A grid framework structure

Abstract

A grid framework structure 80 for supporting one or more robotic load handling devices (Fig 5) operative thereon, comprises a supporting framework structure 82 with a plurality of prefabricated frames

Description

Field of Invention The present invention relates to the field of remotely operated load handling devices on tracks located on a grid framework structure for handling storage containers or bins stacked in tire 5 grid framework structure, more specifically to a grid framework structure for supporting remotely operated load handling devices. Background Storage and retrieval systems 1 comprising a three-dimensional storage grid framework 10 structure, within which storage containers / bins / totes are stacked on top of each other, are well known. PCT Publication No. WO2015 / 185628A (Ocado) describes a known storage and fulfilment or distribution system in which stacks of bins or containers are arranged within a grid framework structure. Tire bins or containers are accessed by load handling devices remotely operative on tracks located on the top of the grid framework structure. A system of 15 this type is illustrated schematically in Figures 1 to 3 of the accompanying drawings. As shown in Figures 1 and 2, stackable containers, known as storage bins or containers 10, are stacked on top of one another to form stacks 12. The stacks 12 are arranged in a grid framework structure 14 in a warehousing or manufacturing environment. The grid framework structure is made up of a plurality of storage columns or grid columns. Figure 1 is a schematic perspective 20 view of the grid framework structure 14, and Figure 2 is a top-down view showing a stack 12 of bins 10 arranged within the grid framework structure 14. Each bin 10 typically holds a plurality of product items (not shown), and the product items within a bin 10 may be identical, or may be of different product types depending on the application. In detail, the grid framework structure 14 comprises a plurality of vertical uprights or upright 25 members or upright columns 16 that support horizontal grid members 18, 20. A first set of parallel horizontal grid members 18 is arranged perpendicularly to a second set of parallel horizontal grid members 20 to form a track sy stem or grid structure or grid 15 comprising a plurality of grid cells 17. Each grid cell in the grid framework structure has at least one grid column for storage of a stack of containers. For the avoidance of doubt, the term “grid 30 framework structure" is used to mean a three-dimensional structure within which the storage containers are stored, and the terms “track system”, “grid structure” and “grid” are used interchangeably to mean the two-dimensional structure in a substantially horizontal plane upon which the load handling devices operate. The grid cell has an opening to allow a load handling device to lift a container or storage bin through the grid cell. In the track system, the first set of parallel horizontal grid members 18 intersect the second set of parallel horizontal grid members 5 at nodes. Tire track system is supported by the upright members 16 at each of the nodes or at the point where the grid members intersect such that the upright members are interconnected at their tops ends by the intersecting grid members. The grid members 16, 18, 20 are typically manufactured from metal and typically welded or bolted together or a combination of both. The storage bins or containers 10 are stacked between the upright members 16 of the grid 10 framework structure 14, so that the upright members 16 guard against horizontal movement of the stacks 12 of bins 10, and guide vertical movement of the storage bins 10. The top level of the grid framework structure 14 includes rails or tracks 22 arranged in a grid pattern across the top of the stacks 12 to define a track system. Referring additionally to Figure 3, the rails 22 support a plurality of load handling devices 30. The track system comprises a 15 first set 22a of parallel rails 22 to guide movement of the robotic load handling devices 30 in a first direction (for example, an X-direction) across the top of the grid framework structure 14, and a second set 22b of parallel rails 22, arranged perpendicular to the first set 22a, to guide movement of the load handling devices 30 in a second direction (for example, a Y-direction), perpendicular to the first direction. In this way, the rails 22 allow movement of the robotic load 20 handling devices 30 laterally in two dimensions in the horizontal X-Y plane, so that a load handling device 30 can be moved into position above any of the stacks 12. For the purpose of definition of the present invention, the term “robotic” load handling device and load handling device are used interchangeably in the description to mean the same device. The track or rail can be a separate component to the grid member (sometime referred to as a 25 ‘track support’) or alternatively, the track is integrated into the grid member as a single body, i.e. forms part of the grid member. For example, each of the first and second sets of horizontal grid members 18, 20 of the track system can function as a track support structure and the first and second sets of tracks of the track system can be mounted to the track support structure for guiding the load handling devices in two dimensions on the track system. 30 A known load handling device otherwise known as a bot 30 shown in Figure 4 and 5 comprising a vehicle body 32 is described in PCT Patent Publication No. WO2015 / 019055 (Ocado), hereby incorporated by reference, where each load handling device 30 only covers a single grid space or grid cell of the grid framework structure 14. Here, the load handling device 30 comprises a wheel assembly comprising a first set of wheels 34 consisting of a pair of wheels on the front of the vehicle body 32 and a pair of wheels 34 on the back of the vehicle 32 for engaging with the first set of rails or tracks to guide movement of the device in a first direction, and a second 5 set of wheels 36 consisting of a pair of wheels 36 on each side of the vehicle 32 for engaging with the second set of rails or tracks to guide movement of the device in a second direction. Each of the sets of wheels are driven to enable movement of the vehicle in X and Y directions respectively along the rails. One or both sets of wheels can be moved vertically to lift each set of wheels clear of the respective rails, thereby allowing the vehicle to move in the desired 10 direction, e.g. X or Y direction on the track system. The load handling device 30 is equipped with a lifting device or crane mechanism to lift a storage container from above. The crane mechanism comprises a winch tether or cable 38 wound on a spool or reel (not shown) and a grabber device 39 in the form of a lifting frame. The lifting device comprises a set of lifting tethers 38 extending in a vertical direction and 15 connected nearby or at the four comers of the lifting frame 39, otherwise known as the grabber device (one tether near each of the four comers of the grabber device) for releasable connection to a storage container 10. The grabber device 39 is configured to releasably grip the top of a storage container 10 to lift it from a stack of containers in a storage system of the type shown in Figure 1 and 2. 20 The wheels 34, 36 are arranged around the periphery of a cavity or recess, known as a container-receiving recess or container receiving space 40, in the lower part. The recess is sized to accommodate the container 10 when it is lifted by the crane mechanism, as shown in Figure 5 (a and b). When in the recess, the container is lifted clear of the rails beneath, so that the vehicle can move laterally to a different location. On reaching the target location, for example 25 another stack, an access point in the storage system or a conveyor belt, the bin or container can be lowered from the container receiving portion and released from the grabber device. The container receiving space may comprise a cavity or recess arranged within the vehicle body, e.g. as described in WO 2015 / 019055 (Ocado Innovation Limited). Alternatively, the vehicle body of the load handling device may comprise a cantilever as taught in WO2019 / 238702 30 (Autostore Technology AS) in which case the container receiving space is located below a cantilever of the load handing device. In this case, the grabber device is hoisted by a cantilever such that the grabber device is able to engage and lift a container from a stack into a container receiving space below the cantilever. To ensure stability of the grid framework structure, prior art storage systems are largely dependent on various supports and bracing arranged within or at least partly along the periphery of the grid framework structure. However, the use of various supports and bracing (antimovement braces) to stabilise the grid framework structure from internal and external forces is 5 disadvantageous for a number of reasons. The grid framework structure occupies space or area which could be utilised to store containers, in that it prevents optimum usage of available space or area for the storage of containers. The need of a supporting structure may limit the available options for positioning of the grid framework structure since any auxiliary grid supporting structure often requires connection to a surrounding structure such as the inner walls of a 10 building. The requirement of a supporting structure to stabilise the grid framework structure is generally not cost efficient and occupies useful storage space. WO2019 / 101367 (Autostore Technology AS) teaches a free-standing storage grid requiring a less extensive auxiliary grid supporting structure by integrating a grid supporting structure in the storage grid structure. The grid supporting structure is made up of four storage columns 15 interconnected by multiple vertically inclined support struts. The storage column profiles have a cross-section comprising a hollow centre section and four comer sections, each comer section comprising two perpendicular bin guiding plates for accommodating a comer of a storage bin. The support struts have a width which allows them to fit in between two parallel guiding plates so as to not compromise the ability of the storage columns to accommodate a stack of containers 20 or storage bins. To erect the grid framework structure in the art, a plurality of vertical uprights are individually positioned one piece at a time in a grid-like pattern on the ground. The assembling of individual vertical uprights together one piece at a time is sometimes referred to as “stick-built” structures. The “stick-built” approach of the assembling the grid framework structure requires numerous 25 time-consuming adjustments to be made for reliable operation of the robotic load handling devices on the tracks. The height of the vertical uprights and thus the level of the grid mounted thereon is adjusted by one or more adjustable feet at the base or bottom end of each of the vertical uprights. A sub-group of the vertical uprights are braced together to provide structural stability to the grid framework structure. The vertical uprights are interconnected at their top 30 ends by grid members so that the grid members adopt the same grid pattern as the vertical uprights, i.e. the vertical uprights support the grid members at the point or node where each of the grid members intersect in the grid pattern. For the purpose of explanation of the present invention, the points or junctions where tire grid members intersect or are interconnected constitute the nodes of the track system and correspond to the area where the track system is supported by a vertical upright. The resultant grid framework structure can be considered as a free standing rectilinear assemblage of upright columns supporting the grid formed from intersecting horizontal grid members, i.e. a four wall shaped framework. 5 The arrangement of the vertical uprights provides multiple vertical storage columns for the storage of one or more containers in a stack. Ure vertical uprights help to guide the grabber device of the lifting mechanism as the grabber device engages with a container within the grid framework structure and is lifted towards the load handling device operative on the grid. The size of the gnd framework structure and thus the ability to store containers containing different 10 items or stock keeping units (SKUs) is largely dependent on the number of vertical uprights spanning over a given footprint of the grid framework structure. However, one of the biggest bottlenecks in the building of a fulfilment or distribution centre is the erection of the grid framework structure. The time and cost to assemble the grid framework structure represents a huge proportion of the time and cost to build a fulfilment or distribution centre. The biggest 15 and the most time consuming operation involves erecting the vertical uprights individually and fixing the track system to the vertical uprights. WO2019 / 157197 (Alert Innovation Inc.) attempts to address this problem by providing an automated fulfilment system comprising a plurality of storage modules, wherein each storage module of the plurality of storage modules comprises a pair of shelf modules comprising a 20 number of defined storage locations for storing containers otherwise known as totes. The pair of shelf modules are spaced apart from each other so as to allow a mobile robot to pass between the pair of shelf modules and retrieve or deliver inventory to storage locations. However, the automated storage system taught in WO2019 / 157197 (Alert Innovation Inc.) does not provide a dense storage system as taught in WO2015 / 185628A (Ocado) since the shelf modules take 25 up valuable storage space. WO2020 / 074242 (Autostore Tech) teaches a plurality of mobile containers, each container having an automated storage and retrieval system comprising a grid framework structure for storing storage bins (wherein the bins may contain items). One of the mobile containers may be a so-called master container having storage columns and dedicated columns for receiving 30 storage bins from an access station and delivering storage bins to an access station. The remaining mobile containers may be so-called supply containers comprising an automated storage and retrieval system without dedicated columns for receiving storage bins from the access station and delivering storage bins to the access station. Within the system, the master container may be connected to at least one supply container such that a bin handling vehicle can move from the storage grid structure of the master container to a storage grid structure of the supply container. Ilie master container and / or supply container may be connected to a 5 plurality of supply containers, which again can be connected to a plurality of supply containers and so on. A pivotable intermediate element is used to connect the respective rail system of automated storage and retrieval systems of adjacent mobile containers. A grid framework structure is thus required that allows the grid framework structure to be erected quicker and / or cheaper than current grid framework structures in the art. Moreover, the 10 grid framework structure should also maximise the available space or area for the storage of multiple containers. Summary of Invention The present applicant has mitigated the above problem by forming the grid framework structure 15 from fewer structural components than is currently practised as described above, yet still maintaining tire same structural integrity as the existing grid framework structure for bearing the weight of one or more robotic load handling devices (which can weigh as much as 150kg) operative on the grid framework structure. The present invention provides a grid framework structure assembled from a plurality of modular storage units, each of the plurality of modular 20 storage units providing storage for a plurality of stacks of storage containers. Whilst WO2020 / 074242 (Autostore Tech) provides a mobile storage system that enables multiple automated storage and retrieval systems in mobile containers to be connected together in a side-by-side relationship to increase the storage capacity of the mobile storage system, no provisions are made to take into account the effects of thermal expansion of the grid framework structure 25 in one or more of the mobile storage units when assembled together resulting in movement and / or distortion of the rail system. Increasing the storage capacity of the automated storage and retrieval system by extending the grid framework structure through assembling multiple modular storage units together runs the risk that thermal expansion of the grid framework structure within one of the mobile storage units may generate sufficient forces to have a knock-30 on effect on the grid framework structure of an adjacent modular storage unit. For example, forces generated as a result of thermal expansion within a grid framework structure of a mobile storage unit may be transferred to adjacent mobile storage units. The cumulative effect of such forces across multiple modular storage units may cause different areas of the grid framework structure to buckle or at least distort. At a granular level, thermal expansion of one or more tracks may also cause one or more vertical members interconnected by the tracks at their upper ends to distort. As the vertical uprights are arranged to provide storage columns in the grid 5 framework structure, distortion in one or more of the vertical uprights may cause the grabber device and / or storage container to foul the vertical uprights as it is guided vertically by the vertical uprights. The term vertical member and vertical upright are used interchangeably in the description to mean the same feature. Whilst WO2020 / 074242 (Autostore Tech) attempts to provide a grid framework structure that 10 can be easily transported and erected in a remote location, the grid framework structure in each of the mobile containers still suffers from the problem of the need to assemble the grid framework by the “stick-built” approach discussed above and therefore, suffers from the problems associated with long build time and material costs. In contrast to the ’’stick-built” approach of the assembling the grid framework structure 15 requiring numerous time-consuming adjustments to be made to the level of the rail or track system for reliable operation of the robotic load handling devices on the tracks, tire grid framework structure according to the present invention is erected from a plurality of prefabricated panels or frames, wherein each of the plurality of the prefabricated panels or frames is assembled from a sub-group of the vertical members braced together by one or more 20 bracing members. For the purpose of definition, the term “prefabricated” in the context of the grid framework structure build is construed to cover pre-assembling or manufacturing sections of the grid framework structure prior to assembly of the grid framework structure on site so that the grid framework structure can be assembled at a different location to the manufacture of the prefabricated sections of the grid framework structure, wherein each of the prefabricated 25 sections comprises a plurality of the parts or components of the grid framework structure. The different location can be a location remote from where the grid framework structure is assembled, i.e. in another building, or alternatively, assembled in the same location but in a different area of the same location, e.g. into a different area of the same building. In the context of the term “panels”, the prefabricated panels are formed from bracing together a sub-group of 30 the vertical members in a single plane, e.g. in a single vertical plane. Preferably, the bracing member is a horizontal bracing member. The prefabricated panels or frames are assembled together in a three dimensional grid pattern to form a plurality of modular storage cells, where each of the modular storage cells is sized to store a plurality of stacks of storage containers, i.e. each of the modular storage cells adopts an open storage space for the storage of a plurality of stacks of storage containers. The 5 prefabricated modular panels are load bearing in the sense that when assembled together to form the supporting framework structure, they provide a load bearing structure to support one or more load handling devices moving on the track system mounted to the supporting framework structure. Having each of the prefabricated modular panels extend in a single plane also facilitates the ability to flat pack the supporting framework structure for transport. The 10 prefabrication of the modular panels permits quick assembly of the supporting framework structure at a site or within a building. This has the advantage that the supporting framework structure can be constructed in existing vacant buildings or warehouses. To mitigate the effects of thermal expansion of the prefabricated frames in a single modular storage cell impacting an adjacent modular storage cell in the grid framework structure, the 15 arrangement of tire prefabricated frames in each of the modular storage cells in the grid framework structure can function as standalone modular units that are sufficiently spaced apart to not impact an adjacent modular storage cell in the assembly. Thus, forces generated as a result of thermal expansion effects in a single modular storage cell is prevented from impacting the geometry of an adjacent modular storage cell. As each of the individual modular storage 20 cells is assembled from a plurality of prefabricated panels, the spacing between adjacent modular storage cells is such so as to allow components of the prefabricated panels to elastically deform in the spacing but not exceed the spacing to cause plastic deformation. One of the main consequences of the thermal expansion effects of the grid framework structure is the distortion of the tracks on which the robotic load handling device runs, as the distortion 25 will prevent the robotic load handling device from properly moving on the grid framework structure since the wheels of the load handling device are constrained within the tracks of the track system. To cater for the effects of thermal expansion of the assembly of modular storage cells, the present invention provides a grid framework structure for supporting one or more robotic load 30 handling devices operative on the grid framework structure, the grid framework structure comprising: i) a supporting framework structure comprising a plurality of prefabricated frames comprising a first set of parallel prefabricated frames extending in a first direction and the second set of parallel prefabricated frames extending in a second direction, the second direction being substantially perpendicular to the first direction such that the plurality of the prefabricated frames are arranged in a three dimensional grid pattern comprising a plurality of modular 5 storage cells for the storage of a plurality’ of stacks of containers; wherein adjacent modular storage cells share a common prefabricated frame, each of the plurality of prefabricated frames lying in a vertical plane and comprising a plurality of vertical members braced together by a bracing member, the supporting framework structure is arranged such that one or more vertical members of adjacent prefabricated frames are connected together by one or more fasteners at 10 the interface between adjacent modular storage cells; ii) a track system for guiding movement of the one or more robotic load handling devices on the grid framework structure, the track system being mounted to the supporting framework structure and comprising a plurality of tracks arranged in a grid pattern comprising a plurality of grid cells extending across the plurality of modular storage cells such that each of the 15 plurality of modular storage cells is configured to support a sub-group of two or more grid cells of the track system; wherein the track system further comprises a track support structure comprising a plurality of track supports arranged in a grid pattern corresponding to the grid pattern of the track system, the plurality of track supports being interconnected at the intersections of the plurality of track 20 supports in the grid pattern, the track support structure is sub-divided into a plurality of modular sub-frames such that each of the plurality of modular sub-frames comprises the subgroup of two or more grid cells of the track system, the interconnections of the plurality of track supports at the interface between the adjacent modular storage cells comprise one or more slip joints such that adjacent modular sub-frames 25 are moveable relative to each other along a substantially horizontal plane via the one or more slip joints; wherein one or more spacers are disposed between the adjacent vertical members at the interface between adjacent modular storage cells; each of the one or more spacers comprises a first spacing member and a second spacing member, the first spacing member being configured 30 to space adjacent vertical members connected in the first direction by a first spacing and the second spacing member being configured to space adjacent vertical members connected in the second direction by a second spacing. For the purpose of definition, the arrangement of the tracks and the track supports in a grid pattern include having a first set of parallel tracks and / or track supports extending in a first direction and a second set of parallel tracks and / or track supports extending in a second direction, the second direction being substantially perpendicular to the first direction. In 5 comparison to the interconnections of the plurality of track supports at the interface between adjacent storage cell, the interconnections at the intersections of the plurality of track supports within a given modular sub-frame are fixedly connected together. For the purpose of definition of the present invention, the term ‘'fixedly” is construed to mean that is there is little or no movement at the intersections of the plurality of track supports relative to each other in excess 10 of 0.5mm. In comparison to the stick build process to erecting the grid framework structure known in the art, the grid framework structure according to the present invention is formed from a plurality of prefabricated panels that are arranged in a grid pattern such that adjacent modular storage cells share a common prefabricated frame. The common prefabricated frame shared between adjacent modular storage cells enables a track system to extend across the 15 plurality of modular storage cells for one or more robotic load handling devices operative on the grid framework structure to move across the plurality of modular storage cells. The plurality of prefabricated frames arranged in a three dimensional grid pattern defines a supporting framework structure for supporting the track system. In addition to the need to assemble the prefabricated frames forming the supporting framework structure faster than the traditional 20 stick build approach, there is also a need to assemble the track system faster. Traditionally, the track system is formed by laying individual track elements in both X and Y Cartesian directions in a horizontal plane and interconnecting the track elements to the upright members where the track elements intersect in the track system by a cap plate (see PCT / EP2021 / 055217 in the name of Ocado Innovation Limited and WO 18146304 in the name of Autostore Tech AS). 25 Laying the individual track elements separately is not only time consuming but cumbersome as the track elements would need to be individually interconnected to the vertical uprights. The track system comprises a track support structure comprising a plurality of track supports arranged in a grid pattern corresponding to the grid pattern of the plurality of tracks. The plurality of track supports are interconnected at the intersections of the plurality of track 30 supports in the grid pattern. To provide a track system that can be installed faster than the traditional method of laying individual track elements, the track support structure is subdivided into a plurality of discrete modular sub-frames. Each of the plurality of modular subframes comprises the sub-group of the two or more grid cells of the track system, e.g. a sub- group of X by Y grid cells of the track system, where X and Y can be any number equal to 2 or greater. The interconnections at the intersections of the plurality of tracks supports within a given modular sub-frame are fixedly connected together. Thus, instead of building up the track system from individual track elements, the track system is assembled from modular sub-5 frames. As each modular sub-frame comprises a sub-group of two or more grid cells of the track system, assembling the modular sub-frames together to form the track system becomes much easier. Each of the modular sub-frames can be sized to occupy a single modular storage cell of the supporting framework structure such that each of the plurality of modular storage cells is configured to support two or more grid cells of the track system. This provides the 10 advantage of prefabricating sections of the track system prior to assembly on the supporting framework structure. For example, sub-dividing the track support structure into a plurality7 of discrete modular sub-frames allows sections of the track system to be hoisted onto the supporting framework structure. The plurality of tracks can be integrated into the track support structure, in which case both the track and the track support can simply be mounted to the 15 supporting framework structure in a single operation. Alternatively, the plurality of tracks can be separately mounted to the track support structure resulting in a double operation involving laying the track support structure to the supporting framework structure and subsequently mounting the tracks to the track support structure. In contrast to the interconnections of the plurality of track supports at the intersections of the 20 plurality of track supports being fixedly connected together (e.g. by a bolt), the interconnections at the interface between the adjacent modular storage cells are moveable via one or more slip or movement joints. Hie one or more slip or movement joints at the interface between adjacent modular storage cells allows for thermal expansion in the track system allowing adjacent modular sub-frames to be moveable relative to each other along a 25 substantially horizontal plane. The one or more slip joints at the interface between adjacent modular storage cells allows for movement in the range 0.5mm to 10mm, preferably in the range 0.5mm to 5mm to accommodate for thermal expansion of the track supports. In other words, the one or more slip joints allows for greater movement between the interconnections of the track supports at the interface between adjacent modular storage cells than the 30 interconnections of the plurality of track supports within a given modular sub-frame. Thus, movement in one modular storage cell as a result of thermal expansion does not greatly affect movement of an adjacent modular structure cell due to movement via the one or more slip joints between adjacent modular storage cells. Optionally, each of the one or more of the slip joints comprises a bracket (e.g. cradle bracket) that is configured to cradle one or more track supports between adjacent modular storage cells such that adjacent modular sub-frames are separable. Alternatively, each of the one or more slip joints can comprise a bridging member comprising a pm and slot arrangement, whereby the pin is moveable in the slot. 5 Considering that the track support structure is sub-divided into a plurality of modular subframes, optionally, the one or more slip joints comprises:- i) a first set of slip joints at the interface between the adjacent modular storage cells in a first direction such that the adjacent modular sub-frames are moveable relative to each other along the substantially horizontal plane in the first direction and; 10 ii) a second set of slip joints at the interface between the adjacent modular storage cells in a second direction such that the adjacent modular sub-frames are moveable relative to each other along the substantially horizontal plane in the second direction, wherein the second direction is substantially perpendicular to the first direction. Having a first and second sets of slip or movement joints allows movement of adjacent modular 15 sub-frames of the track support structure at the interface between adjacent modular storage cells in the first direction and in the second direction. To form a grid framework structure comprising a plurality of standalone modular storage cells or modular units, one or more vertical members of adjacent prefabricated frames are connected together by one or more fasteners at the interface between adjacent modular storage cells. To 20 enable the connected vertical members to deflect and absorb the thermal expansion of the track support structure, preferably, adjacent vertical members at the interface or junction between adjacent modular storage cells are spaced apart such that adjacent modular sub-frames are spaced apart. As a consequence of the spacing between the vertical members at the junction between adjacent modular storage cells sharing a common prefabricated frame, the distal ends 25 of one or more of the plurality of tracks mounted to the horizontal bracing member of the prefabricated frames are spaced apart. This is because the surface area of the track system extending across the plurality of modular storage cells has been slightly enlarged due to the spacing between the vertical members. As the vertical members are anchored to the floor, bending moments generated as a result of thermal expansion in one or more components of the 30 track system are transferred to the vertical members. As the grid framework structure is formed from a plurality of prefabricated frames arranged in a grid pattern comprising the plurality of modular storage cells, the vertical members of adjacent modular storage cells are allowed to flex or elastically deform within the spacing between the adjacent modular storage cells rather than impacting the vertical members of an adjacent modular storage cell. Bending of the vertical members at the junction between adjacent modular storage cells is absorbed by the 5 movement ofthe modular sub-frames via movement along their respective slip joints. To space adjacent vertical members at the junction between adjacent modular storage cells, optionally, one or more spacers are disposed between the adjacent vertical members at the interface between adjacent modular storage cells sharing the common prefabricated frame. To control the deflection of the vertical members in orthogonal directions, e.g. in the X-10 direction and in the Y-direction, each of tire one or more spacers comprises a first spacing member or portion and a second spacing member or portion, the first spacing member being configured to space adjacent vertical members connected in the first direction by a first spacing and the second spacing member being configured to space adjacent vertical members connected in the second direction by a second spacing. At least three adjacent vertical members 15 are connected together at the interface between adjacent modular storage cells depending on the position of the adjacent vertical members in the supporting framework structure. At the edge of the supporting framework structure, three vertical members from three separate prefabricated frames are connected in the first direction and in the second direction, i.e. two vertical members are connected to the spacer in the first direction and one vertical member is 20 connected to the spacer in the second direction. Similarly, four adjacent vertical members internally of the supporting framework structure from four separate prefabricated frames are connected to the spacer in the first direction and in the second direction. To prevent adjacent vertical members connected in the first direction and / or second direction fouling the storage containers when being lifted through a grid cell, optionally, the first spacing is different to the 25 second spacing. To control the shape of the deflections of the vertical members at the interface between adjacent modular storage cells, the one or more spacers comprises a plurality of spacers distributed along the longitudinal length of the adjacent vertical members at the interface between the adjacent modular storage cells sharing the common prefabricated frame. Optionally, the spacing 30 between the vertical members between adjacent modular storage cells sharing the common prefabricated frame is in the range 5mm to 120mm, preferably between 10mm to 120mm. To control the degree of deflection of the vertical members at the interface between adjacent modular storage cells, optionally, each of the one or more slip joints comprises a limit stop for limiting relative movement between adjacent modular sub-frames a predetermined distance along the substantially horizontal plane. The limit stop prevents excessive movement of the 5 modular sub-frames of the track support structure at the interface between adjacent modular storage cells, which in turn prevents excessive movement or deflection of adjacent vertical members connected in the first direction and in the second direction. To assemble the supporting framework structure from the plurality of prefabricated frames sharing a common prefabricated frame between adjacent modular storage cells, the plurality of 10 prefabricated frames are arranged to form a plurality of modular units, each of the plurality of modular units comprising an interface portion that is arranged to interface with the interface portion of an adjacent modular unit to form a plurality of modular storage cells sharing a common prefabricated frame between adjacent modular storage cells. Preferably, the plurality of prefabricated frames are arranged to form a first type modular unit 15 and a second type modular unit, the second type modular unit having an interface portion that is configured to interface with the first type modular unit in either the first direction or the second direction to form at least a portion of the supporting framework structure comprising at least two modular storage cells sharing at least one common prefabricated frame at the interface between adjacent modular storage cells. To form the at least two modular storage cells sharing 20 a single common prefabricated frame, optionally, the first type modular unit is a closed sided modular unit and the second type modular unit is an open sided modular unit having an open side along one side of the modular unit such that the open side of the second type modular unit is closed by sharing the common prefabricated frame with the first type modular unit. Optionally, the first type modular unit comprises four prefabricated frames arranged to form a 25 closed sided structure and the second type modular unit comprises three prefabricated frames arranged to form a substantially U-shaped structure, the substantially U-shaped structure of the second type modular unit being closed by sharing the common prefabricated frame with any one of the closed sided structure of the first type modular unit. Each of the plurality of the modular units can be standalone structures that are able to independently move relative to each 30 other. Movement of the track system as a result of the movement of one or more of the modular units in either the first direction or the second direction is relieved by the slip joints between adjacent modular units. Optionally, the plurality of prefabricated frames are arranged to form a third type modular unit, said third type modular unit comprising at least two interface portions that are configured to interface with the first, the second and / or third type modular units in the first direction and in the second direction respectively to form at least four modular storage cells. 5 Optionally, the third type modular unit is an open sided modular unit along two sides of the modular unit such that the open sided modular unit along the two sides of the modular unit is closed by sharing two common prefabricated frames with the first and / or second type modular units between adjacent modular storage cells in the first direction and in the second direction. Optionally, the third type modular unit comprises two prefabricated frames arranged to form a 10 substantially L-shaped structure such that the third type modular unit shares two common prefabricated frames between adjacent modular storage cells in the first direction and in the second direction. To interconnect adjacent modular sub-frames of the track support structure between adjacent modular storage cells by the one or more slip joints, the plurality of modular sub-frames of the 15 track support structure comprises a first type modular sub-frame and a second type modular sub-frame, the first type modular sub-frame being a closed sided sub-frame and the second type modular sub-frame being an open sided sub-frame, the first type modular sub-frame being mounted to the first type modular unit and the second type modular sub-frame being mounted to the second type modular unit such that the open side sub-frame of the second type modular 20 sub-frame is closed in the first direction or in the second direction by a side of the first type modular sub-frame at the interface between adjacent modular sub-frames comprising the one or more slip joints. As a result, movement between the first type modular sub-frame and the second type modular sub-frame via the one or more slip joints occurs in either the first direction or the second direction. Optionally, the plurality of modular sub-frames of the track support 25 structure further comprises a third type modular sub-frame, the third type modular sub-frame being an open sided sub-frame along two sides of the sub-frame and being mounted to the third type modular unit such that the open sided sub-frame of the third type modular sub-frame along the two sides of the sub-frame is closed in the first direction and in the second direction by the first type modular sub-frame and / or second type modular sub-frame between adjacent modular 30 storage cells comprising the one or more slip joints. As a result, movement between the third type modular sub-frames and the first type modular sub-frame and / or second type modular sub frame at the interface between adjacent movement modular storage cells occurs in the first direction and in the second direction. Traditionally, the containers or storage bins in a stack are guided through a respective grid cell by vertical uprights at each of the nodes or intersections of the track system. The vertical 5 uprights are typically arranged such that the track system is supported by a vertical upright at each node or junction where the tracks intersect or are interconnected to form multiple storage columns for storing storage containers one or top of the other in vertical stacks. As a result, all four comers of the storage containers cooperate with the vertical uprights as the container is lifted or hoisted towards the load handling device operative on the track system so as to prevent 10 the containers from swinging side to side. The assembly of the prefabricated modular panels to form a three dimensional grid framework structure generates one or more open storage spaces for accommodating multiple stacks of storage containers. The open storage space has a surface area so as to accommodate multiple grid cells of the track system. Tire removal of the vertical uprights has meant that the containers 15 are lifted and raised through a grid cell of the track system in free space by a load handling device operative on the track system. To prevent the grabber device and any storage container attached thereto from swinging when being lifted through a grid cell of the track system, each of the plurality of modular storage cells comprises a plurality of tote guides extending substantially vertically between the track system and the floor, the plurality of tote guides being 20 arranged in a pattern for accommodating a stack of storage containers between the plurality of tote guides and to guide the storage container through a respective grid cell of the track system. Unlike the uprights of the prefabricated modular panels, which are largely load bearing, the plurality of tote guides are intended to guide the grabber device and / or storage container through a grid cell of the track system. Preferably, each tote guide of the plurality of tote guides 25 comprises two perpendicular bin guiding plates extending between the track system and the floor for accommodating a comer of a storage container. The two perpendicular bin guiding plates are configured to accommodate a comer section of a grabber device and / or storage container. Thus, four tote guides would be necessary to accommodate the four comer sections of a standard storage container, which is generally rectilinear in shape. 30 As it is not necessary' for each of the plurality' of tote guides to be load bearing, lower cost manufacturing methods can be used to fabricate the tote guides. Optionally, tine plurality of tote guides are formed from a sheet metal blank folded along parallel fold lines and extend longitudinally along the sheet metal blank to form two substantially perpendicular bin guiding plates defining two tote guides. Examples of folding a sheet metal blank into a tote guide include but is not limited to cold rolling. Whilst it is not necessary to engage or accommodate all four comers of a storage container 5 along the tote guides as the container is hoisted towards the track system by the lifting mechanism of the load handling device, in another embodiment of the present invention, the plurality of tote guides are arranged for guiding one or more containers in a stack along only a pair of diagonally opposed comers of the one or more containers. This gives the grabber device and / or the storage containers a level of lateral stability in the X and Y direction as the storage 10 container is hoisted along diagonally opposed guides. By guiding the grabber device and / or the storage container attached thereto by only diagonally opposed tote guides, tire number of tote guides necessary to guide the grabber device and / or the storage container attached thereto is reduced. In fact, the plurality of tote guides can be arranged at alternate nodes in the first direction (e.g. X direction) and in the second direction (e.g. Y direction), the second direction 15 being substantially perpendicular to the first direction, such that the one or more containers are stacked between two guides at only the diagonally opposed comers of the storage containers. Optionally, the plurality of vertical members of each of the prefabricated frames are braced by one or more bracing members. The one or more bracing members extending between the plurality of vertical members of a prefabricated frame provides a lightweight rigid framed panel 20 comprising a triangulated system of straight interconnected structural bracing elements that are in axial tension or compression. Preferably, the bracing member of each of the plurality-- of prefabricated frames comprises one or more horizontal and / or diagonal bracing members. There are different arrangements of the bracing members to provide different triangulated systems of straight interconnected structural bracing elements that are in axial tension or 25 compression. Optionally, the one or more bracing members are arranged between the plurality of vertical members of the prefabricated braced frame in a cross-brace or a K-brace or a V-brace or an eccentric brace arrangement. Tire term “prefabricated frame” and “prefabricated braced frame” are used interchangeably throughout the description to mean the same feature. Optionally, each of the prefabricated frames comprises an A-frame. Bracing the plurality of 30 vertical members by a straight horizontal bracing member forms at least one drag strut or collector. A drag strut or collector is where tire at least two vertical members are braced by the horizontal bracing member at the top or bottom of the two uprights and functions to collect and transfer diaphragm shear forces to the uprights. To improve the structural integrity of the supporting framework structure, each of the plurality of vertical members in a given prefabricated frame has a cross-sectional profile that is different to the cross-sectional profile of the one or more horizontal and / or diagonal bracing members. For example, the structural integrity of the prefabricated frames can be increased by strengthening the diagonal bracing 5 members in comparison to the other frame members of the prefabricated frame, e.g. by increasing the wall thickness or shape of the cross-sectional profile of the diagonal bracing members. To further increase the structural integrity of the prefabricated frame, each of the one or more horizontal and / or diagonal bracing members can be reinforced by one or more inserts In addition to the track support structure being modular, the plurality of tracks can also 10 comprise a plurality of modular track sections, each modular track section of the plurality of modular track sections comprising substantially perpendicular track section elements so as to provide a track surface extending in the first direction and the second direction, the second direction being substantially perpendicular to the first direction. By having a track system whereby each track section of the plurality of track sections is formed as a unitary or single 15 body, the track section provides a track surface or path extending in transverse directions, e.g. cross shaped. As a result, the number of track sections necessary to build the track system is reduced in comparison to prior art track systems - thereby simplifying the layout of the track sections on the track support structure. For example, a one to one relationship can exist between each of the plurality of track sections and a single node in the track system, in the sense that 20 only a single track section is required at each of the nodes of the track system. A ‘node’ in the track system is the point where the plurality of tracks and / or the track supports intersect in the grid pattern. In prior art track systems, there is a two to one relationship between the number of track sections and a single node in the track system in the sense there is one track section extending in a first direction and a separate track section extending in the second direction. In 25 one example of achieving a one to one relationship between each of the plurality of track sections and each node in the track system, preferably each track section of at least a portion of the plurality of modular track sections comprises: a) a first track section element extending in the first direction; and b) a second track section element intersecting the first track section element and extending in 30 the second direction such that the track section is configured for mounting at one or more nodes of the track support structure. More preferably, each of the plurality of track sections is formed as a unitary body or a single piece body. In other words, each of the plurality of track sections can be cross shaped, having a first track section element extending in the first direction and a second track section element intersecting with the first track section element and extending in the second direction. The first and second track section elements can also be termed transverse portions or branches of the track section. Being formed as a single or unitary body allows the 5 track sections to be mounted to each of the nodes of the track support structure where the track supports intersect. This removes the need to have separate track or rail elements that separately extend in the first and second direction as found in prior art solutions. In addition to simplifying the laying of the plurality of tracks to the track support structure, the cross shaped configuration of the modular track sections enables the modular track sections to bridge the interface between 10 adjacent modular storage cells so as to provide a continuous track surface extending across adjacent modular storage cells. However, the present invention is not limited to having a one to one relationship between a single track section and the number of nodes of the track system. For example, a single track section formed as a unitary body can be configured to extend across multiple nodes of the track 15 system and yet provide a track surface extending in transverse directions. Generally in the art, to ensure that the track system is level and to compensate for an uneven floor, the level of the track system mounted to the vertical uprights is adjusted by having an adjustable levelling foot at the base or lower end of the vertical uprights comprising a threaded shaft that can be extended or retracted relative to the base of the vertical upright. To compensate 20 for the unevenness of the floor or ground, one or more of the prefabricated frames forming the supporting framework structure can be mounted on an adjustable levelling foot comprising a threaded shaft that can be extended or retracted relative to the base of the prefabricated frame. The present invention provides a storage and retrieval system comprising: i) a grid framework structure according to the present invention; 25 ii) a plurality of stacks of containers arranged in storage columns located below the track system, wherein each storage column is located vertically below a grid cell; iii) a plurality of load handling devices for lifting and moving containers stacked in the stacks, the plurality of load handling devices being remotely operated to move laterally on the track system above the storage columns to access the containers through the grid cells, each of said 30 plurality of load handling devices comprising: a) a wheel assembly for guiding the load handling device on the track system; b) a container-receiving space located above the track system; and c) a lifting device arranged to lift a single container from, a stack into the containerreceiving space. The present invention further provides a method of assembling a grid framework structure 5 according to the present invention, comprising the steps of: i) assembling the plurality of prefabricated frames in a grid pattern to form a supporting framework structure comprising a plurality of modular storage cells such that adjacent modular storage cells share a common prefabricated frame; ii) mounting the plurality of modular sub-frames to the supporting framework structure in a 10 substantially vertical direction such that the interfaces between adjacent modular sub-frames are interconnected by the one or more slip joints. The number of slip joints at the interface between adjacent modular storage cells depends on the position of the modular sub-frame in the track support structure which in turn depends on the number of sides of the modular sub-frame that interface w ith an adjacent modular sub-15 frame in the track support structure. For example, a modular sub-frame located in the centre of the track support structure interfaces with four adjacent modular sub-frames, with each of the four sides of the modular sub-frame interfacing with a respective one of the four adjacent modular sub-frames. A modular sub-frame located at an edge of the track support structure interfaces with three adjacent modular sub-frames, so three of the four sides of the modular 20 sub-frame interface with adjacent modular sub-frames, and the fourth side of the modular subframe forms part of the edge of the track support structure. A modular sub-frame located at a comer of the track support structure interfaces with two adjacent modular sub-frames, so two of the four sides of the modular sub-frame interface with adjacent modular sub-frames and the other two sides of the modular sub-frame form part of the edges of the track support structure. 25 Thus, in a given modular sub-frame, one or more slip joints extends in orthogonal directions to cater for movement in the first direction (x-direction) and the second direction (y-direction). To accommodate the one or slip joints at the different sides of the modular sub-frame, each of the plurality of modular sub-frames would need to be mounted to the supporting framework structure in a substantially vertical direction. 30 Optionally, the steps of assembling the supporting framework structure further comprises the steps of: i) assembling four prefabricated frames to form a closed sided modular unit defining a first type modular unit; ii) assembling a plurality of prefabricated frames to the first type modular unit; wherein the plurality of prefabricated frames comprises three prefabricated frames arranged in 5 a substantially U-shaped structure defining a second type modular unit such that the second type modular unit shares the common prefabricated frame with the first type modular unit. In the build of the grid framework structure, the first type modular unit can be defined as the origin of the build and the remaining modular units are built around the origin. The origin provides a stable structure for mounting the prefabricated frames to the origin (first type 10 modular unit). The remaining modular units can be assembled onto the origin by separately assembling the prefabricated frames to the origin or optionally, the second type modular unit can be pre-assembled prior to being assembled onto the first type modular unit. Optionally, the plurality of prefabricated frames further comprises two prefabricated frames arranged in a substantially L-shaped structure defining a third type modular unit such that the 15 third type modular unit shares the common prefabricated frames with the second type modular unit. Optionally, the method further comprising the step of pre-assembling the third type modular unit prior to being assembled onto the second type modular unit. Further features of the present invention will be apparent from die detailed description with 20 reference to the drawings.

Claims

11 12 241. A grid framework structure for supporting one or more robotic load handling devices operative on the grid framework structure, the grid framework structure comprising:i) a supporting framework structure comprising a plurality of prefabricated frames comprising a first set of parallel prefabricated frames extending in a first direction and the second set of parallel prefabricated frames extending in a second direction, the second direction being substantially perpendicular to the first direction such that the plurality of the prefabricated frames are arranged in a three dimensional grid pattern comprising a plurality of modular storage cells for the storage of a plurality of stacks of containers; wherein adjacent modular storage cells share a common prefabricated frame, each of the plurality of prefabricated frames lying in a vertical plane and comprising a plurality of vertical members braced by a bracing member, the supporting framework structure is arranged such that one or more vertical members of adjacent prefabricated frames are connected together by one or more fasteners at tine interface between adjacent modular storage cells;ii) a track system for guiding movement of the one or more robotic load handling devices on the grid framework structure, the track system being mounted to the supporting framework structure and comprising a plurality of tracks arranged in a grid pattern comprising a plurality of grid cells extending across the plurality of modular storage cells such that each of the plurality of modular storage cells supports a sub-group of two or more grid cells of the track system;wherein the track system further comprises a track support structure comprising a plurality of track supports arranged in a grid pattern corresponding to the grid pattern of the track system, the plurality of track supports being interconnected at the intersections of the plurality of track supports in the grid pattern, the track support structure being sub-divided into a plurality of modular sub-frames such that each of the plurality of modular sub-frames comprises the subgroup of two or more grid cells of the track system, the interconnections of the plurality-- of track supports at the interface between the adjacent modular storage cells comprise one or more slip joints such that adjacent modular sub-frames are moveable relative to each other along a substantially horizontal plane via the one or more slip joints;wherein one or more spacers are disposed between the adjacent vertical members at the interface between adjacent modular storage cells; each of the one or more spacers comprises a first spacing member and a second spacing member, the first spacing member being configured11 12 24to space adjacent vertical members connected in the first direction by a first spacing and the second spacing member being configured to space adjacent vertical members connected in the second direction by a second spacing.

2. The grid framework structure of claim 1, wherein the one or more slip joints comprises:-i) a first set of slip joints at the interface between the adjacent modular storage cells in a first direction such that the adjacent modular sub-frames are moveable relative to each other along the substantially horizontal plane in the first direction and;ii) a second set of slip joints at the interface between the adjacent modular storage cells in a second direction such that adjacent modular sub-frames are moveable relative to each other along the substantially horizontal plane in the second direction.

3. The grid framework structure of any one of the preceding claims, wherein the first spacing is different to the second spacing.

4. The grid framework structure of any one of the preceding claims, wherein the one or more spacers comprises a plurality of spacers distributed along the longitudinal length of the adjacent vertical members at the interface between the adjacent modular storage cells.

5. The grid framework structure of any of the preceding claims, wherein the plurality of prefabricated frames are arranged to form a first type modular unit and a second type modular unit, the second type modular unit having an interface portion that is configured to interface with the first type modular unit to form at least a portion of the supporting framework structure comprising at least two modular storage cells sharing at least one common prefabricated frame at the interface between adjacent modular storage cells.

6. The grid framework structure of claim 5, wherein the first type modular unit is a closed sided modular unit and the second type modular unit is an open sided modular unit having an open side along one side of the modular unit such that the open side of the second type modular unit11 12 24is configured to be closed by sharing the common prefabricated frame with the first type modular unit.

7. The grid framework structure of claim 6, wherein the first type modular unit comprises four prefabricated frames arranged to form a closed sided structure and the second type modular unit comprises three prefabricated frames arranged to form a substantially U-shaped structure, and the substantially U-shaped structure of the second type modular unit is closed by sharing the common prefabricated frame with any one of the closed sided structure of the first type modular unit.

8. The grid framework structure of any of the claims 5 to 7, wherein the plurality of modular sub-frames of the track support structure comprises a first type modular sub-frame and a second type modular sub-frame, the first type modular sub-frame being a closed sided sub-frame and the second type modular sub-frame being an open sided sub-frame, the first type modular subframe being configured to be mounted to the first type modular unit and the second type modular sub-frame being configured to be mounted to the second type modular unit such that the open side sub-frame of the second type modular sub-frame is closed by a side of the first type modular sub-frame at the interface between adjacent modular sub-frames comprising the one or more slip joints.

9. The grid framework structure of any of the claims 5 to 8, wherein the plurality of prefabricated frames are arranged to form a third type modular unit, said third type modular unit comprising at least two interface portions that are configured to interface with the first, the second and / or third type modular units to form at least four modular storage cells.

10. The grid framework structure of claim 9, wherein the third type modular unit is an open sided modular unit along two sides of the modular unit such that the open sided modular unit along the two sides of the modular unit is configured to be closed by sharing two common prefabricated frames with the first and / or second type modular units between adjacent modular storage cells.11 12 2411. The grid framework structure of claim 9 or 10, wherein the third type modular unit comprises two prefabricated frames arranged to form a substantially L-shaped structure.

12. The grid framework structure of any of the claims 9 to 11, wherein the plurality of modular sub-frames of the track support structure further comprises a third type modular sub-frame, the third type modular sub-frame being an open sided sub-frame along two sides of the sub-frame and being configured to be mounted to the third type modular unit such that the open sided sub-frame of the third type modular sub-frame along the two sides of the sub-frame is configured to be closed by a respective side of the first type modular sub-frame and / or second type modular sub-frame between adjacent modular storage cells comprising the one or more slip joints.

13. The grid framework structure of any of the claims 9 to 12, wherein the first and / or second and / or third type modular units are standalone sub-structures.

14. The grid framework structure of any of the preceding claims, wherein each of the plurality of modular storage cells comprises a plurality of tote guides extending substantially vertically between the track system and the floor, the plurality of tote guides being arranged in a pattern for accommodating a stack of storage containers between the plurality of tote guides and to guide a storage container through a respective grid cells of the track system.

15. The grid framework structure of claim 14, wherein each tote guide of the plurality of tote guides comprises two perpendicular tote guiding plates extending longitudinally along the length of the tote guide.

16. The grid framework structure of any of the preceding claims, wherein each of the prefabricated frames comprises an A-frame.11 12 2417. The grid framework structure of claim 16, wherein the plurality of vertical members of each of the prefabricated frames are braced by one or more horizontal and / or diagonal bracing members.

18. The grid framework structure of claim 17, wherein the cross-sectional profile of each of the plurality of vertical members in a given prefabricated frame is different to the cross-sectional profile of the one or more horizontal and / or diagonal bracing members.

19. The grid framework structure of claim 17 or 18, wherein each of the one or more horizontal and / or diagonal bracing members is reinforced by one or more inserts.

20. The grid framework structure of any of the preceding claims, wherein the plurality of tracks are configured to be mounted to or integrated to the track support structure.

21. The grid framework structure of claim 20, wherein the plurality of tracks comprises a plurality of modular track sections, each modular track section of the plurality of modular track sections comprising substantially perpendicular track section elements so as to provide a track surface extending in perpendicular directions.

22. The grid framework structure of claim 21, wherein each of the plurality of modular track sections is formed as a single unitary body.

23. The grid framework structure of any of the preceding claims, wherein each of the one or more slip joints comprises a limit stop for limiting relative movement between adjacent modular sub-frames a predetermined distance along the substantially horizontal plane.

24. A storage and retrieval system comprising:i) a grid framework structure as defined in any of the claims 1 to 23;11 12 24ii) a plurality of stacks of containers arranged in storage columns located below the track system 106, wherein each storage column is located vertically below a grid cell;iii) a plurality of load handling devices for lifting and moving containers stacked in the stacks, the plurality-' of load handling devices being remotely operated to move laterally on the track system 106 above the storage columns to access the containers through the grid cells, each of said plurality of load handling devices comprising:a) a wheel assembly for guiding the load handling device on the track system;b) a container-receiving space located above the track system; andc) a lifting device arranged to lift a single container from a stack into the container-receiving space.

25. A method of assembling a grid framework structure as defined in any of the claims 1 to 23, comprising the steps of:i) assembling the plurality of prefabricated frames in a grid pattern to form a supporting framework structure comprising a plurality of modular storage cells such that adjacent modular storage cells share a common prefabricated frame;ii) mounting the plurality of modular sub-frames in a substantially vertical direction to the supporting framework structure such that the interface between adjacent modular sub-frames are interconnected by the one or more slip joints.

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