Patent Publication Number: US-2023162150-A1

Title: Storage and retrieval system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. non-provisional patent application Ser. No. 16/950,383, filed on Nov. 17, 2020, (now U.S. Pat. No. 11,562,321),which is a continuation of U.S. non-provisonal patent application Ser. No. 16/718,918, filed on Dec. 18, 2019, (now U.S. Pat. No. 10,839,347), which is a continuation of U.S. non-provisional patent application Ser. No. 16/162,247, filed on Oct. 16, 2018, (now U.S. Pat. No. 10,521,767), which is a continuation of U.S. non-provisional patent application Ser. No. 14/997,925, filed on Jan. 18, 2016, (now U.S. Pat. No. 10,102,496), which claims priority from and the benefit of U.S. Provisional Patent Application No. 62/104,531 filed on Jan. 16, 2015, the disclosures of which are incorporated by reference herein in their entireties. 
     This application is also related to U.S. patent application Ser. No. 15/890,088 filed on Feb. 6, 2018, which is a continuation of U.S. patent application Ser. No. 14/966,978, filed on Dec. 11, 2015, (now U.S. Pat. No. 9,884,719 issued on Feb. 6, 2018); U.S. patent application Ser. No. 14/997,892, filed on Jan. 18, 2016; U.S. patent application Ser. No. 14/997,902, filed on Jan. 18, 2016; U.S. patent application Ser. No. 15/848,809, filed on Dec. 20, 2017, which is a continuation of U.S. patent application Ser. No. 14/997,920, filed on Jan. 18, 2016 (now U.S. Pat. No. 9,856,083 issued on Jan. 2, 2018); and U.S. Provisional Patent Application No. 62/107,135, filed on Jan. 23, 2015, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     1. Field 
     The exemplary embodiments generally relate to material handling systems and, more particularly, to transport and storage of items within the material handling system. 
     2. Brief Description of Related Developments 
     Multilevel storage and retrieval systems may be used in warehouses for the storage and retrieval of goods. Generally the transportation of goods into and out of the storage structure is done with lifts for transfer to a vehicle on a storage level, vehicles travelling up ramps to a predetermined storage level, or with vehicles that include lifts traveling along guide ways. Goods stored within the storage and retrieval system are generally stored in storage spaces on each storage level such that a transport vehicle disposed on that level has access to one level of storage spaces. Generally, the lifts that transfer items to and from the storage spaces carry the vehicles between different storage levels, are incorporated into the vehicles (such as with a gantry crane) or have a paternoster configuration where the lift payload shelves continually circulate around a frame at a predetermined rate. 
     Generally sequencing of items picked from storage is performed by the vehicles picking the items or by a dedicated sorter that sorts the items during an outbound flow after being transported by the gantry crane or paternoster lift. The sorting of outbound items in this manner may result in the lifts performing multiple lift strokes to pick the items needed for a load-out or additional sorting steps thereby decreasing throughput of the storage and retrieval system. 
     It would be advantageous to increase a rate of item transfer to and from the different storage levels within a storage and retrieval system where items of a load-out are sorted at a lift interface and picked with a common lift stroke and where an order of sorted items at the lift interface is matched to a load stream of a common load, lift interface and/or lift. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of the disclosed embodiment are explained in the following description, taken in connection with the accompanying drawings, wherein: 
         FIG.  1    is a schematic illustration of an automated storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIG.  1 A  is a schematic illustration of a portion of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIG.  1 B  is a schematic illustration of a portion of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIG.  1 C  is a schematic illustration of a portion of the automated storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIG.  2    is a schematic illustration of a mixed pallet load formed by the automated storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIGS.  3 A and  3 B  are schematic illustrations of portions of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIGS.  4 A and  4 B  are schematic illustrations of portions of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIGS.  5 A,  5 B,  5 C,  5 D and  5 E  are schematic illustrations of portions of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIG.  6    is a schematic illustration of a portion of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIG.  6 A  is a flow diagram in accordance with aspects of the disclosed embodiment; 
         FIGS.  7 ,  7 A- 7 E  are schematic illustrations of a portion of the storage and retrieval system in accordance with aspects of the disclosed embodiment; 
         FIGS.  8 - 13    are flow diagrams in accordance with aspects of the disclosed embodiment; 
         FIG.  14    is a schematic illustration of an operator station of the storage and retrieval system in accordance with aspects of the disclosed embodiment; and 
         FIG.  15    is an exemplary flow diagram in accordance with aspects of the disclosed embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a schematic illustration of an automated storage and retrieval system  100  in accordance with aspects of the disclosed embodiment. Although the aspects of the disclosed embodiment will be described with reference to the drawings, it should be understood that the aspects of the disclosed embodiment can be embodied in many forms. In addition, any suitable size, shape or type of elements or materials could be used. 
     In accordance with aspects of the disclosed embodiment the automated storage and retrieval system  100  may operate in a retail distribution center or warehouse to, for example, fulfill orders received from retail stores for case units such as those described in U.S. patent application Ser. No. 13/326,674 filed on Dec. 15, 2011, the disclosure of which is incorporated by reference herein in its entirety. For example, the case units are cases or units of goods not stored in trays, on totes or on pallets (e.g. uncontained). In other examples, the case units are cases or units of goods that are contained in any suitable manner such as in trays, on totes or on pallets. In still other examples, the case units are a combination of uncontained and contained items. It is noted that the case units, for example, include cased units of goods (e.g. case of soup cans, boxes of cereal, etc.) or individual goods that are adapted to be taken off of or placed on a pallet. In accordance with the aspects of the disclosed embodiment, shipping cases for case units (e.g. cartons, barrels, boxes, crates, jugs, or any other suitable device for holding case units) may have variable sizes and may be used to hold case units in shipping and may be configured so they are capable of being palletized for shipping. It is noted that when, for example, bundles or pallets of case units arrive at the storage and retrieval system the content of each pallet may be uniform (e.g. each pallet holds a predetermined number of the same item—one pallet holds soup and another pallet holds cereal) and as pallets leave the storage and retrieval system in a load-out the pallets may contain any suitable number and combination of different case units (e.g. a mixed pallet where each mixed pallet holds different types of case units—a pallet holds a combination of soup and cereal) that are provided to, for example the palletizer in a sorted arrangement for forming the mixed pallet. In the embodiments the storage and retrieval system described herein may be applied to any environment in which case units are stored and retrieved. 
     Also referring to  FIG.  2   , as noted above, when, for example, incoming bundles or pallets (e.g. from manufacturers or suppliers of case units arrive at the storage and retrieval system in a load-in for replenishment of the automated storage and retrieval system  100 , the content of each pallet may be uniform (e.g. each pallet holds a predetermined number of the same item—one pallet holds soup and another pallet holds cereal). As may be realized, the cases of such pallet load may be substantially similar or in other words, homogenous cases (e.g. similar dimensions), and may have the same SKU (otherwise, as noted before the pallets may be “rainbow” pallets having layers formed of homogeneous cases). As pallets PAL leave the storage and retrieval system  100  in a load-out, with cases filling replenishment orders, the pallets PAL may contain any suitable number and combination of different case units CU (e.g. each pallet may hold different types of case units—a pallet holds a combination of canned soup, cereal, beverage packs, cosmetics and household cleaners). The cases combined onto a single pallet may have different dimensions and/or different SKU&#39;s. In the exemplary embodiment, referring also to  FIG.  1 B , the storage and retrieval system  100  is configured to generally include an in-feed section (including one or more input stations  160 IN), a storage and sortation section  100 SS (including, in one aspect, multilevel case storage  170 , horizontal case transport  171 , case buffering and vertical case transport  173 ) and an output section  100 US (including one or more output stations  160 UT) as will be described in greater detail below. In other aspects one or more of the case buffering  172  and vertical case transport  173  are included in the output section  100 US while in still other aspects the case buffering  172  and vertical case transport  173  are common to both the storage and sortation section  100 SS and the output section  100 US. As may be realized, in one aspect of the disclosed embodiment, the system  100  operating for example as a retail distribution center may serve to receive uniform pallet loads of cases, breakdown the pallet goods or disassociate the cases from the uniform pallet loads into independent case units handled individually by the system, retrieve and sort the different cases sought by each order into corresponding groups, and transport and assemble the corresponding groups of cases into what may be referred to as mixed case pallet loads MPL. As may also be realized, as illustrated in  FIG.  14   , in one aspect of the disclosed embodiment the system  100  operating for example as a retail distribution center may serve to receive uniform pallet loads of cases, breakdown the pallet goods or disassociate the cases from the uniform pallet loads into independent case units handled individually by the system, retrieve and sort the different cases sought by each order into corresponding groups, and transport and sequence the corresponding groups of cases (in the manner described herein) at an operator station  160 EP where items are picked from the different case units CU, and/or the different case units CU themselves, are placed in one or more bag(s), tote(s) or other suitable container(s) TOT by an operator  1500 , or any suitable automation, in a predetermined order sequence of picked items according to, for example, an order, fulfilling one or more customer orders, in which the case units CU are sequenced at the operator station  160 EPin accordance with the predetermined order sequence, noting that the sequencing of the case units CU as described herein effects the sequencing of the case units CU at the operator station  160 EP. 
     The in-feed section may generally be capable of resolving the uniform pallet loads to individual cases, and transporting the cases via suitable transport, for input to the storage and sortation section. The storage and sortation section in turn may receive individual cases, store them in a storage area and retrieve desired cases individually in accordance with commands generated in accordance to orders entered into a warehouse management system for sequenced  174  transport to the output section  100 US. The sorting and grouping of cases according to order (e.g. an order or load out sequence) may be performed in whole or in part by either the storage and sortation section  100 SS or the output section  100 US, or both, the boundary between being one of convenience for the description and the sorting and grouping being capable of being performed any number of ways. For example, as noted above, while the case buffering  172  and vertical case transport  173  are shown in  FIG.  1 B  as being included in the storage and sortation section  100 SS, in other aspects one or more of the case buffering  172  and vertical case transport  173  are included in the output section  100 US and/or are common to both the storage and sortation section  100 SS and the output section  100 US. The intended result is that the output section assembles the appropriate group of ordered cases, that may be different in SKU, dimensions, etc. into, in one aspect, mixed case pallet loads in the manner described in, for example, U.S. patent application Ser. No. 13/654,293 filed on Oct. 17, 2012 (now U.S. Pat. No. 8,965,559), the disclosure of which is incorporated herein by reference in its entirety, while in other aspects the output section assembles the appropriate group of ordered case units, that may be different in SKU, dimensions, etc. into bags, totes or other suitable containers according to the predetermined order sequence of picked items at the operator station  160 E (such as to e.g., fill a customer order). 
     In one aspect of the exemplary embodiment, the output section  100 US generates the pallet load in what may be referred to as a structured architecture of mixed case stacks. The structured architecture of the pallet load may be characterized as having several flat case layers L 121 -L 125 , L 12 T, at least one of which is formed of non-intersecting, free-standing and stable stacks of multiple mixed cases. The mixed case stacks of the given layer have substantially the same height, to form as may be realized substantially flat top and bottom surfaces of the given layer, and may be sufficient in number to cover the pallet area, or a desired portion of the pallet area. Overlaying layer(s) may be orientated so that corresponding cases of the layer(s) bridge between the stacks of the supporting layer. Thus, stabilizing the stacks and correspondingly the interfacing layer(s) of the pallet load. In defining the pallet load into a structured layer architecture, the coupled 3-D pallet load solution is resolved into two parts that may be saved separately, a vertical (1-D) part resolving the load into layers, and a horizontal (2-D) part of efficiently distributing stacks of equal height to fill out the pallet height of each layer. In other aspects the load fill of mixed cases may be configured in any other suitable ordered sequence and may be loaded on or in any suitable transport device such as, for example, a bag, tote, shopping carriage, a truck or other suitable container fill without palletization. As will be described below, the storage and retrieval system outputs case units to the output section so that the two parts of the 3-D pallet load solution are resolved, while in other aspects the storage and retrieval system outputs case units to the output section according to a sequence for filling non-palletized item picking sequence orders at the operator station  160 EP. The term load fill or container fill as used herein refers to case units that are delivered to either a pallet load fill section/cell (such as for the creation of a mixed pallet load MPL) or an itemized load fill section/cell as described with respect to  FIG.  14    where both the pallet load fill section/cell and the itemized load fill section/cell are referred to generally as load fill section/station or cell. 
     In accordance with aspects of the disclosed embodiment, referring again to  FIG.  1   , the automated storage and retrieval system  100  includes input stations  160 IN (which include depalletizers  160 PA, operator stations  160 EP and/or conveyors  160 CA for transporting items to lift modules for entry into storage) and output stations  160 UT (which include palletizers  160 PB and/or conveyors  160 CB for transporting case units from lift modules for removal from storage), input and output vertical lift modules  150 A,  150 B (generally referred to as lift modules  150 —it is noted that while input and output lift modules are shown, a single lift module may be used to both input and remove case units from the storage structure), a storage structure  130 , and a number of autonomous transport vehicles  110  (referred to herein as “bots”). As used herein at least the lift modules  150 , storage structure  130  and bots  110  may be collectively referred to herein as the storage and sortation section noted above. It is also noted that the depalletizers  160 PA may be configured to remove case units from pallets so that the input station  160 IN can transport the items to the lift modules  150  for input into the storage structure  130 . The palletizers  160 PB may be configured to place items removed from the storage structure  130  on pallets PAL ( FIG.  2   ) for shipping. 
     Also referring to  FIG.  3 A , the storage structure  130  may include multiple storage rack modules RM, configured in a three dimensional array RMA, that are accessible by storage or deck levels  130 L. Each storage level  130 L includes storage spaces  130 S formed by the rack modules RM where the rack modules include shelves that are disposed along storage or picking aisles  130 A which, e.g., extend linearly through the rack module array RMA and provide access to the storage spaces  130 S and transfer deck(s)  130 B over which the bots  110  travel on a respective storage level  130 L for transferring case units between any of the storage spaces  130 S of the storage structure  130  (e.g. on the level which the bot  110  is located) and any of the lift modules  150  (e.g. each of the bots  110  has access to each storage space  130 S on a respective level and each lift module  150  on a respective storage level  130 L). The transfer decks  130 B are arranged/arrayed at different levels and defining multilevel decks (corresponding to each level  130 L of the storage and retrieval system) that may be stacked one over the other or horizontally offset, such as having one transfer deck  130 B at one end or side RMAE 1  of the storage rack array RMA or at several ends or sides RMAE 1 , RMAE 2  of the storage rack array RMA as described in, for example, U.S. patent application Ser. No. 13/326,674 filed on Dec. 15, 2011, the disclosure of which is incorporated herein by reference in its entirety. 
     The transfer decks  130 B are substantially open and configured for the undeterministic traversal of bots  110  across and along the transfer decks  130 B. As may be realized, the transfer deck(s)  130 B at each storage level  130 L communicate with each of the picking aisles  130 A on the respective storage level  130 L. Bots  110  bi-directionally traverse between the transfer deck(s)  130 B and picking aisles  130 A on each respective storage level  130 L to access the storage spaces  130 S disposed in the rack shelves alongside each of the picking aisles  130 A (e.g. bots  110  may access storage spaces  130 S distributed on both sides of each aisle such that the bot  110  may have a different facing when traversing each picking aisle  130 A, for example, referring to  FIG.  6   , drive wheels  202  leading a direction of travel or drive wheels trailing a direction of travel). As noted above, the transfer deck(s)  130 B also provide bot  110  access to each of the lifts  150  on the respective storage level  130 L where the lifts  150  feed and remove case units to and/or from each storage level  130 L and where the bots  110  effect case unit transfer between the lifts  150  and the storage spaces  130 S. Each storage level  130 L may also include charging stations  130 C for charging an on-board power supply of the bots  110  on that storage level  130 L such as described in, for example, U.S. patent application Ser. No. 14/209,086 filed on Mar. 13, 2014 and Ser. No. 13/326,823 filed on Dec. 15, 2011 (now U.S. Pat. No. 9,082,112), the disclosures of which are incorporated herein by reference in their entireties. 
     The bots  110  may be any suitable independently operable autonomous transport vehicles that carry/hold and transfer case units/pickfaces throughout the storage and retrieval system  100 . In one aspect the bots  110  are automated, independent (e.g. free riding) autonomous transport vehicles. Suitable examples of bots can be found in, for exemplary purposes only, U.S. patent application Ser. No. 13/326,674 filed on Dec. 15, 2011; U.S. patent application Ser. No. 12/757,312 filed on Apr. 9, 2010, (now U.S. Pat. No. 8,425,173); U.S. patent application Ser. No. 13/326,423 filed on Dec. 15, 2011; U.S. patent application Ser. No. 13/326,447 filed on Dec. 15, 2011, (now U.S. Pat. No. 8,965,619); U.S. patent application Ser. No. 13/326,505 Dec. 15, 2011, (now U.S. Pat. No. 8,696,010); U.S. patent application Ser. No. 13/327,040 filed on Dec. 15, 2011, (now U.S. Pat. No. 9,187,244); U.S. patent application Ser. No. 13/326,952 filed on Dec. 15, 2011; U.S. patent application Ser. No. 13/326,993 filed on Dec. 15, 2011; U.S. patent application Ser. No. 14/486,008 filed on Sep. 15, 2014; and U.S. provisional Patent Application No. 62/107,135 filed on Jan. 23, 2015, the disclosures of which are incorporated by reference herein in their entireties. The bots  110  (described in greater detail below) may be configured to place case units, such as the above described retail merchandise, into picking stock in the one or more levels of the storage structure  130  and then selectively retrieve ordered case units. 
     The bots  110 , lift modules  150  and other suitable features of the storage and retrieval system  100  are controlled in any suitable manner such as by, for example, one or more central system control computers (e.g. control server)  120  through, for example, any suitable network  180 . In one aspect the network  180  is a wired network, a wireless network or a combination of wireless and wired networks using any suitable type and/or number of communication protocols. In one aspect, the control server  120  includes a collection of substantially concurrently running programs (e.g. system management software) for substantially automatic control of the automated storage and retrieval system  100 . The collection of substantially concurrently running programs, for example, being configured to manage the storage and retrieval system  100  including, for exemplary purposes only, controlling, scheduling, and monitoring the activities of all active system components, managing inventory (e.g. which case units are input and removed, the order in which the cases are removed and where the case units are stored) and pickfaces (e.g. one or more case units that are movable as a unit and handled as a unit by components of the storage and retrieval system), and interfacing with a warehouse management system  2500 . The control server  120  may, in one aspect, be configured to control the features of the storage and retrieval system in the manner described herein. For simplicity and ease of explanation the term “case unit(s)” is generally used herein for referring to both individual case units and pickfaces (formed of multiple case units). 
     Referring also to  FIGS.  1  and  1 A  the rack module array RMA of the storage structure  130  includes vertical support members  1212  and horizontal support members  1200  that define a high density automated storage array such as described in, for example, U.S. patent application Ser. No. 14/997,892, filed on Jan. 18, 2016 and U.S. Provisional Patent Application No. 62/104,513, filed on Jan. 16, 2015, the disclosures of which are incorporated herein by reference in their entireties. Rails  1200 S may be mounted to one or more of the vertical and horizontal support members  1212 ,  1200  in, for example, picking aisles  130 A and be configured so that the bots  110  ride along the rails  1200 S through the picking aisles  130 A. At least one side of at least one of the picking aisles  130 A of at least one storage level  130 L may have one or more storage shelves (e.g. formed by rails  1210 ,  1200  and slats  1210 S) provided at differing heights so as to form multiple shelf levels  130 LS 1 - 130 LS 2  (although two levels are illustrated any number of levels may be provided and the picking aisle can be divided into sections SECA, SECB each having a different number of levels or the same number of levels) between the storage or deck levels  130 L defined by the transfer decks  130 B (and the rails  1200 S which form an aisle deck). Accordingly, there are multiple rack shelf levels  130 LS 1 - 130 LS 2 , corresponding to each storage level  130 L, extending along one or more picking aisles  130 A communicating with the transfer deck  130 B of the respective storage level  130 L. As may be realized, the multiple rack shelf levels  130 LS 1 - 130 LS 2  effect each storage level  130 L having stacks of stored case units (or case layers) that are accessible from a common deck  1200 S of a respective storage level  130 L (e.g. the stacks of stored cases are located between storage levels). In one aspect, referring to  FIG.  1 C  each of the storage levels  130 L includes a single level of storage shelves to store a single level of case units (e.g. each storage level includes a single case unit support plane CUSP) and the bots  110  are configured to transfer case units to and from the storage shelves of the respective storage level  130 L. 
     As may be realized, bots  110  traversing a picking aisle  130 A, at a corresponding storage level  130 L, have access (e.g. for picking and placing case units) to each storage space  130 S that is available on each shelf level  130 LS 1 - 130 LS 2 , where each shelf level  130 LS 1 - 130 LS 2  is located between the storage levels  130 L on one or more side(s) PAS 1 , PAS 2  (see e.g.  FIG.  3 A ) of the picking aisle  130 A. As noted above, each of the storage shelf levels  130 LS 1 - 130 LS 2  is accessible by the bot  110  from the rails  1200 S (e.g. from a common picking aisle deck  1200 S that corresponds with a transfer deck  130 B on a respective storage level  130 L). As can be seen in  FIG.  1 A  there are one or more shelf rails  1210  vertically spaced (e.g. in the Z direction) from one another to form multiple stacked storage spaces  130 S each being accessible by the bot  110  from the common rails  1200 S. As may be realized, the horizontal support members  1200  also form shelf rails (in addition to shelf rails  1210 ) on which case units are placed. Here the bots  110  includes a transfer arm  110 PA having a vertical drive axis configured to transfer case units to each of the shelf levels  130 LS 1 - 130 LS 2  from the common picking aisle deck. A suitable example of bot that services multiple shelf levels from a common picking aisle deck can be found in, for example, U.S. patent application Ser. No. 14/997,892, filed on Jan. 18 2016 and U.S. Provisional Patent Application No. 62/104,513 filed on Jan. 16, 2015, the disclosures of which are incorporated herein by reference in their entireties. In other aspects, where each storage level  130 L includes a single level of storage shelves as illustrated in  FIG.  1 B  the bot, such as bot  110 ′ (which is substantially similar to bot  110 ), is not provided with sufficient Z-travel of the transfer arm  110 PA for placing case units on the multiple storage shelf levels  130 LS 1 - 130 LS 2  (e.g. accessible from a common rail  1200 S) as described above. Here the transfer arm drive of the bots  110 ′ includes only sufficient Z-travel for lifting the case units from the case unit support plane CUSP of the single level of storage shelves, for transferring the case units to and from the payload area  110 PL and for transferring the case units between the transfer arm  110 PA and the payload bed  110 PB of the payload area  110 PL. Suitable examples of bots  110 ′ can be found in, for example, U.S. patent application Ser. No. 13/326,993 filed on Dec. 15, 2011, the disclosure of which is incorporated herein by reference in its entirety. 
     Each stacked shelf level  130 LS 1 - 130 LS 2  (and/or each single shelf level) of a corresponding storage level  130 L defines an open and undeterministic two dimensional storage surface (e.g. having a case unit support plane CUSP as shown in  FIG.  1 A ) that facilitates a dynamic allocation of pickfaces both longitudinally (i.e. along a length the aisle or coincident with a path of bot travel defined by the picking aisle) and laterally (i.e. transverse to the aisle or the path of bot travel). Dynamic allocation of the pickfaces and case units that make up the pickfaces is provided, for example, in the manner described in U.S. Pat. No. 8,594,835 issued on Nov. 26, 2013, the disclosure of which is incorporated by reference herein in its entirety. As such, case unit (or tote) pickfaces of variable lengths and widths are positioned at each two dimensional storage location on the storage shelves (e.g. on each storage shelf level  130 LS 1 - 130 LS 2 ) with minimum gaps (e.g. that effect picking/placing of case units free from contact with other case units stored on the shelves) between adjacent stored case units/storage spaces. In one aspect, the storage space(s)  130 S defined by the storage shelf levels  130 LS 1 - 130 LS 4  between the storage or deck levels  130 L accommodates case units of different heights, lengths, widths and/or weights at the different shelf levels  130 LS 1 - 130 LS 2  as described in, for example, U.S. patent application Ser. No. 14/966,978, filed on Dec. 11, 2015 (now U.S. Pat. No. 9,884,719) and U.S. Provisional Patent Application No. 62/091,162 filed on Dec. 12, 2014, the disclosures of which are incorporated by reference herein in their entireties. 
     Referring again to  FIG.  3 A and  3 B  each transfer deck  130 B or storage level  130 L includes one or more lift interface stations TS where case unit(s) (of single or combined case pickfaces) or totes are transferred between the lift load handling devices LHD and bots  110  on the transfer deck  130 B. The interface stations TS (and buffer stations SB described herein) provide an interface between the bots  110  on a respective transfer deck  130 B and at least one lift  150  to effect transfer of a pickface between the bots  110  and the at least one lift  150 . The one or more lift interface stations TS of one or more of the transfer deck or storage levels  130 L have multi-load stations MLS for positioning and/or buffering loads CU (such as the case units) for picking by the lifts  150 B. As described herein, in one aspect, each load is a pickface of one or more case units picked/placed as a unit at the multi-load station MLS by one or more of the bots  110  and the load handling device(s) LHD of lifts  150 B. In one aspect, the case units of each load/pickface are disposed in a load out as a unit or, in other aspects, are distributed in the load out. As will be described herein, each lift  150  includes a carriage  4001  that has a multi-load platform configured for a common multi-load lift/lower so as to, in one aspect, effect a multi-load pick (e.g. from a common interface station TS with a common/single load handling device LHD or with multiple independent load handling devices LHDs) or, in another aspect, effect multiple independent load picks (e.g. such as from interface stations TS at different deck levels) in a single lift pass. As may be realized, in one aspect, multi-loads (e.g. multiple pickfaces carried together as a single load or unit) are positioned at one or more of the interface stations TS (or buffer stations BS) for picking by the lifts  150 . 
     The interface stations TS are located at a side of the transfer deck  130 B opposite the picking aisles  130 A and rack modules RM, so that the transfer deck  130 B is interposed between the picking aisles and each interface station TS. As noted above, each bot  110  on each picking level  130 L has access to each storage location  130 S, each picking aisle  130 A and each lift  150  on the respective storage level  130 L, as such each bot  110  also has access to each interface station TS on the respective level  130 L. In one aspect the interface stations are offset from high speed bot travel paths HSTP along the transfer deck  130 B so that bot  110  access to the interface stations TS is undeterministic to bot speed on a high speed travel path HSTP. As such, each bot  110  can move a case unit(s) (or pickface, e.g. one or more cases, built by the bot) from every interface station TS to every storage space  130 S corresponding to the deck level and vice versa. 
     In one aspect the interface stations TS are configured for a passive transfer of case units between the bot  110  and the load handing devices LHD of the lifts  150  (e.g. the interface stations TS have no moving parts for transporting the case units) which will be described in greater detail below. For example, also referring to  FIG.  3 B  the interface stations include one or more stacked levels TL 1 , TL 2  of transfer rack shelves RTS which in one aspect are substantially similar to the storage shelves described above (e.g. each being formed by rails  1210 ,  1200  and slats  1210 S) such that bot  110  handoff (e.g. pick and place) as well as load handling device LHD handoff (e.g. pick and place) of case units (e.g. individual case units or pickfaces) and totes to the stacked rack shelves RTS (and/or the single level rack shelves) occurs in a passive manner substantially similar to that between the bot  110  and the storage spaces  130 S (as described herein) where the case units or totes are transferred to and from the shelves. In other aspects the shelves may include any suitable transfer arms (substantially similar to the load handling devices LHD of the lifts  150  shown in  FIGS.  5 A- 5 E , although Z direction movement may be omitted when the transfer arm is incorporated into the interface station TS shelves) for picking and placing case units or totes from one or more of the bot  110  and load handling device LHD of the lift  150 . Suitable examples of an interface station with an active transfer arm are described in, for example, U.S. patent application Ser. No. 12/757,354 filed on Apr. 9, 2010, the disclosure of which is incorporated by reference herein in its entirety. 
     In one aspect, the location of the bot  110  relative to the interface stations TS occurs in a manner substantially similar to bot location relative to the storage spaces  130 S. For example, in one aspect, location of the bot  110  relative to the storage spaces  130 S and the interface stations TS occurs in a manner substantially similar to that described in U.S. patent application Ser. No. 13/327,035 filed on Dec. 15, 2011, (now U.S. Pat. No. 9,008,884) and Ser. No. 13/608,877 filed on Sep. 10, 2012, (now U.S. Pat. No. 8,954,188), the disclosures of which are incorporated herein by reference in their entireties. For example, referring to  FIGS.  1  and  1 A , the bot  110  includes one or more sensors  110 S that detect the slats  1210 S or a locating feature  130 F (such as an aperture, reflective surface, RFID tag, etc.) disposed on/in the rail  1200 . The slats and/or locating features  130 F are arranged so as to identify a location of the bot  110  within the storage and retrieval system, relative to e.g. the storage spaces and/or interface stations TS. In one aspect the bot  110  includes a controller  110 C that, for example, counts the slats  1210 S to at least in part determine a location of the bot  110  within the storage and retrieval system  100 . In other aspects the location features  130 F may be arranged so as to form an absolute or incremental encoder which when detected by the bot  110  provides for a bot  110  location determination within the storage and retrieval system  100 . 
     As may be realized, referring to  FIG.  3 B , the transfer rack shelves RTS at each interface station TS define the multi-load stations MLS (e.g. having one or more storage case unit holding locations for holding a corresponding number of case units or totes) on a common transfer rack shelf RTS. As noted above, each load of the multi-load station is a single case unit/tote or a multi-case pickface (e.g. having multiple case units/totes that are moved as a single unit) that is picked and paced by either the bot or load handling device LHD. As may also be realized, the bot location described above allows for the bot  110  to position itself relative to the multi-load stations MLS for picking and placing the case units/totes and pickfaces from a predetermined one of the holding locations of the multi-load station MLS. The interface stations TS define buffers where inbound and/or outbound case units/totes and pickfaces are temporarily stored when being transferred between the bots  110  and the load handling devices LHD of the lifts  150 . 
     In one aspect one or more peripheral buffer stations BS (substantially similar to the interface stations) are also located at the side of the transfer deck  130 B opposite the picking aisles  130 A and rack modules RM, so that the transfer deck  130 B is interposed between the picking aisles and each buffer station BS. The peripheral buffer stations BS are interspersed between or, in one aspect as shown in  FIGS.  3 A and  3 B , otherwise in line with the interface stations TS. In one aspect the peripheral buffer stations BS are formed by rails  1210 ,  1200  and slats  1210 S and are a continuation of (but a separate section of) the interface stations TS (e.g. the interface stations and the peripheral buffer stations are formed by common rails  1210 ,  1200 ). As such, the peripheral buffer stations BS also include one or more stacked levels TL 1 , TL 2  of transfer rack shelves RTS as described above with respect to the interface stations TS. The peripheral buffer stations BS define buffers where case units/totes and/or pickfaces are temporarily stored for any suitable reasons such as when being transferred from one bot  110  to another different bot  110  on the same storage level  130 L. As maybe realized, in one aspect the peripheral buffer stations BS are located at any suitable location of the storage and retrieval system including within the picking aisles  130 A and anywhere along the transfer deck  130 B. 
     Still referring to  FIGS.  3 A and  3 B  in one aspect the interface stations TS are arranged along the transfer deck  130 B in a manner akin to parking spaces on the side of a road such that the bots  110  “parallel park” at a predetermined interface station TS for transferring case units to and from one or more shelves RTS at one or more levels TL 1 , TL 2  of the interface station TS. In one aspect, a transfer orientation of the bots  110  (e.g. when parallel parked) at an interface station TS is the same orientation as when the bot  110  is travelling along the high speed bot transport path HSTP (e.g. the interface station is substantially parallel with a bot travel direction of the transfer deck and/or a side of the transfer deck on which the lifts  150  are located). Bot  110  interface with the peripheral buffer stations BS occurs by parallel parking so that a transfer orientation of the bots  110  (e.g. when parallel parked) at a peripheral buffer station BS is the same orientation as when the bot  110  is travelling along the high speed bot transport path HSTP. 
     In another aspect, referring to  FIGS.  4 A and  4 B , at least the interface stations TS are located on an extension portion or pier  130 BD that extends from the transfer deck  130 B. In one aspect, the pier  130 BD is similar to the picking aisles where the bot  110  travels along rails  1200 S affixed to horizontal support members  1200  (in a manner substantially similar to that described above). In other aspects, the travel surface of the pier  130 BD may be substantially similar to that of the transfer deck  130 B. Each pier  130 BD is located at the side of the transfer deck  130 B, such as a side that is opposite the picking aisles  130 A and rack modules RM, so that the transfer deck  130 B is interposed between the picking aisles and each pier  130 BD. The pier(s)  130 BD extends from the transfer deck at a non-zero angle relative to at least a portion of the high speed bot transport path HSTP. In other aspects the pier(s)  130 BD extend from any suitable portion of the transfer deck  130 B including the ends  130 BE 1 ,  130 BE 2  of the transfer deck  130 BD. As may be realized, peripheral buffer stations BSD (substantially similar to peripheral buffers stations BS described above) may also be located at least along a portion of the pier  130 BD. 
     Referring now to  FIGS.  5 A,  5 B and  5 C , as described above, in one aspect the interface stations TS are passive stations and as such the load transfer device LHD of the lifts  150 A,  150 B have active transfer arms or pick heads  4000 A,  4000 B. In one aspect the lifts  150  communicating between the input and output conveyors  160 CA,  160 CB and one or more of the interface station(s) TS (which in one aspect include stacked transfer rack shelves RTS) of the stacked deck levels  130 B are reciprocating lifts, e.g. the lifts bi-directionally travel in the Z direction (relative to a reference frame of the lift as shown in  FIG.  5 C ) linearly along a single straight line path. The lifts  150  are unconstrained in their rate of travel in the Z direction and are high speed lifts (rather than a continuous motion or paternoster type lift) where a transfer rate or speed of the lift is not a delimiting factor in the transfer of case units to and from the storage and retrieval system. For example, a case unit transfer transaction rate of the lifts  150  is substantially equal to a case unit transfer transaction rate of the bots  110 . As may be realized, while the input and output lifts  150 A,  150 B are described as vertically reciprocating lifts it should be understood that in other aspects the input and output lifts  150 A,  150 B are any suitable pickface transport system for transporting case pickfaces to and from the storage structure  130 . For example, in other aspects the lift modules  150 A,  150 B are one or more of vertically reciprocating lifts, any suitable automated material handling systems, conveyors, bots, turntables, roller beds, multilevel vertical conveyor (e.g. paternoster conveyor) that operate synchronously or asynchronously. 
     As described herein, the lifts  150  traverse and connect more than one level  130 L of the multilevel transfer decks  130 B and are arranged for lifting and lowering a pickface from the multilevel transfer decks  130 B. As also described herein, multi-loads placed at, for example, the interface stations TS are picked with load handling devices LHD of the lifts  150  and transported by the lifts  150  in a single pass/traverse of the multiple deck levels  130 B to an off load conveyor station, such as outbound conveyor  160 CB. As noted herein, the multi-load pick, in one aspect, is a common pick from a common interface station TS (effected with the common load handling device LHD or by multiple independent load handling devices LHD) so that the multi-load pick is effected in one lift stop. In other aspects, the multi-load is picked from different interface stations TS at different levels  130 L of the multilevel transfer decks  130 B, and hence with multiple lift stops, but still within a single pass/traverse of the multiple deck levels (e.g. with no change in lift travel direction and/or cyclic motion). As will be described further herein, the case loads/pickfaces delivered to the output stations  160 UT by the lifts  150  are considered to form a case load stream (e.g. where each lift  150  produces one case load stream). 
     Referring to, for example,  FIGS.  5 A- 5 E , in one aspect, the pick heads (such as pick heads  4000 A,  4000 B,  4000 C,  4000 D) of each lift  150  include a multi-load (e.g. multiple pickfaces carried together as a single load or unit) platform (such a load handling device LHD) that is configured for a common multi-load lifting/lowering (e.g. relative to, for example, the multiple levels  130 L of the storage and retrieval system). In one aspect, the pick head  4000 A,  4000 B,  4000 C,  4000 D effects a multi-load pick (e.g. from a common interface station with a common/single load handling device LHD or with multiple independently operable load handling devices LHDs). In another aspect, the pick head  4000 A,  4000 B,  4000 C,  4000 D effects multiple independent load picks (e.g. such as from different interface stations TS arranged on difference levels  130 L of the storage and retrieval system) in a single pass/traverse to an off load conveyor station(s) (e.g. such as outbound conveyors  160 CB— FIG.  1   ) or any other suitable pickface holding/transport stations. Accordingly, multi-loads are positioned at each or in other aspects, one or more, interface stations TS for picking by the lift  150 (s). As may be realized, the multi-load(s) at each or any interface station TS is picked by a load handling device LHD of the lift  150  and transported by the lift  150  in a single pass/traversal of the pick head  4000 A,  4000 B relative to the levels  130 L of the storage and retrieval system to, for example, the output conveyor  160 CB of output station(s)  160 UT or other suitable pickface holding/transport station. As noted above, the multi-load pick is, in one aspect, a common pick from a common interface station TS (effected with the common load handling device or by multiple independent load handling devices LHDs so that the multi-load pickface is effected in one stop of the pick head  4000 A,  4000 B). In other aspects, the multi-load pick is picked from different interface stations TS at different level  130 L of the storage and retrieval system, and hence multiple stops (but still having with a single pass/traverse—e.g. no change in direction or cyclic motion of the pick head  4000 A,  4000 B). 
     In one aspect the inbound lift modules  150 A and the outbound lift modules  150 B have different types of pick heads (as will be described below) while in other aspects the inbound lift modules  150 A and the outbound lift modules  150 B have the same type of pick head similar to one of the pick heads described below (e.g. both the lifts  150 A,  150 B have pick head  4000 A or both lifts  150 A,  150 B have pick head  4000 B). For example, both the inbound and outbound lift modules  150 A,  150 B have a vertical mast  4002  (while one mast is illustrated, in other aspects there are multiple masts). The vertical mast(s)  4002  spans between a base level BL ( FIG.  3 B ), such as where, for example, the input and output conveyors  160 CA,  160 CB of the input and output stations  160 IN,  160 UT are located, and any desired decks or storage levels  130 L of the multi-level storage array. One or more carriage(s) or slide(s)  4001  travel along the vertical mast(s)  4002  under the motive force of any suitable drive unit  4002 D (e.g. connected to, for example, control server  120 ) configured to lift and lower the slide (and the pick head  4000 A,  4000 B mounted thereto) between the base level BL and any desired interface station shelf at a desired storage level  130 L. The drive unit  4002 D is one or more of a chain drive, a belt drive, a screw drive, a linear actuator, a solid state drive or any other drive capable of linearly driving the slide(s) and pick heads  4000 A,  4000 B mounted thereto along the mast(s)  4002 . 
     As may be realized, the lifts  150  include any suitable pick head positioning system for positioning the pick head(s)  4000 A,  4000 B relative to the interface station TS shelves. For example, any suitable encoders or position sensors SENS are provided which, along with control server  120 , provide for position determination of the pick head(s)  4000 A,  4000 B relative to the interface station TS shelves and input/output conveyors  160 CA,  160 CB. For example, the control server  120  provides control signals to the lift drives  4002 D,  4005 ,  4005 A. The control server  120  also receives signals from the position sensors SENS as the pick head(s) move along the mast  4002  and determines, based on the signals a location of the pick heads relative to the interface station TS shelves. The control server  120  stops the pick head(s) at a predetermined interface station shelf based on the sensor SENS signals and effects extension of the load handling device LHD as will be described in greater detail below to pick or place one or more case unit(s) to the interface station TS shelves. 
     As noted above, the inbound lift module(s)  150 A include a pick head  4000 A that is movably dependent from the mast(s)  4002 , such as by being mounted to the slide(s)  4001  so that as the slide(s) moves vertically the pick head  4000 A moves vertically with the slide(s)  4001 . In this aspect the pick head  4000 A includes a pick head portion or effector LHDA having one or more tines or fingers  4273  mounted to a base member  4272  so as to form a platform PFM for housing loads. The fingers  4273  are configured to pass through or otherwise between the slats  1210 S of the interface stations TS shelves for transferring one or more case unit(s) between the load handling device LHD and the shelves (as will be described in greater detail below). The base member  4272  is movably mounted to one or more rail  4360 S of frame  4200  which in turn is mounted to the slide  4001 . Any suitable drive unit  4005 , such as a belt drive, chain drive, screw drive, gear drive, etc. (which is substantially similar in form but may not be similar in capacity to drive  4002 D as the drive  4005  may be smaller than drive  4002 D) is mounted to the frame  4200  and coupled to the base member  4272  for driving the base member  4272  (with the finger(s), i.e. the effector LHDA) in the direction of arrow  4050  (e.g. the Y direction relative to a lift reference frame REFL). The load platform PFM includes one or more load stations LST 1 -LST 3 , each being arranged for holding a case unit(s)/tote or pickface thereon. In one aspect each platform PFM is illustrated has having three load stations LST 1 -LST 3  but in other aspects the platforms have more or less than three load stations. Each of the case unit(s)/tote or pickface in the one or more load stations LST 1 -LST 3  is transferred to and from the lift  150  as a unit but it should be understood that where there are multiple case unit(s)/tote(s) in a load station (e.g. a pickface) the pickface, in one aspect is broken up so that one or more case units that form the pickface are distributed to a different section of the storage level  130 L than other case unit(s) of that pickface while in other aspects the pickface may be placed within a storage space  130 S as a unit in the manner described, for example, in U.S. patent application Ser. No. 14/997,892, filed on Jan. 18, 2016 and U.S. Provisional Patent Application No. 62,104,513 filed on Jan. 16, 2015, the disclosures of which were previously incorporated herein by reference in their entireties. 
     The outbound lift module(s)  150 B also include a pick head  4000 B mounted to the slide  4001  so that as the slide moves vertically the pick head  4000 B moves vertically with the slide  4001 . In this aspect the pick head  4000 B includes one or more pick head portions or effectors LHDA, LHDB (which are each substantially similar to pick head  400 A) each having one or more tines or fingers  4273  mounted to a respective base member  4272 A. Each base member  4272 A is movably mounted to one or more rail  4360 SA of frame  4200 A which in turn is mounted to the slide  4001 . Any suitable drive unit(s)  4005 A, such as a belt drive, chain drive, screw drive, gear drive, etc. is mounted to the frame  4200 A and coupled to a respective base member  4272 A for driving the respective base member  4272 A (with the finger(s)) in the direction of arrow  4050  (each effector has a respective drive unit so that each effector is independently movable in the direction of arrow  4050 ). While two effectors LHDA, LHDB are illustrated on pick head  4000 B the pick head  4000 B includes any suitable number of effectors that correspond to a number of case unit/pickface holding locations of, for example, the interface stations TS so that case units/pickfaces are individually picked from the interface stations TS are described in greater detail below. 
     In one aspect, referring also to  FIG.  5 D , one or more of the input and output lifts  150  includes multiple pick heads  4000 C,  4000 D each mounted to a corresponding carriage or slide  4001 A,  4001 B. Each of the slides  4001 A,  4001 B (and the pick head mounted thereto) is mounted to the mast  4002  so as to be independently moveable in the Z direction by a respective drive  4002 DA,  4002 DB (which is substantially similar to drive  4002 D described above). While each pick head  4000 C,  4000 D illustrated in  FIG.  5 D  includes a single load handling device it should be understood that one or more of the pick heads, in other aspects,  4000 C,  4000 D includes multiple independently actuated load handling devices in a manner similar to pick head  4000 B. As may also be realized, suitable clearance is provided between each of the slides  4001 A,  4001 B and the pick head(s) mounted thereto so that each pick head is provided with the full stroke of travel (e.g. from the base level BL ( FIG.  3 A ) to, for example, the interface station shelves at the top storage level  130 L) along the mast  4002  as desired. 
     In another aspect each load handling device LHD, as described above, of the lifts  150 A,  150 B is configured to sort one or more case units onboard the load handling device for building pickfaces on the load handling device. For example, referring to  FIG.  5 E  the carriage  4200 B includes a frame  4110 F having a payload section  4110 PL. The payload section  4110 PL of the load handling device LHD includes a payload bed  4110 PB, a fence or datum member  4110 PF, a transfer arm LHDA and a pusher bar or member  4110 PR. In one aspect the payload bed  4110 PB includes one or more rollers  4110 RL that are mounted to the frame  110 F so as to be substantially parallel with the fingers  4273 A- 4273 E where one or more case units carried within the payload section  110 PL can be moved in the X direction (e.g. justified with respect to a predetermined location of the frame/payload section and/or a datum reference of one or more case units in the lift frame of reference REFL) to position the case unit at a predetermined position within the payload section  4110 PL and/or relative to other case units within the payload section  4110 PL (e.g. side to side justification of case units as opposed to fore/aft as defined by the direction of extension of the transfer arm LHDA as described below, e.g. in the Y direction relative to the lift frame of reference). In one aspect the rollers  4110 RL may be driven (e.g. rotated about their respective axes) by any suitable motor for moving the case units within the payload section  4110 PL. In other aspects the load handling device LHD includes one or more side justification movable pusher bar (not shown) for pushing the case units over the rollers  4110 RL for moving the case unit(s) to the predetermined position within the payload section  4110 PL along the X direction. The side justification movable pusher bar may be substantially similar to that described in, for example, U.S. patent application Ser. No. 13/326,952 filed on Dec. 15, 2011, the disclosure of which was previously incorporated by reference herein in its entirety. The pusher bar  4110 PR is movable in the Y direction, relative to the lift reference frame REFL to effect, along with the fence  4110 PF and or pick head  4270  of the transfer arm LDHA, a fore/aft justification of case unit(s) within the payload area  4110 PL in the manner described in U.S. Provisional Patent Application No. 62/107,135 filed on Jan. 23, 2015, previously incorporated herein by reference in their entireties. 
     Still referring to  FIG.  5 E , the case units are placed on the payload bed  4110 PB and removed from the payload bed  4110 PB with the transfer arm LHDA. The transfer arm LHDA includes a lift mechanism or unit  5000  located substantially within the payload section  4110 PL as described in, for example, U.S. Provisional Patent Application No. 62/107,135 filed on Jan. 23, 2015, previously incorporated herein by reference in their entireties. The lift mechanism  5000  provides, in addition to or in lieu of movement of the carriage  4200 B in the Z direction, both gross and fine positioning of pickfaces carried by the load handling device LHD which are to be lifted vertically into position in the storage structure  130  for picking and/or placing the pickfaces and/or individual case units to and from the shelves of the interface stations TS. 
     The lift mechanism  5000  is configured so that combined axis moves are performed (e.g. combined substantially simultaneous movement of the pusher bar  4110 PR, lift mechanism  5000 , pick head extension and fore/aft justification mechanism(s)), so that different/multi-sku or multi-pick payloads are handled by the lift  150 . In one aspect, the actuation of the lifting mechanism  5000  is independent of actuation of the pusher bar  4110 PR as will be described below. The decoupling of the lift mechanism  5000  and pusher bar  4110 PR axes provides for combined pick/place sequences effecting a decreased pick/place cycle time, increased storage and retrieval system throughput and/or increased storage density of the storage and retrieval system as described above. For example, the lift mechanism  5000  provides for lifting case units from the payload bed  4110 PL of the load handling device LHD to allow for sorting and justifying case units to predetermined positions on the payload bed  41110 PL and thus on the transfer arm LHDA. In one aspect the case units are lowered on the payload bed if sorting or justification is desired, otherwise the transfer arm LHDA may remain at least partially lifted to allow the arm to extend and retract for picking/placing case units to/from the interface stations TS without a secondary lifting of the transfer arm LHDA above the fence  4110 PF in addition to, for example, traversal of the load handling device LHD along the mast(s)  4002 . 
     The lifting mechanism  5000  may be configured in any suitable manner so that a pick head  4270  of the load handling device LHD bi-directionally (e.g. reciprocates) moves along the Z axis (e.g. in the Z direction). In one aspect, the lifting mechanism  5000  includes a mast  5000 M and the pick head  4270  is movably mounted to the mast  4200 M in any suitable manner. The mast  4200 M is movably mounted to the frame  4110 F in any suitable manner so as to be movable along the Y direction. In one aspect the frame includes guide rails  4360 S to which the mast  4200 M is slidably mounted. A transfer arm drive  4005  may be mounted to the frame for effecting at least movement of the transfer arm LHDA along the Y direction and the Z direction. In one aspect the transfer arm drive  4005  includes an extension motor  4301  and a lift motor  4302 . The extension motor  4301  may be mounted to the frame  4110 F and coupled to the mast  4200 M in any suitable manner such as by a belt and pulley transmission  4260 A, a screw drive transmission (not shown) and/or a gear drive transmission (not shown). The lift motor  4302  may be mounted to the mast  4200 M and coupled to pick head  4270  by any suitable transmission, such as by a belt and pulley transmission  4271 , a screw drive transmission (not shown) and/or a gear drive transmission (not shown). As an example, the mast  4200 M includes guides, such as guide rails  4280 , along which the pick head  4270  is mounted for guided movement in the Z direction along the guide rails  4280 . In other aspects the pick head  4270  is mounted to the mast in any suitable manner for guided movement in the Z direction. With respect to the transmissions In other aspects any suitable linear actuators are used to move the pick head in the Z direction. The transmission  260 A for the extension motor  301  is substantially similar to that described herein with respect to transmission  271 . 
     Still referring to  FIG.  5 E  the pick head  4270  of the load handling device LHD transfers case units between the load handling device LHD and interface stations TS (see e.g.  FIG.  3 A ) and in other aspects substantially directly between the bot  110  and a lift module(s)  150 . In one aspect, the pick head  4270  includes a base member  4200 B 1 , one or more tines or fingers  4273 A- 4273 E and one or more actuators  4274 A,  4274 B. The base member  4200 B 1  is mounted to the mast  4200 M, as described above, so as to ride along the guide rails  4280 . The one or more tines  4273 A- 4273 E are mounted to the base member  4200 B 1  at a proximate end of the tines  4273 A- 4273 E so that a distal end of the tines  4273 A- 4273 E (e.g. a free end) is cantilevered from the base member  4200 B 1 . Referring again to  FIG.  1 A , the tines  4273 A- 4273 E are configured for insertion between slats  1210 S that form the case unit support plane CUSP of the interface station TS shelves. 
     One or more of the tines  4273 A- 4273 E is movably mounted to the base member  4200 B 1  (such as on a slide/guide rail similar to that described above) so as to be movable in the Z direction. In one aspect any number of tines are mounted to the base member  4200 B 1  while in the aspect illustrated in the figures there are, for example, five tines  4273 A- 4273 E mounted to the base member  4200 B 1 . Any number of the tines  4273 A- 4273 E are movably mounted to the base member  4200 B 1  while in the aspect illustrated in the figures, for example, the outermost (with respect to a centerline CL of the pick head  4270 ) tines  4273 A,  4273 E are movably mounted to the base member  4200 B 1  while the remaining tines  4273 B- 4273 D are immovable relative to the base member  4200 B 1 . 
     In this aspect the pick head  4270  employs as few as three tines  4273 B- 4273 D to transfer smaller sized case units (and/or groups of case units) to and from the load handling device LHD and as many as five tines  4273 A- 4273 E to transfer larger sized case units (and/or groups of case units) to and from the load handling device LHD. In other aspects, less than three tines are employed (e.g. such as where more than two tines are movably mounted to the base member  4200 B 1 ) to transfer smaller sized case units. For example, in one aspect all but one tine  4273 A- 4273 E is movably mounted to the base member  4200 B 1  so that the smallest case unit being transferred to and from the load handling device without disturbing other case units on, for example, the shelves of the interface stations has a width of about the distance X 1  between slats  1210 S (see  FIG.  1 A ). 
     The immovable tines  4273 B- 4273 D define a picking plane SP of the pick head  4270  and are used when transferring all sizes of case units (and/or pickfaces) while the movable tines  4273 A,  4273 E are selectively raised and lowered (e.g. in the Z direction with the actuators  274 A,  274 B) relative to the immovable tines  4273 B- 4273 D to transfer larger case units (and/or pickfaces). Still referring to  FIG.  5 E  an example is shown where all of the tines  4273 A- 4273 E are positioned so that a case unit support surface SF of each tine  4273 A- 4273 E is coincident with the picking plane SP of the pick head  4270  however, as may be realized, the two end tines  4273 A,  4273 E are movable so as to be positioned lower (e.g. in the Z direction) relative to the other tines  4273 B- 4273 D so that the case unit support surface SF of tines  4273 A,  4273 E is offset from (e.g. below) the picking plane SP so that the tines  4273 A,  4273 E do not contact the one or more case units carried by the pick head  4270  and do not interfere with any unpicked case units positioned in predetermined case unit holding locations on the interface station TS shelves. 
     The movement of the tines  4273 A- 4273 E in the Z direction is effected by the one or more actuators  4274 A,  4274 B mounted at any suitable location of the transfer arm LHDA. In one aspect, the one or more actuators  4274 A,  4274 B are mounted to the base member  4200 B 1  of the pick head  4270 . The one or more actuators are any suitable actuators, such as linear actuators, capable of moving one or more tines  4273 A- 4273 E in the Z direction. In the aspect illustrated in, for example,  FIG.  5 E  there is one actuator  4274 A,  4274 B for each of the movable tines  4273 A,  4273 E so that each moveable tine is independently movable in the Z direction. In other aspects one actuator may be coupled to more than one movable tine so that the more than one movable tine move as a unit in the Z direction. 
     As may be realized, movably mounting one or more tines  4273 A- 4273 E on the base member  4200 B 1  of the pick head  4270  provides for full support of large case units and/or pickfaces on the pick head  4270  while also providing the ability to pick and place small case units without interfering with other case units positioned on, for example, the shelves of interface stations TS. The ability to pick and place variably sized case units without interfering with other case units at the interface stations reduces a size of a gap G ( FIG.  6   ) between case units on the interface stations shelves 
     Referring again to  FIG.  5 E , it is again noted that the pusher bar  4110 PR is movable independent of the transfer arm LHDA. The pusher bar  4110 PR is movably mounted to the frame  4110 F in any suitable manner such as by, for example, a guide rod and slide arrangement and is actuated along the Y direction (e.g. in a direction substantially parallel to the extension/retraction direction of the transfer arm LHDA). In one aspect at least one guide rod  4360  is mounted within the payload section  4110 PL for guiding movement of the pusher  4110 PR in the Y direction. In one aspect, at least the guide rod/slide arrangement holds the pusher bar  4110 PR captive within the payload section  4110 PL. The pusher bar  4110 PR is actuated by any suitable motor and transmission, such as by motor  4303  and transmission  4303 T. In one aspect the motor  4303  is a rotary motor and the transmission  4303 T is a belt and pulley transmission. In other aspects the pusher bar  110 PR may be actuated by a linear actuator having substantially no rotary components. 
     The pusher bar  4110 PR is arranged within the payload section  4110 PL so as to be substantially perpendicular to the rollers  4110 RL and so that the pusher bar  4110 PR does not interfere with the pick head  4270  (the pusher bar  4110 PR includes slots  4351  into which the fingers  4273 A- 4273 E pass when lowered into the payload bed  4110 PB where the slots  4351  are sized to allow unhindered movement of the pusher bar relative to the fingers  4273 A- 4273 E). The pusher bar  4110 PR also includes one or more apertures through which the rollers  4110 RL pass where the apertures are sized to allow free rotation of the rollers about their respective axes. As may be realized, the independently operable pusher bar  4110 PR does not interfere with the rollers  4110 PR, extension of the transfer arm LHDA in the transverse direction (e.g. Y direction) and the lifting/lowering of the pick head  4270 . 
     As may be realized, the lift modules  150 A,  150 B are under the control of any suitable controller, such as control server  120 , such that when picking and placing case unit(s) the pick head is raised and/or lowered to a predetermined height corresponding to a shelf of an interface station TS at a predetermined storage level  130 L. At the interface stations TS the pick head  4000 A,  4000 B,  4270  or individual portion thereof (e.g. effector LHDA, LHDB), corresponding to one or more case unit holding location(s) of the interface station TS from which one or more case unit(s) are being picked, is extended so that the fingers  4273  are interdigitated between the slats  1210 S (as illustrated in  FIG.  5 B ) underneath the case unit(s) being picked. The lift  150 A,  150 B raises the pick head  4000 A,  4000 B,  4270  to lift the case unit(s) from the slats  1210 S and retracts the pick head  4000 A,  4000 B,  4270  for transport of the case unit(s) to another level of the storage and retrieval system, such as for transporting the case unit(s) to output station  160 UT. Similarly, to place one or more case unit(s) the pick head  4000 A,  4000 B,  4270  or individual portion thereof (e.g. effector LHDA, LHDB), corresponding to one or more case unit holding location(s) of the interface station TS from which one or more case unit(s) are being placed, is extended so that the fingers  4273  are above the slats. The lift  150 A,  150 B lowers the pick head  4000 A,  4000 B,  4270  to place the case unit(s) on the slats  1210 S and so that the fingers  4273  are interdigitated between the slats  1210 S underneath the case unit(s) being picked. 
     An example of a lift  150  case unit(s) transfer transaction including a case unit(s) multi-pick and place operation and on the fly sortation of the case units for creating a mixed pallet load MPL (as shown in  FIG.  2   ) according to a predetermined order/load out sequence and/or in the predetermined order sequence (e.g. an order/load out sequence) of picked items according to, for example, an order, fulfilling one or more customer orders, in which case units CU are sequenced for placement in one or more bag(s), tote(s) or other container(s) TOT at an operator station  160 EP (as shown in  FIG.  14   ) as will be described with respect to  FIGS.  5 A- 5 E,  6  and  7 - 7 E  in accordance with aspects of the disclosed embodiment. In one aspect, the control server  120  is configured to one or more of command the bot  110 , and effect with the bot  110  outbound flow (e.g. fulfillment stream) sortation of case order(s) independent of the pick order of cases from the storage area by the bot  110  forming a pickface (as described in U.S. patent application Ser. No. 14/997,892, filed on Jan. 18, 2016, previously incorporated by reference herein by reference), and command the lift(s)  150  and effect with the lift(s)  150  outbound flow (e.g. fulfillment stream) sortation of case orders independent of the order in which the case units were placed at, for example the transfer station(s) TS (or buffer stations BS) by the bot  110  (as described in U.S. patent application Ser. No. 14/997,902, filed on Jan. 18, 2016, previously incorporated herein by reference). In one aspect, the bot controller  110 C is configured to command the bot  110 , and effect with the bot  110  outbound flow sortation of case order(s) independent of the pick order of cases from the storage area by the bot  110  forming a pickface. In still other aspects, the control server  120  and the bot controller  110 C are both configured to command the bot  110 , and effect with the bot  110  outbound flow sortation of case order(s) independent of the pick order of cases from the storage area by the bot  110  forming a pickface. Thus, in one aspect, the control server  120  and/or the bot controller  110 C is/are configured to set the outbound case flow, at least in part with bot  110  sortation of the cases carried in common by the bot  110  and decoupled from the pick order of the cases by the bot  110  from storage. This may be referred to for description purposes as outbound flow sortation with the bot at transfer stations (and/or at buffer stations). In another aspect, the control server  120  and/or the lift(s)  150  is/are configured to set the outbound case flow, at least in part with lift  150  sortation of the cases carried in common by the lift  150  and decoupled from the pick order of the cases by the lift from the transfer stations TS (or buffer stations BS). This may be referred to for description purposes as outbound flow sortation with the lift at transfer stations (and/or at buffer stations). 
     In one aspect, multiple transfer decks  130 B are provided and arrayed at different levels so as to define multilevel decks in the manner described above ( FIG.  6 A , Block  900 ). One or more bots  110  are disposed on each of the multilevel decks  130 B, as described above, for holding and transporting pickfaces on each deck  130 B ( FIG.  6 A , Block  910 ). The pickfaces are lifted and/or lowered from the multilevel decks  130 B in accordance with a load out sequence, in a manner substantially similar to that described below, with at least one outbound lift  150 B that traverses and connects more than one level of the multilevel decks  130 B ( FIG.  6 A , Block  920 ). As may be realized, each load out (truck load, pallet load, etc. filled with cases from the storage and retrieval system  100 ) from the distribution center or warehouse, e.g. in which the storage and retrieval system  100  is located, has a predetermined sequence or order of caseloads (of single cases or combined cases) in which the case loads are integrated to fill the load out (e.g. the load out order sequence which is defined in any suitable manner such as that described in U.S. patent application Ser. No. 13/654,293 filed on Oct. 17, 2012 (now U.S. Pat. No. 8,965,559), previously incorporated herein by reference in its entirety, and/or a rules based system that is based on customer criteria, off load criteria or any other suitable criteria. As will be described below, transfer of the pickfaces (e.g. case loads) between the bot  110  and the at least one outbound lift  150 B is effected with at least one transfer station TS (or buffer station BS) on each deck that interfaces between the bot  110  on a respective transfer deck  130 B and the at least one outbound lift  150 B ( FIG.  6 A , Block  930 ). In one aspect, each outbound lift  150 B defines at least one case load stream of an order fulfillment stream (which may also be referred to as an outbound stream/flow or order fulfillment) that includes mixed case pickfaces outbound from the multilevel decks  130 B to a load out fill or load fill where at least one case load stream of the fulfillment stream is arranged in an ordered sequence of streaming pickfaces related to the predetermined sequence of the load out fill (e.g. the individual case load streams of the lifts  150 B form an order fulfillment stream corresponding to the load out fill) ( FIG.  6 A , Block  940 ). As may be realized, the at least one transfer station TS (or buffer station BS) on at least one of the multilevel decks commonly supports more than one of the mixed case pickfaces (e.g. that define a portion of the streaming pickfaces in the ordered sequence of streaming pickfaces) based on, for example, a predetermined sequence of the load out fill. In one aspect the interface station TS (or buffer station BS) forms a common pickface transfer interface for the at least one outbound lift  150 B, so that the commonly supported pickfaces are picked in common with the at least one outbound lift  150 B. In one aspect, the interface stations TS (or buffer stations BS) commonly support more than one of the mixed case pickfaces in an ordered sequence based on the predetermined sequence of the load out fill. As may be realized, any suitable controller, such as controller  120  is in communication with the one or more bots  110  and is configured to effect placement of pickfaces on the at least one transfer station TS (or buffer station BS) based on the ordered sequence of streaming pickfaces. In one aspect the ordered sequence of streaming pickfaces is based on another fulfillment stream of, for example, another outbound lift  150 B. As may be realized, if there is more than one case load stream (e.g. from multiple outbound lifts  150 B), the case loads of each case load stream are in a corresponding order sequence related to the predetermined sequence of the load out fill, as well as to each other, to provide a coordinated and harmonized integration of the case loads in each stream in the load out fill (e.g. the individual case load streams are combined according to the predetermined sequence of the load out fill to form the order fulfillment stream where the first ordered sequence of streaming pickfaces from a first lift complements the second ordered sequence of streaming pickfaces from a second lift) ( FIG.  6 A , Block  950 ). In one aspect, the ordered sequence of the case loads in each case load stream is defined by the ordered sequence of the multi-case loads of each load out (e.g. outbound) stroke of the outbound lift  150 B generating/feeding the case load stream (e.g. see  FIG.  1 B  where the sequencing  174  is performed by the vertical case transport  173  of the outbound lifts  150 B). In one aspect, the fulfillment stream sortation for each sortation system/method, as described herein, is based, at the sortation itself, on another fulfillment stream so that the sortation with the bot  110  at the transfer station TS (or buffer station BS) is dependent on a sequence of another fulfillment stream (such as by another bot at the same or a different transfer station TS), and the sortation by the lift  150  is dependent on another fulfillment stream (such as by another lift  150 ). 
     As an example, of case load streams, referring to  FIG.  6   , there are two outbound lifts  150 B 1 ,  150 B 2 , each lift having a respective case load stream COS 1 , COS 2  which is transferred to the outbound conveyors  160 CB through transfer stations  160 TS,  160 TSA (in other aspects there is any suitable number of outbound lifts with any suitable corresponding number of case load streams being provided to a load out fill). For example, the ordered sequence of the case loads in each case load stream COS 1 , COS 2  is defined by the ordered sequence of the multi-caseloads of each load out (outbound) stroke of the respective lift  150 B 1 ,  150 B 2  generating/feeding the case load stream COS 1 , COS 2  (e.g. the multi-loads of each lift load out stroke are arranged in the ordered sequence related to the fill sequence). Here the order fulfillment stream is defined by the two lifts  150 B 1 ,  15 B 2  however, in other aspects the order fulfillment stream is defined by one of the lifts  150 B 1 ,  150 B 2  independent of other ones of the lifts  150 B 1 ,  150 B 2 . 
     In one aspect, the sorting of the multi-loads to the ordered/fill sequence is effected both prior to lift pick and/or during lift pick. For example, sorting prior to lift pick includes case units/pickfaces (e.g. multi-case loads) being delivered by the bots  110  to interface station shelves  7000 A- 7000 L of the transfer stations TS of the different transfer deck levels  130 B. In one aspect the case load delivery timing of the case loads by the bots  110  to the transfer stations TS is not in sequence however, the case loads delivered correspond to the predetermined sequence of the case load stream COS 1 , COS 2  output by the respective outbound lift  150 B 1 ,  150 B 2  for effecting the ordered fill sequence. For example, the multi-case loads are placed on the interface stations TS (of one or more deck levels) in a sorted arrangement (even though the delivery timing is not in sequence) so as to be in an ordered sequence (e.g. at least the case units needed for the ordered sequence are placed on the interface stations TS in a known relationship with the respective interface stations TS) per the load out fill sequence. As will be described below, in one aspect, the lift  150  picks the multi-case loads from the interface stations TS located at one or more deck levels to feed the respective case load stream COS 1 , COS 2 . In one aspect the load out fill sequence of each lift  150 B is consecutive (n) (e.g. such as where a single stream COS 1 , COS 2  forms the load out fill) or a consecutive skip sequence (n+i where i=1 to m and i corresponds to the number of load streams COS 1 , COS 2  integrated to the load out fill) where there are multiple streams COS 1 , COS 2  forming the load out fill. In the latter case, the ordered sequence of each lift interface station TS (or buffer station BS) is matched or related to the ordered sequence of other load streams converging to the load out fill. 
     As an example,  FIG.  6    illustrates a load out fill in which two case load streams COS 1 , COS 2  are integrated to form a load out fill for a customer order. Here at least one of the case load streams COS 1 , COS 2  are related to the predetermined pickface load order sequence for the load out fill. For exemplary purposes, the customer order may require case unit(s)  1 - 8  which are provided by the two lifts  150 B 1 ,  150 B 2 . Here case units  1  and  3  are output by the lift  150 B 1  in case load stream COS 1  while case units  2  and  4  are output to case load stream COS 2  so that the cases arrive at the output station  160 US in an alternating manner defined by the ordered sequence of the fulfillment stream. In accordance with the ordered sequence case loads  7  and  5  are to be delivered to output conveyor  160 CB such that case units are carried and transferred by a common load handling device LHD of lift  150 B 1  from different holding locations of one or more interface station shelves  7000 A- 7000 F in a single pass of the stack of interface stations TS. To efficiently use each lift  150  in the storage and retrieval system  100  the controller, such as control server  120 , determines on which interface stations(s) case units  5 ,  7  are located. The controller sends commands to a lift, such as lift  150 B 1  associated with the interface stations TS where case units  5 ,  7  are located to pick one or more of the outbound case units. 
     In one aspect where the lift  150 B 1  picks case units  5 ,  7  from a common shelf  7000 B of an interface station TS the lift  150 B 1  moves one or more load handling devices LHD, LHD 1 , LHD 2  of the lift (and the pick head  4000 A,  4000 B,  4000 C,  4000 D,  4270  thereon) in the Z direction so that the transfer arm LHDA, LHDB is located substantially at a level of the interface station shelf  7000 B ( FIG.  8   , Block  11000 ). The transfer arm LHDA, LHDB of the one or more load handling devices LHD, LHD 1 , LHD 2  is extended (e.g. extension of a common transfer arm as in  FIG.  5 A  or the substantially simultaneous extension of two transfer arms as in  FIGS.  5 C and  5 D ) in the Y direction so that the fingers  4273  are disposed between the slats  1210 S below the case units  5 ,  7  ( FIG.  8   , Block  11010 ). The lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the fingers  4273  pass through the slats  1210 S to lift/pick the case units  5 ,  7  from the interface station shelf  7000 B ( FIG.  8   , Block  11020 ). The transfer arm LHDA, LHDB is retracted in the Y direction so as to place the case units  5 ,  7  within a transfer column TC (e.g. an area of open space in which the load handling device travels along the Z direction free from interference from the interface stations and outbound conveyors) of the lift  150 B 1  ( FIG.  8   , Block  11030 ). The lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the transfer arm LHDA, LHDB is located substantially at a level of an interface station  160 TS of the conveyor  160 CB ( FIG.  8   , Block  11040 ). The transfer arm LHDA, LHDB of the one or more load handling devices LHD, LHD 1 , LHD 2  is extended in the Y direction so as to place the case units  5 ,  7  substantially above the interface station  160 TS ( FIG.  8   , Block  11050 ) and the lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the fingers  4273  pass through the slats of the interface station  160 TS (in a manner similar to that illustrated in  FIG.  5 B ) to lower/place the case units  5 ,  7  on a shelf of the interface station  160 TS ( FIG.  8   , Block  11060 ). The transfer arm LHDA, LHDB is retracted in the Y direction so as to place the transfer arm LHDA, LHDB within the transfer column TC of the lift  150 B 1  ( FIG.  8   , Block  11070 ). Here case units carried at all load stations LST 1 -LST 3  (e.g. case unit holding locations) of a common platform PFM (e.g. as in  FIG.  5 A  and as in  FIGS.  5 C,  5 D  where the simultaneous extension/retraction of transfer arms LHDA, LHDB effects a common platform) are picked, transferred and placed in unison with the lift platform at a common elevation. Case units  6 ,  8  are transferred to the outbound conveyors  160 CB by the lift  150 B 1  in a manner substantially similar to that described above with respect to the transfer of case units  5 ,  7  by lift  150 B 1 . As may be realized, the load fill formed by the case load streams COS 1 , COS 2  include mixed case pickfaces arranged in a predetermined pickface load order sequence. In one aspect, the ordered sequence of streaming pickfaces  1 ,  3 ,  5 ,  7  (e.g. case load stream COS 1 ) is combined with a pickface  2 ,  4 ,  6 ,  8  from the other case load stream COS 2  to fill the load fill in the predetermined pickface load order sequence  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 . In one aspect, at least one pickface from the other case load stream COS 2  in combination with the ordered sequence of streaming pickfaces from the case load stream COS 1  forms a portion of consecutive ordered pickfaces (e.g. pickfaces  1 ,  2 ,  3 ,  4 , . . . as shown in  FIG.  6   ) of the predetermined pickface load order sequence. 
     In one aspect, as noted above, the lift  150  sorts the multi-load cases when picking the multi-load cases from interface stations TS located as different deck levels where the sorting sequence corresponds to the ordered sequence of streaming pickfaces (e.g. case load streams COS 1 , COS 2 ). For example, a multiple transfer arm load handling device LHD as in  FIG.  5 C  (and also the individually operable load handling devices LHD 1 , LHD 2  of  FIG.  5 D ) picks and places case units from more than one interface station TS at different storage levels  130 LA,  130 LB and transfers the case units to the same or different outbound conveyor transfer stations TS (e.g. such as when the transfer stations TS of one or more the outbound conveyors serving a common lift  150  are stacked one above the other). For exemplary purposes only, a customer order may require case units  5 ,  7  to be delivered to conveyor  160 CB. Again, to efficiently use each lift  150  in the storage and retrieval system  100  the controller, such as control server  120 , determines on which interface stations(s) case units  5 ,  7  are located. The controller sends commands to a lift, such as lift  150 B 1  associated with the interface stations TS where case units  5 ,  7  are located to pick one or more of the outbound case units in a single pass of the load handling device LHD. Here, case units  5 ,  7  are located on different shelves  7000 A- 7000 F of different interface stations TS such that the lift  150 B 1  moves one or more load handling devices LHD, LHD 1 , LHD 2  of the lift (and the pick head  4000 A,  4000 B,  4000 C,  4000 D,  4270  thereon) in the Z direction so that the transfer arm LHDA, LHDB is located substantially at a level  130 LA,  130 LB of one of the interface station shelves  7000 B,  7000 D ( FIG.  9   , Block  12000 ). The transfer arm LHDA, LHDB of the one or more load handling devices LHD, LHD 1 , LHD 2  is extended in the Y direction so that the fingers  4273  are disposed between the slats  1210 S below one of the case units  5 ,  7  ( FIG.  9   , Block  12010 ) such as case unit  7  when case unit  7  is being picked on an upstroke of the lift  150 B before picking case unit  5  or case unit  5  when case unit  5  is being picked on a down stroke of the lift  150 B before picking case unit  7 . The lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the fingers  4273  pass through the slats  1210 S to lift/pick one of the case units  5 ,  7  (which is some aspects may be a pickface including more than one case unit) from the interface station shelf  7000 B ( FIG.  9   , Block  12020 ). The transfer arm LHDA, LHDB is retracted in the Y direction so as to place the case units  5 ,  7  within a transfer column TC (e.g. an area of open space in which the load handling device travels along the Z direction free from interference from the interface stations and outbound conveyors) of the lift  150 B 1  ( FIG.  9   , Block  12030 ). The lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the transfer arm LHDA, LHDB is located substantially at a level of interface station shelf  7000 A,  7000 B where the other case unit  5 ,  7  is located ( FIG.  9   , Block  12035 ) for picking the other case unit in the manner described above ( FIG.  9   , Blocks  12010 ,  12020 ,  12030 ). The lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the transfer arm LHDA, LHDB is located substantially at a level of an interface station  160 TS of the conveyor  160 CB ( FIG.  9   , Block  12035 ). The transfer arm LHDA, LHDB of the one or more load handling devices LHD, LHD 1 , LHD 2  is extended in the Y direction so as to place the case units  5 ,  7  substantially above the interface station  160 TS ( FIG.  9   , Block  12050 ) and the lift  150 B 1  moves the one or more load handling devices LHD, LHD 1 , LHD 2  in the Z direction so that the fingers  4273  pass through the slats of the interface station  160 TS (in a manner similar to that illustrated in  FIG.  5 B ) to lower/place the case units  5 ,  7  on a shelf of the interface station  160 TS ( FIG.  9   , Block  12060 ). In one aspect the case units  5 ,  7  are placed on the interface station  160 TS substantially simultaneously as a unit while in other aspects the case units  5 ,  7  are placed on the interface station  160 TS sequentially at different times, such as one after another and/or placed to different outbound conveyors interface stations  160 TS (e.g. such as when the transfer stations TS of one or more the outbound conveyors serving a common lift  150  are stacked one above the other) according to a predetermined order out sequence for building the mixed pallet MPL ( FIG.  2   ). The transfer arm LHDA, LHDB is retracted in the Y direction so as to place the transfer arm LHDA, LHDB within the transfer column TC of the lift  150 B 1  ( FIG.  9   , Block  12070 ). 
     In one aspect a common load handling device LHD, LHD 1 , LHD 2  is configured to pick/place one or more case units from multiple interface station TS shelves with a common transfer arm where the case units are sorted on the fly (e.g. during transport on the lift) and/or justified on the load handling device LHD, LHD 1 , LHD 2 . For example, the outbound case units  5 ,  7  are located on interface station shelves  7000 B,  7000 D of different storage levels  130 LA,  130 LB. Again, to efficiently use each lift  150  in the storage and retrieval system  100  the controller, such as control server  120 , determines on which interface stations(s) case units  5 ,  7  are located. The controller sends commands to a lift, such as lift  150 B 1  associated with the interface stations TS where case units  5 ,  7  are located to pick one or more of the outbound case units in a single pass of the load handling device LHD. Here For example, referring to  FIGS.  6 ,  7  and  7 A- 7 E  the load handling device LHD, LHD 1 , LHD 2  of lift  150 B 1  picks case unit  7  (which may be a pickface of more than one case unit) from interface station shelf  7000 B in the manner described above ( FIG.  10   , Block  13000 ). The case unit(s)  7  is justified on the load handling device towards the rear of the payload section  4110 PL as will be described in greater detail below ( FIG.  10   , Block  13005 ). The load handling device LHD, LHD 1 , LHD 2  continues to travel along the mast  4002  in a common pass of the vertical stack of interface stations TS and picks case unit  5  from a different interface station shelf  7000 D with the common transfer arm LHDA so that both case unit(s)  7 ,  5  are located adjacent one another on the common transfer arm LHDA ( FIG.  10   , Block  13010 ). As may be realized, in one aspect, the controller  120  is configured to effect picking of the case unit(s)  5 ,  7  in any suitable order such as, for example, an order that is opposite an order in which the case unit(s) are placed at the interface station  160 TS of the conveyor  160 CB according to the predetermined order out sequence for forming the mixed pallet MPL. 
     Here the load handling device LHD, LHD 1 , LHD 2  grips both case units  7 ,  5  within the payload section  4110 PL in the manner described below ( FIG.  10   , Block  13020 ). The load handling device LHD, LHD 1 , LHD 2  travels along the mast  4002  and interfaces with one or more output lifts  150 B 1  ( FIG.  10   , Block  13030 ). The load handling device LHD,  1 HD 1 , LHD 2  separates the case units  7 ,  5  within the payload section  4110 PL, as will be described in greater detail below, so that case unit(s) are separated in any suitable manner such as, for example, so that case unit(s)  5  is justified towards the front of the payload section  4110 PL and case unit(s)  7  is justified towards the back of the payload section  4110 PL ( FIG.  10   , Block  13040 ). At least the case unit  5  is transferred to the interface station  160 TS ( FIG.  10   , Block  13050 ). The load handling device LHAD, LHD 1 , LHD 2  retracts the transfer arm LHDA, LHDB to return the case unit(s)  7  to the payload section  4110 PL ( FIG.  10   , Block  13060 ) and grips the case unit  7  ( FIG.  10   , Block  13020 ). The case unit(s)  7  is transported to another interface station  160 TSA of output lift  150 B 1  (or placed at the same interface station  160 TS sequentially after placement of case unit(s)  5  at interface station  160 TS) ( FIG.  10   , Block  13030 ), justified toward the front of the payload section  4110 PL ( FIG.  10   , Block  13040 ), and transferred to interface station  160 TS,  160 TSA, as described above ( FIG.  10   , Block  13050 ). In other aspects, depending on the predetermined case unit output sequence, the load handling device LHD, LHD 1 , LHD 2  places both case unit(s)  7 ,  5  at a common location/position, such as simultaneously at a single interface station of lifts  150 B 1 . 
     As noted above, because the pusher bar  4110 PR is a separate, standalone axis of the load handling device LHD, LHD 1 , LHD 2  that operates free of interference from the pick head  4270  extension and lift axes, the pusher bar  4110 PR can be operated substantially simultaneously with the lifting and/or extension of the transfer arm LHDA, LHDB. The combined axis moves (e.g. the simultaneous movement of the pusher bar  4110 PR with the transfer arm LHDA, LHDB extension and/or lift axes) provides for increased payload handling throughput and effects the ordered (e.g. according to the predetermined load out sequence) multi-pick of two or more case units from one or more interface station shelves  7000 A- 7000 F, in one common pass of the vertical stack of interface stations TS. For example, referring again to  FIGS.  7 - 7 E  during a transfer arm LHDA, LHDB multi-pick/place sequence the pusher bar  4110 PR is prepositioned (as the case unit(s) and/or pickface are being picked and transferred into the payload section  4110 PL) to a location that is a predetermined distance X 2  away from the contact depth X 3  (e.g. the depth of the tines occupied by the case unit(s) and/or pickface  7  when being picked/placed from interface station shelf  7000 D or other case unit holding location) ( FIG.  11   , Block  1100 ). The distance X 2  is a minimized distance that only allows sufficient clearance between pusher bar  110 PR and the case unit(s) to allow the case unit(s) to be seated on the rollers  4110 RL. As the case unit(s)  7  are lowered onto the rollers  4110 RL ( FIG.  11   , Block  1110 ) the distance travelled by the pusher bar  4110 PR to contact the case unit(s)  7  is a shorter distance X 2  when compared to moving from a back side  4402  (relative to the Y direction and an access side  4401  of the payload section  4110 PL) of the payload section  4110 PL a distance X 4  as with conventional transport vehicles. When the case unit(s)  7  are lowered by the transfer arm LHDA, LHDB and transferred to the rollers  4110 RL so as to be solely supported by the rollers  4110 RL, the pusher bar  4110 PR is actuated to forward (relative to the lateral direction and an access side  4401  of the payload section  110 PL) justify the case unit(s)  7  ( FIG.  11   , Block  1120 ). For example, the pusher bar  4110 PB may push the case unit(s)  7  in the Y direction so that the case unit(s) contact the fence  4110 PF (which is located at the access side  4401  of the payload section  4110 PL) so that a case unit reference datum may be formed through contact between the case unit(s)  7  and the fence  4110 PF. In one aspect the pusher bar  4110 PR may engage or otherwise grip the case unit(s)  7  during transport of the case units (e.g. so as to hold the case unit(s) against the fence  4110 PF) for maintaining the case unit(s)  7  in a predetermined spatial relationship with each other and the reference frame REFL ( FIG.  5 E ) of the load handling device LHD, LHD 1 , LHD 2  ( FIG.  11   , Block  1130 ). When placing the case unit(s) the pusher bar  4110 PR, after justifying the case unit(s)  7  against the fence  4110 PF, is withdrawn (e.g. in the Y direction) from contact with the case unit(s)  7  ( FIG.  11   , Block  1140 ). Substantially immediately after the pusher bar  4110 PR disengages the case unit(s)  7  one or more of the lift axis (e.g. in the Z direction) and extension axis (e.g. in the Y direction) of the transfer arm LHDA, LHDB are actuated substantially simultaneously with the withdrawing movement of the pusher bar  4110 PR ( FIG.  11   , Block  1150 ). In one aspect both the lift and extension axes are actuated when the pusher bar is withdrawn from contact with the case unit(s)  7  while in other aspect one of the lift and extension axes is actuated. As may be realized, the simultaneous movement of the transfer arm  4110 PA lift axis and/or extension axis with the withdrawal of the pusher bar  4110 PR as well as the decreased distance the pusher moves to justify the case unit(s)  7  decreases the time needed to transfer case unit(s)  7  (e.g. that are sorted on the load handling device LHD, LHD 1 , LHD 2 ) to and from the load handling device and increases throughput of the storage and retrieval system  100 . 
     In another aspect of the disclosed embodiment, as may be realized, in the multi-pick/place sequence multiple case units are substantially simultaneously carried and manipulated within the payload section  4110 PL to further increase throughput of the storage and retrieval system  100  and to effect the multi-pick/place sequence in accordance with a predetermined order out sequence. Referring also to  FIG.  1   , the lift  150 B receives pick and place commands from, for example, control server  120  (and/or warehouse management system  2500 ) and executes those commands (e.g. under the control of control server  120  (or a lift controller) for forming the ordered multi-pick. Here the lift moves the load handling device LHD, LHD 1 , LHD 2  in the Z-direction to pick two or more case units according to the predetermined order out sequence ( FIG.  12   , Block  1201 A). In one aspect the manipulation of the case units  7 ,  5  is a sorting of the case units (in other words picking and placing of case units according to the predetermined load out sequence) where the cases are positioned on the transfer arm LHDA, LHDB for picking/placement of the case units and/or positioned so that the case units are not transferred and remain on the transfer arm LHDA, LHDB while other case units are transferred to and from the transfer arm LHDA, LHDB. Here, the load handling device LHD, LHD 1 , LHD 2  travels in the Z direction and stops at a predetermined shelf  7000 A- 7000 F of an interface station TS, according to the predetermined order out sequence, where the load handling device LHD, LHD 1 , LHD 2  picks one or more case units from the predetermined shelf  7000 A- 700 F of the interface station TS with a common transfer arm LHDA, LHDB where placement of the case units on the common transfer arm LHDA, LHDB corresponds to the predetermined order out sequence as will be described in greater detail below (e.g. the case units are sorted on-the-fly, e.g. during transport, with the lift  150 ). 
     As an example of case manipulation on the bot  110 , still referring to  FIGS.  5 E,  7 ,  7 A- 7 E , case unit(s)  7  may be picked from a case unit holding location (e.g. such as interface station shelf  7000 D for effecting the ordered multi-pick ( FIG.  12   , Block  1201 B). As the case unit(s)  7  is being transferred into the payload section  4110 PL the pusher bar  4110 PR may be pre-positioned ( FIG.  12   , Block  1204 ) adjacent the fence  4110 PF so that the pusher bar  4110 PR is positioned between the case unit(s)  7  and the fence  4110 PF when the case unit(s)  7  is lowered for transfer to the rollers  4110 RL ( FIG.  12   , Block  1205 ). The pusher bar  4110 PR is actuated to push the case unit(s)  7  (resting on the rollers  4110 RL) in the Y direction towards the back (e.g. rear)  4402  of the payload section  4110 PL so that the case unit(s)  7  contacts a justification surface  4273 JS ( FIG.  7   ) of the tines  4273 A- 4273 E and is justified to the back  4402  of the payload section  4110 PL ( FIG.  12   , Block  1210 ). 
     In one aspect, the load handling device LHD, LHDA, LHD 2  continues to traverse mast  4002  in the same direction (e.g. so that all of the case units in the ordered multi-pick are picked in the common pass of the vertical stack of interface stations TS with the load handling device LHD, LHD 1 , LHD 2  travelling in a single direction) and stops at another different predetermined shelf  7000 A- 7000 F of a different interface station TS according to the predetermined order out sequence. As noted above, the pusher bar  4110 PR remains in contact with (e.g. grips) the case unit(s)  7  during transport of the case unit(s) between interface station shelves  7000 A- 7000 F so that the case unit(s)  7  remains in a predetermined location at the back  4402  of the payload section  4110 PL (and/or at a predetermined location in the X direction) relative to the reference frame REFL of the lift  150 B 1  ( FIG.  12   , Block  1215 ). To pick subsequent case units, from for example, the another interface station shelf  7000 B the pusher bar  4110 PR is moved in the Y direction to disengage the case unit(s)  7  and the lift and extension axes of the transfer arm LHDA, LHDB are actuated to retrieve another case unit(s)  5  from the other interface station shelf  7000 B ( FIG.  12   , Block  1220 ). While the case unit(s)  5  are being picked the pusher bar  4110 PR is positioned in the Y direction adjacent the back  4402  of the payload section  4110 PL so as to be located between the case units  7  and the justification surface  4273 JS of the tines  4273 A- 4273 E ( FIG.  12   , Block  1225 ). The case unit(s)  5  are transferred into the payload section and lowered/placed on the rollers  4110 RL (FIG.  12 , Block  1230 ) so that the case units  7 ,  5  are arranged relative to each other along the Y axis. The pusher bar  4110 PR is actuated in the Y direction to push the case units  7 ,  5  towards the fence  4110 PF to forward justify the case units  7 ,  5  ( FIG.  12   , Block  1234 ) and grip/hold the case units  7 ,  5  for transport ( FIG.  12   , Block  1235 ). As may be realized, in one aspect the case units  7 ,  5  are placed at the interface station  160 TS together as a unit while in other aspects the case units  7 ,  5  are sorted, e.g. transported to and placed at different interface stations  160 TS,  160 TSA ( FIG.  12   , Block  1240 ). 
     Where the case units  7 ,  5  are sorted ( FIG.  12   , Block  1250 ) for placement at a common interface station  160 TS,  160 TSA (such as for sequential but chronologically spaced apart, placement of case unit) or at different interface stations  160 TS,  160 TSA, the case units  7 ,  5  are separated from each other in the payload section  4110 PL. For example, the pick head  4270  of the transfer arm LHDA, LHDB may be moved in the Z direction to lift the case units  7 ,  5  from the rollers  4110 RL by an amount sufficient to allow the pusher bar  4110 PR to pass beneath the case unit(s) ( FIG.  13   , Block  1250 A). As the case units  7 ,  5  are lifted the pusher bar  4110 PR is positioned along the Y direction so as to be located between the case units  7 ,  5  (see  FIG.  7 E ) ( FIG.  13   , Block  1250 B). The pick head  4270  is lowered so that the case units  7 ,  5  are transferred to the rollers  4110 RL and so that the pusher bar is inserted between the case units  7 ,  5  ( FIG.  13   , Block  1250 C). The pusher bar  4110 PR is moved in the Y direction (e.g. to separate the case unit(s)) to move case unit(s)  7  towards the back  402  of the payload section  4110 PL (e.g. against the justification surface  4273 JS of the tines  4273 A- 4273 E or any other suitable position) while the case unit(s)  5  remain at the front of the payload section  4110 PL adjacent the fence  4110 PF (e.g. as shown in  FIG.  7 C ) ( FIG.  13   , Block  1250 D). As may be realized, where the case units are held against the justification surface  4273 JS of the tines during transport, the pusher bar is moved in the Y direction (e.g. to separate the case unit(s)) to move case unit(s)  5  towards the front  4401  of the payload section  4110 PL (e.g. against the fence  4110 PF or any other suitable position) while the case unit(s)  7  remain at the back of the payload section  4110 PL adjacent the justification surface  4273 JS. The pusher bar  4110 PR may also be moved in the Y direction to re-justify the case unit(s)  5  against the fence  4110 PF to position the case unit(s) on the tines  4273 A- 4273 E for placement at the interface station  160 TS,  160 TSA ( FIG.  13   , Block  1250 E). As may be realized, with the case unit(s)  7  being positioned substantially against the justification surface  4273 JS of the tines  4273 A- 4273 E (e.g. of the pick head  4270 ) the case unit(s)  5  can be placed at the interface station  160 TS,  160 TSA substantially without interference from the case unit(s)  7  ( FIG.  13   , Block  1250 F), e.g. the case unit  7  is free from contacting case units disposed at the case unit holding location. The case unit(s)  7  is lowered/transferred back into the payload section  4110 PL (e.g. by retracting and lowering the transfer arm  4110 PA) ( FIG.  13   , Block  1250 G). The pusher bar  4110 PR, which is pre-positioned between the justification surface  4273 JS and the case unit(s)  7 , pushes the case unit(s)  7 , which is disposed on the rollers  4110 RL, against the fence  4110 PF to forward justify the case unit(s)  7  for placement at the same or another interface station  160 TS,  160 TSA (e.g. different than the holding location that case unit (s)  5  were placed) ( FIG.  13   , Block  1250 H). The pusher bar  4110 PR remains against the case unit(s)  7  for gripping (e.g. with the fence) the case unit(s) during transport to the other interface station  160 TS,  160 TSA ( FIG.  13   , Block  12501 ). The pusher bar  4110 PR moves away from the case unit(s)  7  and the transfer arm is actuated to lift and extend the pick head  4270  for placing the case unit(s)  7  at the other interface station  160 TS,  160 TSA ( FIG.  13   , Block  1250 J). 
     In one aspect, referring again to  FIG.  5 D , a lift with multiple individually operable load handling devices LHD 1 , LHD 2  picks and places case units from more than one interface station TS at different storage levels  130 LA,  130 LB and transfers the case units to the same or different outbound conveyor interface stations TS (e.g. such as when the transfer stations TS of one or more the outbound conveyors serving a common lift  150  are stacked one above the other). Here, each of the individually operable load handling devices LHD 1 , LHD 2  picks and places case units from the interface station shelves  7000 A- 7000 F and delivers the picked case units to the outbound conveyor  160 CB in a manner substantially similar to the manner described above with respect to  FIGS.  8 ,  9  and  10   . It is noted that in one aspect each load handling device LHD 1 , LHD 2  includes a single transfer arm LHDA, LHDB (see  FIGS.  5 A,  5 D ) or more than one transfer arm LHDA, LHDB (see  FIG.  5 C ) (e.g. one load handling device include a single transfer arm while the other load handling device includes more than one transfer arm; both load handling devices include a single transfer arm; both load handling devices include more than one transfer arm). The load handling devices LHD 1 , LHD 2  in one aspect include the sorting and justification mechanisms described above with respect to  FIG.  5 E . 
     The output lifts  150 B 1 ,  150 B 2  transfer the ordered multi-pick(s) placed on the shelves  7000 A- 7000 L by the bots  110  to the output station  160 UT also in accordance with the predetermined order out sequence. For example, referring again to  FIG.  6   , the pickfaces  1 - 22  are picked by the lifts  150 B 1 ,  150 B 2  in sequenced order so that the pickfaces  1 - 22  are delivered to the output station  160 UT in the predetermined order (indicated by, for example, the number associated with each case unit/pickface illustrated in  FIG.  6   ) needed to form the mixed pallet load MPL ( FIG.  2   ) and/or in the predetermined order sequence (e.g. an order out sequence) of picked items according to, for example, an order, fulfilling one or more customer orders, in which case units CU are sequenced for placement in one or more bag(s), tote(s) or other container(s) TOT at an operator station  160 EP. As such, each of the interface stations TS of each lift  150 B 1 ,  150 B 2  forms a buffer that holds one or more case unit(s) until the case unit(s) are needed and picked by the respective lift  150 B 1 ,  150 B 2  for forming the mixed pallet load. 
     Referring to  FIG.  15   , in accordance with aspects of the disclosed embodiment, storage spaces arrayed on racks along picking aisles are provided ( FIG.  15   , Block  1600 ). Multiple level decks are also provided ( FIG.  15   , Block  1610 ), where at least one deck level of the multiple level decks communicates with each aisle, where the multiple level decks and aisles define a rolling surface for an autonomous transport vehicle at each level of the multiple level decks. Racks at multiple rack levels are accessed from a respective rolling surface that is common to the multiple rack levels ( FIG.  15   , Block  1620 ), where the racks are disposed along at least one aisle at each level of the multiple level decks. In one aspect, a vertical pitch between rack levels varies for a portion of a respective aisle. In one aspect, the vertical pitch between at least two rack levels of the portion of the respective aisle is related to another vertical pitch between at least two other rack levels of another aisle portion of the respective aisle so that the autonomous transport vehicle effects multiple picks in an ordered sequence in a common aisle pass. In one aspect, the vertical pitch between at least two rack levels of the portion of the respective aisle is related to another vertical pitch between at least two other rack levels of another aisle portion of the respective aisle so that the vertical pitch and the other vertical pitch effects substantially filling a vertical space between the multiple deck levels with stored items. 
     In accordance with one or more aspects of the disclosed embodiment, a product order fulfillment system includes multiple decks arrayed at different levels and defining multilevel decks; at least one autonomous transport vehicle disposed on each of the multilevel decks, and configured for holding and transporting a pickface on each deck; at least one lift, traversing and connecting more than one level of the multilevel decks, and arranged for lifting and lowering the pickface from the multilevel decks; and at least one pickface transfer station on each deck interfacing between the autonomous transport vehicle on the deck and the at least one lift to effect transfer of the pickface between the autonomous transport vehicle and the at least one lift; wherein the at least one lift defines a fulfillment stream of mixed case pickfaces outbound from the multilevel decks to a load fill, and at least one stream of the fulfillment stream has an ordered sequence of streaming pickfaces wherein the ordered sequence of streaming pickfaces is based on another fulfilment stream. 
     In accordance with one or more aspects of the disclosed embodiment, the load fill comprises mixed case pickfaces arranged in a predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the ordered sequence of streaming pickfaces from the at least one stream is related to the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the ordered sequence of streaming pickfaces from the at least one stream is combined with a pickface from the other fulfillment stream to fill the load fill in the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, at least one pickface from the other fulfillment stream in combination with the ordered sequence of streaming pickfaces from the at least one stream forms a portion of consecutive ordered pickfaces of the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the at least one lift includes a first lift and the other fulfillment stream is defined by another of the at least one lift independent from the first lift. 
     In accordance with one or more aspects of the disclosed embodiment, the first lift has a lift platform arranged to support more than one pickface on the lift platform and is configured so that the first lift effects picking or placing of the more than one pickface, corresponding to the ordered sequence of streaming pickfaces, with the lift platform at a common lift elevation. 
     In accordance with one or more aspects of the disclosed embodiment, the first lift effects picking or placing of the more than one pickface substantially simultaneously. 
     In accordance with one or more aspects of the disclosed embodiment, the product order fulfillment system further includes a storage array with storage racks having pickface storage locations arranged in multiple levels corresponding to the different levels of the multilevel decks. 
     In accordance with one or more aspects of the disclosed embodiment, a product order fulfillment system includes multiple decks arrayed at different levels and defining multilevel decks; at least one autonomous transport vehicle disposed on each of the multilevel decks, and configured for holding and transporting a pickface on each deck; a first lift, traversing and connecting more than one level of the multilevel decks, and arranged for lifting and lowering the pickface from the multilevel decks; a second lift, traversing and connecting more than one level of the multilevel decks, and arranged for lifting and lowering the pickface from the multilevel decks; and at least one pickface transfer station on each deck interfacing between the autonomous transport vehicle on the deck and the first and second lifts to effect transfer of the pickface between the autonomous transport vehicle and the first and second lifts; wherein the first lift defines a first fulfillment stream of mixed case pickfaces outbound from the multilevel decks to a load fill, the second lift defines a second fulfillment stream of mixed case pickfaces outbound from the multilevel decks to the load fill, and the first fulfillment stream has as first ordered sequence of streaming pickfaces and the second stream has a second ordered sequence of streaming pickfaces, the first ordered sequence of streaming pickfaces complementing the second ordered sequence of streaming pickfaces and being related to a load fill ordered sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the load fill comprises mixed case pickfaces arranged in a predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, at least one of the first ordered sequence of streaming pickfaces from the first fulfillment stream and the second ordered sequence of streaming pickfaces from the second fulfillment stream is related to the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the first ordered sequence of streaming pickfaces from the first fulfillment stream is combined with a pickface from the second ordered sequence of streaming pickfaces from the second fulfillment stream to fill the load fill in the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, at least one pickface from the second fulfillment stream in combination with the first ordered sequence of streaming pickfaces from the first fulfillment stream forms a portion of consecutive ordered pickfaces of the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the at least one lift includes a first lift and the second fulfillment stream is defined by another of the at least one lift independent from the first lift. 
     In accordance with one or more aspects of the disclosed embodiment, the first lift has a lift platform arranged to support more than one pickface on the lift platform and is configured so that the first lift effects picking or placing of the more than one pickface, corresponding to the first ordered sequence of streaming pickfaces, with the lift platform at a common lift elevation. 
     In accordance with one or more aspects of the disclosed embodiment, the first lift effects picking or placing of the more than one pickface substantially simultaneously. 
     In accordance with one or more aspects of the disclosed embodiment, the product order fulfillment system further includes a storage array with storage racks having pickface storage locations arranged in multiple levels corresponding to the different levels of the multilevel decks. 
     In accordance with one or more aspects of the disclosed embodiment, a method for product order fulfillment includes providing multiple decks arrayed at different levels and defining multilevel decks; disposing at least one autonomous transport vehicle on each of the multilevel decks and holding and transporting, with the at least one autonomous transport vehicle, a pickface on each deck; lifting and lowering the pickface from the multilevel decks with at least one lift that traverses and connects more than one level of the multilevel decks; effecting transfer of the pickface between the autonomous transport vehicle and the at least one lift with at least one pickface transfer station on each deck that interfaces between the autonomous transport vehicle on the deck and the at least one lift; and defining, with the at least one lift, a fulfillment stream of mixed case pickfaces outbound from the multilevel decks to a load fill, where at least one stream of the fulfillment stream has an ordered sequence of streaming pickfaces and where the ordered sequence of streaming pickfaces is based on another fulfilment stream. 
     In accordance with one or more aspects of the disclosed embodiment, the load fill comprises mixed case pickfaces, the method further includes arranging the mixed case pickfaces in a predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the ordered sequence of streaming pickfaces from the at least one stream is related to the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the method further includes combining the ordered sequence of streaming pickfaces from the at least one stream with a pickface from the other fulfillment stream to fill the load fill in the predetermined pickface load order sequence. 
     In accordance with one or more aspects of the disclosed embodiment, the method further includes forming a portion of consecutive ordered pickfaces of the predetermined pickface load order sequence with at least one pickface from the other fulfillment stream in combination with the ordered sequence of streaming pickfaces from the at least one stream. 
     In accordance with one or more aspects of the disclosed embodiment, the at least one lift includes a first lift, the method further comprising defining the other fulfillment stream by another of the at least one lift independent from the first lift. 
     In accordance with one or more aspects of the disclosed embodiment, the first lift has a lift platform arranged to support more than one pickface on the lift platform, the method further comprising effecting, with the first lift, picking or placing of the more than one pickface, corresponding to the ordered sequence of streaming pickfaces, with the lift platform at a common lift elevation. 
     In accordance with one or more aspects of the disclosed embodiment, the method further includes effecting, with the first lift, picking or placing of the more than one pickface substantially simultaneously. 
     In accordance with one or more aspects of the disclosed embodiment, the method further includes providing a storage array with storage racks having pickface storage locations arranged in multiple levels corresponding to the different levels of the multilevel decks. 
     In accordance with one or more aspects of the disclosed embodiment, a product order fulfillment system includes multiple decks arrayed at different levels and defining multilevel decks; at least one autonomous transport vehicle disposed on each of the multilevel decks, and configured for holding and transporting a pickface on each deck; at least one lift, traversing and connecting more than one level of the multilevel decks, and arranged for lifting and lowering the pickface from the multilevel decks; and at least one pickface buffer station on each deck interfacing between the at least one autonomous transport vehicle on the deck and the at least one lift to effect transfer of the pickface between the autonomous transport vehicle and the at least one lift; wherein the at least one lift defines a fulfillment stream of mixed case pickfaces streaming outbound from the multilevel decks to a load fill, and wherein the at least one pickface buffer station, of at least one of the multilevel decks, commonly supports more than one of the mixed case pickfaces defining a portion of the streaming pickfaces in an ordered sequence of streaming pickfaces based on a predetermined sequence of the load fill. 
     In accordance with one or more aspects of the disclosed embodiment, the at least one pickface buffer station forms a common pickface transfer interface for the at least one lift, so that the commonly supported pickfaces are picked in common with the at least one lift. 
     In accordance with one or more aspects of the disclosed embodiment, the at least one pickface buffer station on more than one of the multilevel decks each commonly support more than one of the mixed case pickfaces defining a portion of the streaming pickfaces in an ordered sequence of streaming pickfaces based on the predetermined sequence of the load fill. 
     In accordance with one or more aspects of the disclosed embodiment, the mixed case pickfaces defining the portion of the streaming pickfaces in the ordered sequence commonly supported on the buffer station is based on an ordered sequence of pickfaces on another buffer station of another fulfillment stream. 
     In accordance with one or more aspects of the disclosed embodiment, the product order fulfillment system further includes a controller in communication with the at least one autonomous transport vehicle, the controller being configured to effect placement of pickfaces on the at least one pickface buffer station based on the ordered sequence of streaming pickfaces. 
     It should be understood that the foregoing description is only illustrative of the aspects of the disclosed embodiment. Various alternatives and modifications can be devised by those skilled in the art without departing from the aspects of the disclosed embodiment. Accordingly, the aspects of the disclosed embodiment are intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims. Further, the mere fact that different features are recited in mutually different dependent or independent claims does not indicate that a combination of these features cannot be advantageously used, such a combination remaining within the scope of the aspects of the invention.