is applied to the appropriate tray. A scanner (not shown) is provided to scan the applied label and confirm that the correct label was applied to the appropriate tray. If the label is not correct, the tray is diverted to a reject area, where a signal may be provided to notify an operator that the tray was mislabeled.




During operation, automatic tray handling system


100


is operable to move empty trays along the empty tray conveyor


128


positioned at one or both sides of the sortation system


113


. Preferably, empty mail trays are inducted onto the empty tray conveyors and staged at every third bin or sorter unit such that they are positioned to provide optimum clearance and gapping for proper tray transferring, and to avoid potential interference between trays. When an empty tray is called for at one of the bin or sorter units which does not have a tray positioned thereby, the tray stop members, which are operable to retain an empty tray at a upstream position along the empty tray conveyor


128


, will release the empty tray and allow the tray to advance to the desired position. The tray stop member


178


of tray moving device


120


will stop the empty tray at the appropriate sorter unit and lower tray moving device


160


will move the empty tray onto the tray supports


163




a


for raising the tray to the sorter unit. After the empty tray is raised into position under chute


114




c


, the empty tray is then filled by the sorter unit until the control system indicates that the tray has been filled. Once the tray is filled, the upper tray moving device


164


is operable to move the filled tray onto the full tray take away conveyor, provided there is no full tray present in the transfer path. After the upper tray moving device


164


returns to its initial position, the vertical tray moving device


162


will lower the supports


163




a


and prepare to accept another empty tray from the empty tray conveyor


128


and lower tray moving device


160


.




The control system of the automatic tray handling system are operable to prevent any interference between oncoming trays on the upper conveyor


124


and full trays ready to be discharged from the tray Supports and sorter units. When a tray becomes filled by the particular sorter at which it is positioned, the flat sorter unit will communicate to the automatic tray handling system controller that the tray must be removed. When a tray is destined to exit the sorter unit, and an open position is available on the filled tray conveyor


124


, the upstream trays will be held in position along the conveyor


124


until the tray leaving the particular sorter unit is moved onto the conveyor


124


. Once the tray is in position on the conveyor, all of the trays may continue to move toward the label printer. If a tray is ready to leave the sorter and an open position is not available on the take away conveyor


124


, such as because another tray is moving into position, the full tray will be held at the sorter unit until the position is cleared.




The control system identifies and acknowledges discharged full trays along the full tray conveyor


124


, and is operable to track the full trays along the length of the full tray conveyor


124


to the automatic labeling system located at the discharge end of the conveyor. Preferably, each sorter unit is positioned at an individual zone or section of the powered roller conveyor


124


which consists of its own powered zone and sensor assembly, thereby facilitating individual zone-to-zone tracking of trays by the control. The tray tracking system of the present invention is operable to ensure that the filled tray has the proper label attached to it at the label printers. Accordingly, the trays must be tracked from their sort location to the labeler. Each filled tray is electronically identified with appropriate destination data by the sorter machine software before the tray leaves the respective sorter unit. After the sort schedule is determined, the software will communicate to the automatic tray handling system controller which output bin destinations are dedicated to each sort location on the sortation system. The data can then be tracked with the tray when it is discharged from the sorter unit.




Preferably, each tracking zone is associated with a particular sorter unit and is independently controlled. Each zone also may utilize a photo eye or sensor to identify the tray position along the conveyor. Whenever a full tray is discharged from a sorter unit onto the full conveyor


124


, the output bin destination data is electronically moved with the tray, as the tray is conveyed toward the automatic label printer. The tray will be conveyed into the next zone or zones if those zones are not occupied by another tray. The tray continues to be conveyed along the full tray conveyor


124


as long as the next downstream zone is clear or vacant. When the filled tray reaches the label printer, the control of the automatic tray handling system


100


is operable to communicate to the label printer which label data must be printed for that particular tray. The correct label will then be printed and affixed to the tray. A scanner (not shown) may be provided to scan a bar code on the printed label once it has been printed and applied, in order to verify that the label is correct for that particular tray.




If the sensor or photo eye detects a tray positioned at a particular zone for a prolonged period of time, the system is operable to detect a jam in the conveyor. When a jam has been detected, the system is operable to hold all of the upstream trays until the jam has been cleated and the system reset. Preferably, the system is also operable to detect a missing tray if a tray is removed, to detect a tray that does not belong in that particular zone, or to detect an extra tray that has been placed on the filled tray conveyor


124


. The extra tray will be sent to the reject area until the tray's data can be accounted for.




Automatic tray handling system


100


is also operable to perform a sweep process to clear the full trays from the system. During the sweep process, the empty trays staged at every third position along the empty tray conveyor


128


are advanced to close gaps, while any required additional trays may be fed into the conveyor at the induct stations. As part of the sweep process, any remaining mail in the mail supply and/or sortation system must be sorted to the appropriate bins before any full trays can be swept. Once the message is received that the sort is complete and all remaining mail has been discharged from the sorting system buckets, the full tray sweep process can begin.




Because of clearance issues along the full tray conveyor


124


, full trays at every other sorter unit are initially discharged. The upper tray moving devices


164


are operable to substantially simultaneously push or extend the full trays


112




b


onto full tray conveyor


124


. When the tray moving devices


164


retract, the vertical tray moving devices


162


are operable to lower the supports


163




a


to position the supports at a lower level to accept empty trays from the empty tray conveyor


128


. The first half of the filled trays are then advanced toward the automatic labeler, while empty trays along the empty tray conveyor


128


are simultaneously transferred onto the respective supports


163




a


. While the empty trays are lifted into the first group of empty sorter units, and while the last tray of the preceding group passes the sorter unit at the downstream end of the conveyors, the second group of filled trays from the other sorter units are discharged onto the full tray conveyor


124


. Similar to the first set, as soon as the tray moving devices


164


return, the empty tray replenishment process is repeated for the second group of sorter units. While the second group of trays are being pushed out, the empty trays are staged simultaneously, such that the empty trays are positioned to be pulled onto the supports


163




a


for the second group of sorter units.




Accordingly, the present invention provides an automatic tray handling system that is especially useful with automated article sorting machines, such as flats mail sorting machines. However, the invention could be used with other sorters such as letter mail sorters and the like, without affecting the scope of the present invention. The present invention is thus operable to deliver empty trays to any and all of the sorter units of the sortation system and further is operable to automatically convey full trays to the labeling stations. The tray handling system of the present invention is operable to deliver empty trays to individual sorter units and remove filled trays from the sorter units, whereby the filled trays are conveyed to downstream operations, such as a labeling station, at a discharge end of the tray handling system. The only manual intervention that may be required is to manually induct multiple empty trays into the system, whereby the tray handling system conveys and stages the trays for filling at the appropriate sorter units. The present invention is designed to be adapted for implementation with conventional or known sorting machines, such that the present invention may be retrofitted to existing units with minimal changes required to the sorting machine unit.




Additionally, the automatic tray handling system of the present invention provides a safe working environment for operators and maintenance personnel, while at the same time maintaining ready access to the sorter units of the sorting machine. The automatic tray handling system is also configured to minimize space taken up around the sorter machines.




The control system of the present invention further facilitates electronic tracking of trays along the conveyors between the sorter units and the labeling stations. After a label is applied to the tray, the label may be scanned to verify that the label was printed properly for that particular tray. The present invention is preferably tied into the controls of the sortation system, such that the sortation system can communicate to the tray handling system when a particular tray has been filled and when an empty tray is needed at each of the sorter units of the sortation system.




Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law.



Claims
  • 1. An automatic tray handling system adapted for use with a flats mail sorter, said automatic tray handling system comprising:a plurality of tray filling areas positioned at a plurality of tray filling devices, said tray filling devices being operable to at least partially fill trays positioned at said plurality of tray filling areas with sorted articles received from a mail sorter; at least one conveying surface which is operable to convey at least one of empty trays and at least partially filled trays generally adjacent to said tray filling areas; and a plurality of tray moving devices which are operable to move empty trays from said at least one conveying surface to said tray filling areas and to move at least partially filled trays from said tray filling areas to said at least one conveying surface, said at least one conveying surface defining a closed path, at least a portion of said at least one conveying surface being generally adjacent to said tray filling areas, said at least one conveying surface being operable to recycle empty trays around said closed path.
  • 2. The automatic tray handling system of claim 1, wherein both the empty and at least partially filled trays are conveyed along the same surface of said at least one conveying surface.
  • 3. The automatic tray handling system of claim 1, wherein said at least one conveying surface comprises a first conveying surface and a second conveying surface, said second conveying surface being operable to convey empty trays therealong.
  • 4. The automatic tray handling system of claim 3, wherein said first conveying surface is positioned above said second conveying surface.
  • 5. The automatic tray handling system of claim 3, wherein said first conveying surface is operable to convey both empty trays and at least partially filled trays therealong.
  • 6. The automatic tray handling system of claim 1, wherein said tray moving devices are operable to move empty trays via at least one linear actuator.
  • 7. The automatic tray handling system of claim 1, wherein said at least one conveying surface comprises at least one of a continuous belt conveyor surface and a motorized roller conveying surface.
  • 8. The automatic tray handling system of claim 1, wherein each of said plurality of tray moving devices is operable to stop an empty tray which is moving along said at least one conveying surface and pull the empty tray in a direction generally transverse to said at least one conveying surface and toward a corresponding one of said tray filling areas.
  • 9. The automatic tray handling system of claim 1, wherein said tray moving devices are operable to move empty trays to said tray filling areas in response to the respective tray filling area being available to receive an empty tray.
  • 10. The automatic tray handling system of claim 1, wherein each of said plurality of tray moving devices is movable to move empty trays to said tray filling areas in an order in which said tray filling areas become available.
  • 11. The automatic tray handling system of claim 1, wherein said tray handling system is operable to convey empty trays along said closed path of said at least one conveying surface along said tray filling areas until the empty tray is selected and moved by said tray moving device from said at least one conveying surface to a respective one of said tray filling areas.
  • 12. The automatic tray handling system of claim 1, wherein at least one of the empty trays and the at least partially filled trays are electronically tracked along said at least one conveying surface.
  • 13. The automatic tray handling system of claim 1, wherein said tray moving device is operable to move an at least partially filled tray onto said at least one conveying surface in response to identification of a gap between trays along said at least one conveying surface.
  • 14. An automatic tray handling system for use with a mail sorter, said automatic tray handling system comprising:a plurality of tray support areas positioned at a plurality of tray filling devices, said tray filling devices being operable to at least partially fill trays supported at said plurality of tray support areas with sorted articles received from a mail sorter; at least one conveying surface which is operable to convey at least one of empty trays and at least partially filled trays generally adjacent to said tray support areas, said at least one conveying surface comprising a first conveying surface and a second conveying surface, said second conveying surface being operable to convey empty trays therealong; a plurality of tray moving devices which are operable to move empty trays from said at least one conveying surface to said tray support areas and to move at least partially filled trays from said tray support areas to said at least one conveying surface; and at least one tray return device which is operable to move empty trays between said first and second conveying surfaces.
  • 15. The automatic tray handling system of claim 14, wherein said at least one tray return device is operable to move empty trays via at least one linear actuator.
  • 16. An automatic tray handling system for use with a mail sorter which includes two rows of sorter units, said automatic tray handling system comprising:a plurality of tray filling areas positioned at a plurality of tray filling devices, said tray filling devices being operable to at least partially fill trays positioned at said plurality of tray filling areas with sorted articles received from a mail sorter, wherein said automatic tray handling system includes two rows of said tray filling areas, said tray filling devices and said tray moving devices being positionable along each side of the mail sorter; at least one conveying surface which is operable to convey at least one of empty trays and at least partially filled trays generally adjacent to said tray filling areas; and a plurality of tray moving devices which are operable to move empty trays from said at least one conveying surface to said tray filling areas and to move at least partially filled trays from said tray filling areas to said at least one conveying surface, said at least one conveying surface defining a closed path, at least a portion of said at least one conveying surface being generally adjacent to said tray filling areas, said at least one conveying surface being operable to recycle empty trays around said closed path.
  • 17. The automatic tray handling system of claim 16, wherein said at least one conveying surface is operable to convey empty trays along both rows of said tray filling areas.
  • 18. An automatic tray handling system for use with a mail sorter, said automatic tray handling system comprising:a plurality of tray filling areas positioned at a plurality of tray filling devices, said tray filling devices being operable to at least partially fill trays positioned at said plurality of tray filling areas with sorted articles received from a mail sorter; at least one conveying surface which is operable to convey at least one of empty trays and at least partially filled trays generally adjacent to said tray filling areas; and a plurality of tray moving devices which are operable to move empty trays from said at least one conveying surface to said tray filling areas and to move at least partially filled trays from said tray filling areas to said at least one conveying surface, said at least one conveying surface defining a closed path, at least a portion of said at least one conveying surface being generally adjacent to said tray filling areas, said at least one conveying surface being operable to recycle empty trays around said closed path, wherein said at least one conveying surface includes a discharge section for discharging at least partially filled trays from said closed path, at least partially filled trays being transferred to a labeling device at said discharge station.
  • 19. The automatic tray handling system of claim 18, wherein the at least partially filled trays are electronically identified at at least one of the mail sorter and said at least one conveying surface, said labeling device being operable to label the identified trays with appropriate information.
  • 20. An automatic tray handling system for use with an article sorter having a plurality of sorter units and a plurality of tray support areas for positioning a tray at a sorter unit while the tray is being filled with sorted articles, said automatic tray handling system comprising:a first conveying surface which is operable to convey at least one of empty trays and at least partially filled trays generally adjacent to the tray support areas; a second conveying surface which is operable to convey empty trays therealong, said first conveying surface being positioned along and generally above said second conveying surface; at least one tray return device which is operable to move trays between said first conveying surface and said second conveying surface; and at least one tray moving device which is operable to move empty trays generally horizontally from one of said first and second conveying surfaces toward the tray support area and to move partially filled trays generally horizontally from the tray support area toward said first conveying surface.
  • 21. The automatic tray handling system of claim 20, wherein said at least one tray return device comprises multiple tray return devices and said at least one tray moving device comprises multiple tray moving devices, one of said tray return devices and one of said tray moving devices being positioned at each of the plurality of tray support areas.
  • 22. The automatic tray handling system of claim 21, wherein said tray moving device is operable to move empty trays generally horizontally from said second conveying surface, said tray return device being operable to then move the empty trays generally vertically toward said second conveying surface.
  • 23. The automatic tray handling system of claim 20, wherein said tray return device is operable to move empty trays from said first conveying surface generally downwardly to said second conveying surface.
  • 24. The automatic tray handling system of claim 23, wherein said tray moving device is operable to move empty trays from said first conveying surface toward the tray support area and to move at least partially filled trays from the tray support area toward said first conveying surface.
  • 25. The automatic tray handling system of claim 20, wherein the article sorter includes two rows of sorter units, said automatic tray handling system being positioned along both rows of sorter units.
  • 26. The automatic tray handling system of claim 25, wherein said automatic tray handling system is operable to convey empty trays in a generally continuous loop along both rows of sorter units.
  • 27. The automatic tray handling system of claim 26, wherein said first conveying surface on one side of the article sorter is connected to said second conveying surface on the other side of the article sorter via a third conveying surface.
  • 28. The automatic tray handling system of claim 27, wherein said third conveying surface is positioned between an upstream end of said first conveying surface on the one side and a downstream end of said second conveying surface on the other side.
  • 29. The automatic tray handling system of claim 28, wherein said tray return device is operable to move empty trays from a downstream end of said first conveying surface to an upstream end of said second conveying surface at each side of the article sorter.
  • 30. The automatic tray handling system of claim 20, wherein said automatic tray handling system is operable to convey empty trays in a generally continuous loop along the sorter units.
  • 31. The automatic tray handling system of claim 20, wherein said automatic tray handling system is adapted for use with a flats mail sorter.
  • 32. An automatic tray handling system for use with an article sorter including a plurality of sorter units and a plurality of corresponding tray support areas for positioning a tray while the tray is being filled with sorted articles, said automatic tray handling system comprising:at least one first tray conveying surface which is operable to convey at least empty trays and partially filled trays along the tray support areas; at least one second tray conveying surface which is operable to convey at least empty trays generally along the tray support areas; at least one first tray return device which is operable to move empty trays from said at least one second tray conveying surface to said at least one first tray conveying surface; at least one second tray return device which is operable to move empty trays from said at least one first tray conveying surface to said at least one second tray conveying surface; and a plurality of tray moving devices which are operable to move empty trays from said at least one first tray conveying surface to the tray support areas, to support the trays at the tray support areas, and to move at least partially filled trays from the tray support areas to said at least one first tray conveying surface.
  • 33. The automatic tray handling system of claim 32, wherein said first tray conveying surface and said second tray conveying surface comprise powered roller conveying surfaces and said first tray return device comprises a continuous belt conveying surface.
  • 34. The automatic tray handling system of claim 32, wherein said at least one first tray conveying surface is positioned along and above said at least one second tray conveying surface.
  • 35. The automatic tray handling system of claim 32, wherein the article sorter includes two rows of sorter units, said automatic tray handling system being positioned along each side of the article sorter.
  • 36. The automatic tray handling system of claim 35, wherein said at least one first tray return device is operable to move empty trays from a downstream end of said second tray conveying surface on one side of the mail sorter to an upstream end of said first tray conveying surface on an opposite side of the mail sorter.
  • 37. The automatic tray handling system of claim 36, wherein said at least one first tray return device comprises a connecting conveying surface between said downstream end of said second tray conveying surface and said upstream end of said first tray conveying surface.
  • 38. The automatic tray handling system of claim 35, wherein said automatic tray handling system is operable to move empty trays in a generally continuous loop along both rows of sorter units.
  • 39. The automatic tray handling system of claim 32, wherein said automatic tray handling system is operable to move empty trays in a generally continuous loop at the mail sorter.
  • 40. The automatic tray handling system of claim 32, wherein said at least one first tray return device is operable to move empty trays from said at least one second tray conveying surface to an upstream end of said at least one first tray conveying surface.
  • 41. The automatic tray handling system of claim 32, wherein said at least one second tray return device is operable to move empty trays from a downstream end of said at least one first tray conveying surface to said at least one second tray conveying surface.
  • 42. The automatic tray handling system of claim 32, wherein said second tray return device is operable to stop empty trays as the empty trays are conveyed along said first tray conveying surface, while allowing partially filled trays to be conveyed past said second tray return device toward a discharge end of said first tray conveying surface.
  • 43. The automatic tray handling system of claim 42, wherein said at least one second tray return device is operable to stop an empty tray which is moving along said first tray conveying surface, move the empty tray in a direction generally transverse to a direction of conveyance of said first tray conveying surface, lower the empty tray to a level of said second tray conveying surface and move the empty tray onto said second tray conveying surface.
  • 44. The automatic tray handling system of claim 32 further including at least one buffer conveying surface which is operable to at least temporarily hold at least one empty tray, said buffer conveying surface being further operable to induct an empty tray onto said at least one second tray conveying surface.
  • 45. The automatic tray handling system of claim 44, wherein said at least one buffer conveying surface is operable to move empty trays onto said second conveying surface in response to a reduced number of empty trays on said second conveying surface.
  • 46. The automatic tray handling system of claim 45, wherein said at least one buffer conveying surface comprises an indexing chain conveyor.
  • 47. The automatic tray handling system of claim 32, wherein each of said tray moving devices is operable to stop an empty tray as the empty tray is conveyed along said first tray conveying surface.
  • 48. The automatic tray handling system of claim 47, wherein said at least one first tray conveying surface comprises a motorized roller conveyor which includes a plurality of rollers, each of said plurality of tray moving devices including a stop member which is raisable between an adjacent pair of said rollers, said stop member being operable to stop an empty tray when the empty tray is adjacent to a targeted tray support area.
  • 49. The automatic tray handling system of claim 48, wherein each of said plurality of tray moving devices further includes a first moving member which is operable to engage the empty tray and move the stopped empty tray to the targeted tray support area.
  • 50. The automatic tray handling system of claim 49, wherein each of said plurality of tray moving devices further includes a second moving member which is operable to engage an at least partially filled tray at a corresponding tray support area and move the partially filled tray from the tray support area onto said at least one second tray conveying surface.
  • 51. The automatic tray handling system of claim 32, wherein said automatic tray handling system is adapted for use with a flats mail sorter.
  • 52. A method for handling trays for use with a mail sorter, said method comprising:providing a plurality of tray filling areas and tray filling devices along a mail sorter, said tray filling areas being configured to position trays while said tray filling devices at least partially fill the trays with sorted articles from the mail sorter; providing at least one conveying surface at least partially along said plurality of tray filling areas; conveying empty trays along said at least one conveying surface; moving empty trays from said at least one conveying surface to said tray filling areas; at least partially filling the empty trays at said tray filling areas; moving partially filled trays from said tray filling areas onto said at least one conveying surface; recycling empty trays along said at least one conveying surface in a generally continuous loop until the empty trays are moved to said tray filling areas; and conveying the partially filled trays to a labeling station after the partially filled trays are moved onto said at least one conveying surface.
  • 53. The method of claim 52 further including tracking the at least partially filled trays as they are conveyed from said tray filling areas to said labeling station.
  • 54. The method of claim 53 further including labeling the at least partially filled trays at said labeling station.
  • 55. The method of claim 54 further including verifying that an appropriate label is affixed to the at least partially filled trays after the trays are labeled at said labeling station.
  • 56. A method for handling trays for use with a mail sorter, said method comprising:providing a plurality of tray filling areas and tray filling devices along a mail sorter, said tray filling areas being configured to position trays while said tray filling devices at least partially fill the trays with sorted articles from the mail sorter; providing at least one conveying surface at least partially along said plurality of tray filling areas, wherein said conveying surface comprises first and second conveying surfaces, said first conveying surface being positioned along and generally above said second conveying surface; conveying empty trays along said at least one conveying surface; moving empty trays from said at least one conveying surface to said tray filling areas; at least partially filling the empty trays at said tray filling areas; moving partially filled trays from said tray filling areas onto said at least one conveying surface; and recycling empty trays along said at least one conveying surface in a generally continuous loop until the empty trays are moved to said tray filling areas.
  • 57. A method for handling trays for use with a mail sorter, said method comprising:providing a plurality of tray support areas and tray filling devices along a mail sorter, said tray support areas being configured to position trays while said tray filling devices at least partially fill the trays with sorted articles from the mail sorter; providing at least one conveying surface along said plurality of tray support areas, wherein said at least one conveying surface comprises first and second conveying surfaces, said first conveying surface being positioned along and generally above said second conveying surface; conveying empty trays along said at least one conveying surface; moving empty trays from said at least one conveying surface to said tray support areas; at least partially filling the empty trays at said tray support areas; moving partially filled trays from the tray support area onto said at least one conveying surface; moving empty trays from said second conveying surface onto an upstream end of said first conveying surface; and moving empty trays from a downstream end of said first conveying surface onto said second conveying surface.
  • 58. A method for handling trays for use with a flats mail sorter, said method comprising:providing a plurality of tray filling areas and tray filling devices along a mail sorter, said tray filling areas being configured to position trays while said tray filling devices at least partially fill the trays with sorted articles from the mail sorter; providing at least one conveying surface at least partially along said plurality of tray filling areas; conveying empty trays along said at least one conveying surface; moving empty trays from said at least one conveying surface to said tray filling areas; at least partially filling the empty trays at said tray filling areas; moving partially filled trays from said tray filling areas onto said at least one conveying surface; and recycling empty trays along said at least one conveying surface in a generally continuous loop until the empty trays are moved to said tray filling areas.
  • 59. The method of claim 58, wherein an empty tray is recycled along said at least one conveying surface in a generally continuous loop at said tray filling areas.
  • 60. The method of claim 58, wherein said conveying surface comprises at least one of a powered roller conveyor and a continuous belt conveyor.
  • 61. The method of claim 58, wherein prior to moving partially filled trays onto said at least one conveying surface, said method includes determining whether there is a sufficient gap between trays along said conveying surface.
  • 62. A method for handling trays for use with a mail sorter, said method comprising:providing a plurality of tray filling areas and tray filling devices along a mail sorter, said tray filling areas being configured to position trays while said tray filling devices at least partially fill the trays with sorted articles from the mail sorter; providing a first conveying surface along said plurality of tray filling areas; providing a second conveying surface along said plurality of tray filling areas, wherein said first and second conveying surfaces are connected together to define a closed path; conveying empty trays along said first and second conveying surfaces; moving empty trays from said first conveying surface to said tray support areas; at least partially filling the empty trays at said tray filling areas; moving at least partially filled trays from said tray filling areas onto said first conveying surface; and recycling empty trays around said closed path until the empty trays are moved to said tray filling areas.
  • 63. The method of claim 62 further including providing at least one buffer conveyor for temporarily storing, empty trays along said second conveying surface.
  • 64. The method of claim 63 further including inducting empty trays onto said second conveying surface from said at least one buffer conveyor in response to a reduced number of empty trays being conveyed along said second conveying surface.
  • 65. The method of claim 62, wherein the mail sorter comprises a flats mail sorter.
  • 66. A method for handling trays for use with a mail sorter, said method comprising:providing a plurality of tray support areas and tray filling devices along a mail sorter, said tray support areas being configured to position trays while said tray filling devices at least partially fill the trays with sorted articles from the mail sorter; providing a first conveying surface along said plurality of tray support areas; providing a second conveying surface along said plurality of tray support areas; conveying empty trays along said first and second conveying surfaces in a generally continuous loop at said tray support areas; moving empty trays from said first conveying surface to the said support areas; at least partially filling the empty trays at said tray support areas; moving at least partially filled trays from said tray support areas onto said first conveying surface; moving empty trays from a downstream end of said first conveying surface onto said second conveying surface; and moving empty trays from said second conveying surface onto an upstream end of said first conveying surface.
  • 67. The method of claim 66, further including providing a first return device for moving empty trays from said downstream end of said first conveying surface onto said second conveying surface.
  • 68. The method of claim 67 further including providing at least one second return device for moving empty trays from said second conveying surface to said upstream end of said first conveying surface.
  • 69. The method of claim 68, wherein the mail sorter includes two rows of sorter units and said plurality of tray support areas includes two rows of tray support areas positionable along respective rows of sorter units, said method including providing said first and second conveying surfaces along a first row of said rows of tray support areas, and providing third and fourth conveying surfaces along a second row of said rows of tray support areas, a third return device being operable to move empty trays from a downstream end of said third conveying surface onto said fourth conveying surface.
  • 70. The method of claim 69, wherein conveying empty trays in the generally continuous loop at the mail sorter includes:moving empty trays at a downstream end of said second conveying surface at said first row of tray support areas onto an upstream end of said third conveying surface at said second row of tray support areas via one of said at least one second return device; conveying empty trays along said third conveying surface; moving empty trays from said downstream end of said third conveying surface to an upstream end of said fourth conveying surface via said third return device; and conveying empty trays along said fourth conveying surface to a downstream end thereof.
  • 71. The method of claim 70, wherein conveying empty trays in the generally continuous loop at the mail sorter further includes:moving empty trays from said downstream end of said fourth conveying surface at said second row of tray support areas to an upstream end of said first conveying surface at said first row of tray support areas via another one of said at least one second return device; conveying empty trays along said first conveying surface; moving empty trays from a downstream end of said first conveying surface to an upstream end of said second conveying surface via said first return device; and conveying empty trays along said second conveying surface to said downstream end thereof.
  • 72. The method of claim 71, wherein said first conveying surface is positioned generally above said second conveying surface, and said third conveying surface is positioned generally above said fourth conveying surface.
  • 73. The method of claim 72, wherein said at least one second return device comprises an incline conveying surface.
  • 74. The method of claim 72, wherein said first and third return devices comprise vertical tray moving devices.
CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of U.S. Provisional Pat. Applications, Ser. No. 60/148,831, filed Aug. 13, 1999 by G. Burns and D. Olson for DELIVERY POINT SEQUENCING MAIL SORTING SYSTEM WITH FLAT MAIL CAPABILITY; Ser. No. 60/166,079, filed Nov. 17, 1999 by R. Schiesser for LINEAR ACTUATOR; and Ser. No. 60/211,140, filed Jun. 13, 2000 by G. Bums and D. Olson for AUTOMATIC TRAY HANDLING SYSTEM FOR SORTER, which are hereby incorporated in their entireties herein by reference.

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60/211140 Jun 2000 US