Conveyor and logic systems to return, balance, and buffer processed or empty totes

In some embodiments, apparatuses and methods are provided herein useful to automatically balance and buffer the return of empty containers or other totes to a plurality of areas. In some embodiments, a control circuit employs a logic system in which empty totes are directed along primary, secondary, or tertiary paths depending on information gathered from sensors regarding the availability of space for empty totes at a plurality of potential destinations. In this way, the return of empty totes to one or more points of origin may be buffered to balance the number of empty totes in one or more areas.

TECHNICAL FIELD

This invention relates generally to systems and apparatus for conveying crates, boxes, pallets, containers, or other totes, as well as logic systems for determining where the totes are to be delivered and for determining how to automatically convey them to their destination.

BACKGROUND

In warehouses and other storage facilities, large stores, and factories, there are often specified areas for filling boxes, carts, containers, palettes, or other totes for carrying various goods. One example is a “picking area,” in which goods received by the facility are sorted into or onto totes for delivery to another area. These totes are conveyed to a second area, often by an automated system of conveyors, and at the second area unloaded so that the goods may be further processed. For instance, the second area may be a consolidation area, where goods are removed from the tote and consolidated with goods of the same type for storage, use, or display. In such systems, the empty totes are stacked and then manually carried or driven by forklift back to their point of origin. If there are multiple picking areas, one picking area may experience a shortage of empty totes, and workers in that area may request that excess totes be manually gathered from a different picking area. There are no known systems in place for automatically distributing empty totes to one or more filling or picking areas on an as-needed basis so that a baseline number of empty totes is maintained.

U.S. Pat. No. 5,715,660 describes a station with two adjacent vertical conveyors, one for supplying empty containers to the station, and one for removing and unloading filled containers. The device may include sensing circuitry to determine when a container located at the station is full, but the system simply removes full containers and replaces them with empty containers without determining whether to direct empty containers to a different destination when the station is occupied. U.S. Patent Application 2015/0125249 describes a vertical stacking device for stacking empty containers from a plurality of empty container stations, but the disclosed system only sends empty containers to a single destination to be stacked and then removed as a stack. There remains a need for an automated system to efficiently manage and distribute empty totes as needed at one or more points within the system.

DETAILED DESCRIPTION

Generally speaking, and pursuant to various embodiments, systems, apparatuses, and methods are provided herein that are useful to automatically balance and buffer the return of empty totes as needed to either an area in which they are to be filled or to an alternative destination, such as a storage area or alternative filling area. After full totes are conveyed by a conveyor line to a first area from a second area and are emptied at the first area, they are automatically returned to the second area for re-filling if empty totes are needed at that location. If the filling area has reached a specified capacity of empty totes, or in some cases if there is a greater need for totes at a different filling station, the empty totes may be instead diverted by a buffer component from the conveyor line to another filling station. Multiple filling stations and/or multiple emptying stations may be linked in a single system, with any desired ratio of filling stations to emptying stations. Preferably, the system interconnects from two to six filling stations with two to six emptying stations. Each emptying station may be coupled to one or more filling stations, but need not necessarily be directly connected to multiple filling stations. Likewise, each filling station may be coupled to one or more emptying stations, but need not necessarily be directly connected to multiple filling stations. If the system determines that all or some of the filling stations have no immediate need for additional totes, the empty totes may instead be directed to a loop to return the totes to an upstream position, transfer line leading to a different area, tote storage (e.g. a stacking device), or other alternative location. In some embodiments, the system includes a conveyor line connecting a filling area to emptying area, a sensor configured to detect a need for empty totes at the second area, a buffer component coupled to the conveyor line, and a control circuit configured to signal the buffer component to direct the empty totes to the filling area when the sensor detects a need for empty totes at the filling area and to signal the buffer component to direct at least one empty tote to an alternative destination when the sensor does not detect a need for empty totes at the second area.

In another form, methods for distributing empty totes from a first area are provided that include moving empty totes along a conveyor line connecting the first area to a filling area, receiving at a control circuit signals from a sensor configured to detect the presence or absence of a tote at a specified location in the filling area, and communicating a transfer signal from the control circuit to a transfer device when the sensor detects the presence of a tote at the specified location, the transfer signal effective to cause the transfer device to direct empty totes from the conveyor line to a buffer component.

In some embodiments, the systems and methods described herein reduce labor hours and time necessary to balance the numbers of totes. Automation of empty tote return allows throughput to increase without a corresponding increase in labor and other costs for balancing totes across a conveyor system. Further, it offers a system for balancing totes evenly across multiple destinations in a way that is not possible when manually returning totes, and offers dramatically increased speed relative to traditional systems. In some embodiments, the system may return and balance a number of empty totes that would normally require about 5-10 human employees per shift. The speed with which totes are returned may vary, but in some embodiments the system may have the capacity to move about 1,000 totes or more over each transfer point. Limits may be set on the number of totes passing by a single transfer point in a given amount of time, with sensors near transfer points tracking the number of totes passing by and transmitting signals relating to traffic in specified areas in order to cause the system to reduce the speed with which totes are transferred if necessary.

In some embodiments, the totes referenced herein may be any devices or structures for holding or supporting one or more items during conveyance. The term “tote” may refer to, without limitation, a box, crate, basket, container, drum, barrel, cage, tray, pallet, platform, rack, bag, or other device suitable for use in transporting goods. Totes may be of any shape or size suitable for conveyance on the conveyor line. Totes may be open, closed, or partially closed, and may support items thereon, suspend items therefrom, hold items in an interior space, or secure items to its exterior. Totes may be rigid or flexible. Preferably the conveyor lines convey a plurality of the same or similar totes, although different totes may also be used on the same conveyor line in some embodiments.

In one form, the conveyor line linking the first area to the second area may be a belt conveyor, roller conveyor, chain conveyor, or any other known type of conveyor of transport line. The line may include one or more conveyor devices and one or more transfer points. The conveyor may underlie the totes that it conveys, or may be overhead, such as a hook conveyor system. Depending on the relationship between the first area and the second area, the conveyor line may be horizontal, vertical, both horizontal and vertical, and/or an assembly of various horizontal and vertical components.

In some embodiments, the buffer component redirects totes from the empty tote return conveyor line in response to signals from the control circuit. The buffer component may be activated, for instance, when the filling area is no longer in need of empty totes or when another area has a greater need for empty totes. The buffer component may be a transfer device (e.g. right angle transfer device, pop-up device, lift-and-transfer device, roller belt device, tooth belt device, transfer chute, or other mechanism for shifting items to a different conveyor or providing branching paths). In addition, or alternatively, the transfer device may include or lead to a transfer conveyor line, storage area (e.g. dense storage area and/or tote stacking device), or other mechanism for moving totes from the conveyor line to an alternative route or destination.

In some embodiments, the system may utilize one or more sensors to determine if there is a need for empty totes at the second area and/or to determine if there is an excess of totes at the second area or at some point along the conveyor line. One or more sensors may be positioned in or near the area in which totes are filled to determine when totes are present or absent, or even to determine the number of totes present in a location. Sensors may be alternatively, or additionally, positioned at one or more points along the conveyor line to determine the position(s) of totes and/or determine when the conveyor line is substantially full of empty totes. For instance, a plurality of sensors may be placed in spaced apart relationships along then entire conveyor line to determine how many totes are present on the conveyor line. The sensors may be of any type, including an optical sensor, pressure or weight sensor, acoustic sensor, chemical sensor, magnetic sensor, thermal sensor, tripwire, physical switch or lever, or any other device capable of detecting the presence or absence of totes at a given location. A combination of different sensors may also be used. Sensors may be located anywhere that allows them to detect the presence or absence of totes, for instance above, below, or beside conveyors. In some embodiments, sensors may be located below the conveyors, detecting totes through openings between roller conveyors or at joints between belt conveyors. In some embodiments, the sensors may be under-mounted ILTs. In some embodiments, sensors may be placed throughout the system at regular intervals, such as every 12, 24, 36, or 48 inches so that the capacity of any given area can be readily increased or decreased by assigning different sensors as capacity markers. For instance, any one of dozens of sensors proximate the end of a conveyor line may be assigned as the maximum capacity marker at any given point in time, with a second sensor half-way to the end then indicating 50% capacity, and a third sensor between the first and second sensors indicating 75% capacity.

In some embodiments, the sensor is configured to directly or indirectly signal information regarding the presence and/or absence of totes at a given location to a control circuit. The control circuit may be of any processor-based or electronic computer-type device known in the art for processing information and receiving signals and transmitting control signals in response to the received signals.

The term control circuit refers broadly to any microcontroller, computer, or processor-based device with processor, memory, and programmable input/output peripherals, which is generally designed to govern the operation of other components and devices. It is further understood to include common accompanying accessory devices. These architectural options are well known and understood in the art and require no further description here. The control circuit may be configured (for example, by using corresponding programming stored in a memory as will be well understood by those skilled in the art) to carry out one or more of the steps, actions, and/or functions described herein. Generally, the control circuit and/or electronic components of a related interface device can include fixed-purpose hard-wired platforms or can comprise a partially or wholly programmable platform. These architectural options are well known and understood in the art and require no further description here. The user interface unit and/or control circuit can be configured (for example, by using corresponding programming as will be well understood by those skilled in the art) to carry out one or more of the steps, actions, and/or functions described herein. In some implementations, the control circuit and a computer memory may be integrated together, such as in a microcontroller, application specification integrated circuit, field programmable gate array or other such device, or may be separate devices coupled together.

The control circuit may comprise multiple subsystems. For instance, in some embodiments local control mechanisms may govern decisions at each buffer point and/or identify errors or jams in the system, with an overall control mechanism communicating with and coordinating each local control mechanism. In some embodiments individual local control systems may be shut off in order to repair or address other problems in a given area, and the overall control system may bypass that area without shutting down other local control systems.

In some embodiments, the empty tote return, buffer, and transfer system automatically transfers and balances a quantity of totes between, for instance, a picking area, consolidation, area, and storage area. The system may include transport from consolidation that transports empty totes to a decision point where the tote can be directed to a picking area, a transfer line, or a storage area. The transfer line may serve as both a tote buffer and a transfer mechanism between the transport conveyance from consolidation, storage area, and transport conveyance to the picking area. The storage area may function as a dense storage mechanism for empty totes, and may be comprised of a series of conveyor systems, one or many tote stackers, or other mechanisms that facilitate the storage of totes. A transport conveyance to the picking area may transport empty totes from transfer lines, storage, or directly from consolidation. Empty totes may be buffered for picking associates and pass through each destination in the picking area.

In some embodiments, a logic or control system directs the movement and flow of totes within the system, and may comprise a control circuit coupled to one or more sensors configured to detect the presence or absence of totes. The control system sends signals instructing transfer mechanisms to shift totes to specific conveyances in response to signals received from the one or more sensors. The system is designed to be flexible, and permits totes processed at any number of processing stations to be automatically transferred depending on the status of other totes within the system. Multiple inputs and outputs of the system may be balanced through the use of one or more transfer and/or buffering components. Independent buffer components may be configured to work in unison in accordance with the systems logic, so that any conveyor in the system can become an input into one or more storage units or one of multiple outputs. The control system may orchestrate movement between physical elements of the systems based on detected information and built-in logic to ensure that there is a balanced number of empty totes on each line. The empty tote management system may have physical connections between all conveyor lines so that totes from any input may be directed to any output, allowing balancing of totes across each and every line. When one area does not contain a minimum threshold of empty totes, the system logic may cause empty totes to be delivered to that area. Similarly, when one area contains totes in excess of a maximum threshold, system logic may direct totes away from that area. If all destinations are above the minimum threshold of empty totes, additional empty totes may be either directed on the most direct path for their default output area or, alternatively, to a storage area, depending on the system logic implemented.

Referring toFIG. 1, a warehouse distribution system is shown in which two picking areas1and2at which items are picked and placed into totes are connected to respective consolidation areas3and4by parallel conveyor lines5and7. While the system shown inFIG. 1depicts a 1:1 ratio of picking areas to consolidation areas, it should be noted that the number of picking areas need not mirror the number of consolidation areas, and any number of picking areas and consolidation areas may be provided with each picking area and consolidation area connected to any number of other areas. Totes filled with picked items are conveyed from picking area1to consolidation area3along conveyor line5, and from picking area2to consolidation area4along conveyor line7. Solid arrows show the direction of transport for full totes. When totes are emptied at consolidation areas3and4, the empty totes are returned to the picking areas via conveyor lines6and8, respectively. Outline arrows show the direction of transport for empty totes along conveyor lines6and8. Sensors13and15detect whether there is available space for additional empty totes at picking areas1and2, respectively. When sensor13detects that there is no longer a need for additional totes at picking area1, for instance by detecting that a tote is physically present at the entrance to picking area1, sensor13sends a signal to a control circuit17to activate a buffer component to divert additional totes away from picking area1. Sensor13may be coupled to the control circuit17by a hard-wire connection, wireless connection, or any other manner known in the art. Alternatively, the buffer component may be activated by default and de-activated when the sensor13detects that there is space available at picking line1for additional empty totes.

The buffer component shown inFIG. 1includes a transfer line9connecting return conveyor line6to return conveyor line8, and also leading to an alternative destination12and a dense tote storage area11. Totes may be shifted to transfer line9by any known device, including various types of pop-up transfer devices and right-angle transfer devices. Alternative destination12may comprise an unlimited number of components providing an unlimited number of alternative destinations for the empty totes, and may be, for instance, a third picking area or one or more additional return conveyor lines connecting additional picking areas to additional consolidation areas.

InFIG. 1, when sensor13indicates that there is no need for empty totes at picking area1(e.g. when picking area1is full), control circuit17will divert totes being delivered along return conveyor6to transfer conveyor9. If sensor15indicates that there is a need for empty totes at picking area2, the control circuit17may be programmed to signal a transfer device to shift totes from transfer line9to return conveyor line8so that empty totes are directed to picking area2rather than picking area1. If and when sensor15indicates that empty totes are no longer needed at picking area2, totes will be allowed continue along transfer line9toward an alternative destination12unless sensor13alerts the control circuit to a need for empty totes detected at picking area1.

One or more sensors positioned to detect a need for empty totes at alternative destination12may be configured to signal the control circuit when empty totes are no longer needed at alternative destination12, and the control circuit will accordingly redirect empty totes from transfer line9to a dense tote storage area11via a transfer device, such as a pop-up transfer device or right-angle transfer device. Totes may be stacked or nested at the dense storage area, for instance in a magazine-like chamber, and may be reintroduced to return line6or8via return transfer line10. Transfer lines9and10optionally may be omitted so that transfer devices shift empty totes directly to dense tote storage area11.

In a similar process, empty totes returning to picking area2along return conveyor8may be redirected to picking area1, alternative destination12, or storage area11depending on the signals transmitted by sensor15and a sensor for alternative destination12, which are configured to detect the need for totes at those locations.

FIG. 2is a basic logic diagram illustrating steps of one embodiment of a method of managing empty totes. The embodiments of the method ofFIG. 2may be performed by the components of the system100ofFIG. 1or other systems. The illustrated method begins with a user or automated device emptying a tote at an emptying area and placing the empty tote on a return conveyor (step18). A control circuit (e.g. control circuit17inFIG. 1or a suitable control circuit of another system) coupled to sensors in various locations sequentially determines the availability of prioritized paths to determine the route to be taken by the empty tote. First, the control circuit determines whether a primary path is available (Step18a) by detecting the presence or absence of totes at a given location. If the primary path is available, the control circuit will send signals causing the empty totes to be directed along the primary path. Assuming the primary path is not available, the control circuit determines if a secondary path is available (Step18b) by detecting the presence or absence of totes at a given location along the secondary path. If the secondary path is available, the control circuit will send signals causing the empty totes to be directed along the secondary path. If the secondary path is unavailable, the control circuit will determine if additional paths are available. This process may be repeated for N number of alternative paths (Step18c) until it is determined that paths1to N are unavailable. When the Nth path is unavailable, the control circuit directs totes to a dense storage where the totes are stacked for later use (Step19). The control circuit continues to monitor pathways1through N, and when a pathway becomes available will direct totes from the dense storage area to the available pathway. For instance,FIG. 2shows the control circuit returning to Step18aafter storing a tote in the dense storage area (Step19). However, it should be noted that the control circuit may alternatively be configured to return directly to Step18bor18cafter Step19, and need not re-assess the availability of all available return paths.

FIG. 3shows an example of a default state of a partial empty tote management, buffering, and balancing system where a first conveyor line6returns empty totes to picking area1from consolidation area3and conveyor line8returns empty totes to picking area2from consolidation area4. Certain details shown inFIG. 1are omitted from this figure for purposes of clarity. In the default state, totes are conveyed directly from consolidation area3to picking area1and from consolidation area4to picking area2. The flow of empty totes may be buffered by one or more buffer components. For instance, transfer devices20and21are connected by transfer conveyor10, and may be instructed by the control circuit to redirect totes from one conveyor line to the other. Similarly, downstream transfer devices22and23may redirect totes between lines along transfer conveyor9. Transfer conveyors9and10may be unidirectional or may be able to change direction based on the desired path of totes, and may be coupled with additional conveyor lines to increase the variety of potential routes available.

As shown inFIG. 3, sensors13and15indicate that picking areas1and2, respectively, have room for additional empty totes. As a result, empty totes are routed from consolidation areas3and4along direct paths, as indicated by outline block arrows. Transfer lines9and10are not active in this state.

FIG. 4depicts an alternative state of the system shown inFIG. 3, in which sensor15indicates that picking area2is full.FIG. 15sends a signal to the control circuit indicating that picking area2is no longer in need of empty totes. As a result, the control circuit assesses whether a secondary path is available. In this case, the control circuit determines whether picking area1is in need of empty totes. Sensor13located at picking area1indicates that the picking area is not full, and as a result the control circuit directs transfer device20to direct empty totes from consolidation area4along transfer conveyor10, as shown by arrows, and they are merged by transfer device21with totes from consolidation area3along conveyor line6. Totes from consolidation area3continue on a path straight through transfer devices21and22to picking area1as long as sensor13indicates that picking area1is not full. When sensor15indicates that picking area2is no longer full, the control circuit will instruct transfer device20to begin once again directing totes from consolidation area4along conveyor line8to picking area2.

InFIG. 5, sensors13and15indicate that both of picking areas1and2have reached a maximum capacity for empty totes. In response, the control circuit directs transfer devices22and23to direct totes from both of lines6and8along transfer conveyor9. If the control circuit receives signals indicating that an alternative destination12is available, totes from consolidation areas3and4will be directed through transfer device24to the alternative destination12, which may be one or more picking areas, one or more additional conveyor lines, or another area in which empty totes may be utilized or directed to different areas. If and when the control circuit detects that the alternative destination12is no longer available, as inFIG. 6, the control circuit will instruct transfer device24to instead direct totes travelling along transfer conveyor9to a dense tote storage11, where they may be stored until sensors indicate a need for empty totes at one or more destinations.

FIG. 7shows the empty tote management system ofFIG. 3in a state in which picking areas1and2need empty totes, but conveyor line6is full as indicated by sensor14. In addition, additional totes are provided to conveyor line8at a point25downstream from transfer device20. In response to the influx of totes at point25, the control circuit instructs transfer device to alter the primary path of totes from consolidation area4so that they are conveyed along transfer line10to conveyor line6and merged with the stream of totes conveyed from consolidation area3, as shown by arrows. When sensor14indicates that conveyor line6is full, the control circuit may instead instruct transfer device20to redirect totes from consolidation area4straight through along line8, the former default path. If sensor16begins to indicate that line8is backed up with empty totes, transfer device23may be directed to clear line8by temporarily redirecting some or all totes along transfer line9, unless sensor14indicates that line6has cleared, in which case the control circuit will signal transfer device20to again begin directing empty totes from consolidation area4to conveyor line6via transfer line10.

InFIG. 8, sensor15indicates that picking area2is full, causing transfer device20to direct totes from consolidation area4along a secondary path to conveyor line6, as shown by arrows with solid outline. However, when sensor14indicates that conveyor line6is full, the control circuit will begin directing totes from consolidation4along a tertiary path straight through transfer device20and right at transfer device23onto transfer line9. As shown in other figures, the management system may be configured to direct totes to alternative destination12unless unavailable, in which case transfer device24will stack totes in dense storage11.

In all examples above, different preferences and priorities may be given to the described routes. For instance, inFIG. 8the secondary path for totes from consolidation area4may be along transfer line9rather than line10, irrespective of whether conveyor line6is full. Similarly, totes travelling along transfer line9may be preferentially directed to dense storage11unless full, in which case they will be directed to alternative destination12. The logic system may be modified and adapted as needed for any particular configuration of empty tote conveyor lines.

In some embodiments, an apparatus and a corresponding method performed by the apparatus, comprises multiple conveyor lines connecting multiple filling and emptying areas; a plurality of sensors configured to detect need for empty totes at the filling areas; one or more buffer components coupled to the conveyor lines; and a control circuit in communication with the sensors and the buffer components, the control circuit configured for output signaling to direct the empty totes according to detected need. The buffer component may comprise a buffer conveyor line connected to one or more conveyor line at one or more transfer points, a dense tote storage area coupled to the conveyor line, or other mechanism. The plurality of sensors may be the same or different, and in one example may be optical sensors that detects the presence or absence of a tote at specified locations.

In some embodiments, a method carried out by the described systems is shown inFIG. 9. The process starts with empty totes being moved along a conveyor line that connects a first area to a filling area where the empty totes are to be filled (Step26). A control circuit, such as the control circuit17shown inFIG. 1or any other suitable control circuit, receives signals from a sensor located in the filling area (Step27), the sensor being configured to detect the presence or absence of a tote at a specified location in the filling area. The sensor may alternatively be positioned outside the filling area and/or detect the presence or absence of a tote at a specified location along a path to the filling area. A plurality of sensors may also be positioned to detect totes at multiple locations. In response to signals received from the sensor, the control circuit communicates a transfer signal to a transfer device when the sensor detects the presence of a tote at the specified location, causing a transfer device to direct empty totes to a buffer component (Step28). Optionally, the buffer component may direct empty totes to a second conveyor line (Step29). Alternatively, the totes may be directed to a dense storage area or other area. Once empty totes are directed along a second conveyor line, the control circuit may optionally receive signals form a second sensor or group of sensors configured to detect the presence or absence of totes at a specified location or multiple specified locations in or leading to a second filling area connected to the second conveyor line (Step30). Optionally, the control circuit may also communicate a signal to divert empty totes to a dense storage area if the second sensor or group of sensors detect totes at the one or more specified locations in or leading to the second filling area (Step31).

FIG. 10is an overhead schematic diagram of one particular embodiment of the present invention comprising a system40of conveyors capable of moving empty totes from consolidation areas to picking areas. The system40is associated with a series of conveyors that move full totes from the picking areas to the consolidation areas, and is configured so that the system40is located at a vertical level that is different than the vertical level of the system of conveyors for full totes (i.e. above or below the conveyor lines for full totes). Conveyors are represented by lines, while transfer points are indicated by squares and sensors are indicated by dots. Conveyor lines41,42, and43are generally parallel and run continuously in the same direction. A transverse buffer line46connects conveyor lines42and43at a pair of pop-up right angle transfer devices to allow totes to be transferred in a single direction from conveyor line42to conveyor line43. The buffer line46connects to conveyor line43at a ramp entrance to transfer line51, so that totes on conveyor line43that arrive at buffer line46may continue along conveyor line43or be re-directed to transfer line51. Totes moving along conveyor line42that reach buffer line46may continue along conveyor line42or be re-directed to either conveyor line43or transfer line51depending on the state of the two transfer devices associated with buffer line46. A sensor67is positioned along buffer line46in order to alert a control circuit if buffer line46becomes jammed. Downstream of the transfer line, buffer line47connects conveyor lines41,42, and43, running in a single direction (toward the top ofFIG. 10) with pop-up right angle transfer devices that allow totes from conveyor line43to shift to conveyor lines41or42. Buffer line48runs parallel to buffer line47and in the opposite direction, allowing transfer of totes from conveyor line41to conveyor line42. Associated sensors alert the system when the buffer line is full and should not receive additional totes. A series of sensor devices49detect the presence or absence of totes near the picking areas associated with conveyor lines41,42, and43, and are capable of sending signals to the control circuit indicating that totes should be directed to or away from a particular conveyor line based on need for empty totes at the picking area. Each line may have a plurality of sensors at the picking area, extending along a distance at the end of the conveyor that defines a maximum capacity for totes, with individual sensors spaced in order to alert the system when specific percentages of the maximum capacity have been reached.

On the opposite side of the system40, conveyor lines44and45run generally parallel to lines41,42, and43, and connect two additional consolidation areas and two additional picking areas. Buffer line66connects conveyor lines44and45, and right-angle pop-up transfer devices at the connection points allow totes to be moved from conveyor line45to conveyor line44or transfer line52. Buffer line64likewise allows movement of totes in the opposite direction, from conveyor line44to conveyor line45. Sensors65detect the presence or absence of totes near the picking areas associated with conveyor lines45, and are capable of sending signals to the control circuit indicating that totes should be directed to or away from a particular conveyor line based on need for empty totes at the picking area.

Connecting the two distinct groups of conveyor lines is the transfer device comprising transfer lines51and52. The lines cross one another at a cross-over point53where transfer line51passes over transfer line52so that each line can receive totes from at least one conveyor line and feed into at least one other conveyor line in a manner that minimizes disruption along those lines. For instance, transfer line51has a curved entrance ramp at its beginning, where it connects to conveyor line43, and at its end has a curved ramp merging with conveyor line43. Alternatively, totes approaching the end of transfer line51may be redirected at transfer point62to conveyor line45via right angle pop-up transfer device63. Similarly, totes from conveyor line44may be transferred along transfer line52to conveyor line43along ramp54, or conveyor line42via transfer device55. The transfer device50, in combination with the various buffer lines, allow totes from the five consolidation areas associated with the five conveyor lines41,42,43,44, and45to be redistributed to other picking areas as needed to balance the availability of totes. When all of the picking areas have reached a specified capacity of totes, totes may be redirected to dense storage areas associated with the transfer device50. Buffer line56connects transfer lines51and52near the first group of conveyor lines and leads to a bi-directional stacking device57that can either stack totes vertically for later use or send totes through a loop58which provides excess tote capacity while still leaving them readily available to re-enter one of the conveyor lines. Bi-directional stacking device57may receive and distribute totes from either of two directions. The system logic may be designed so that totes are first diverted to the loop structure58, passing through the stacking device57, and are only stacked in the stacking unit57when sensors associated with the loop58indicate that the loop is at or near its maximum capacity. Similarly, buffer line59connects transfer lines51and52near the second group of conveyor lines and allows totes to be diverted to bi-directional stacking device60and/or loop61.