Grid Framework Structure

Abstract

A grid framework structure (14) for supporting a load handling device (30) operable to move one or more containers, said grid framework structure (14) comprising a plurality of upright members (16) arranged to form a plurality of vertical locations for one or more containers (10) to be guided vertically by the upright members, wherein the plurality of upright members are interconnected by a plurality of grid members (18, 20) arranged in a grid pattern to define nodes at upper ends thereof, the grid members comprising a first set of grid members (18) extending in a first direction and a second set of grid members (20) extending in a second direction, the second set of grid members passing transversely to the first set of grid members in a substantially horizontal plane to form a grid structure (14b) comprising a plurality of grid cells, the grid structure (14b) comprising: 1. A grid framework structure comprising: a track system positioned on a plurality of grid members, the track system comprising a plurality of tracks (22a, 22b) arranged in a grid pattern, the grid structure (14b) comprising a first region (80) and a second region (82), wherein the grid framework structure (14) further comprises a bridging joint assembly (88) arranged as one or more connections between the first region of the grid structure and the second region of the grid structure, said bridging joint assembly (88) comprising at least one mechanical fuse (90) arranged to break under an applied load equal to or greater than a predetermined load, the predetermined load being less than a load for breaking an interconnection between the plurality of upright members and a plurality of grid members of the grid structure to allow the first region of the grid structure to separate from the second region of the grid structure when the applied load exceeds the predetermined load.

Description

[Technical Field]

[0001] The present invention relates to the field of remotely operated load handling devices on tracks positioned on a grid framework structure for handling storage containers or bins stacked within the grid framework structure, and more particularly to a grid framework structure for supporting the remotely operated load handling devices. [Background technology]

[0002] Storage and retrieval systems 1 comprising a three-dimensional storage grid framework structure within which storage containers / bins are stacked on top of each other are well known. PCT Publication WO 2015 / 185628A (Ocado) describes a known storage and fulfilment system in which stacks of bins or containers are arranged within the grid framework structure. The bins or containers are accessed by remotely operable load handling devices on tracks positioned on top of the grid framework structure. This type of system is shown schematically in Figures 1 to 3 of the accompanying drawings.

[0003] As shown in FIGS. 1 and 2, stackable containers known as bins or containers 10 are stacked on top of each other to form stacks 12. The stacks 12 are arranged within a grid framework structure 14 in a warehouse or manufacturing environment. The grid framework is composed of a plurality of storage columns or grid columns. Each grid within the grid framework structure has at least one grid column for storage of a stack of containers. FIG. 1 is a schematic perspective view of the grid framework structure 14, and FIG. 2 is an overhead view showing the stack 12 of bins 10 arranged within the framework structure 14. Each bin 10 typically holds multiple product items (not shown), which may be of the same or different product types, depending on the application.

[0004] The grid framework structure 14 includes a plurality of upright members or columns 16 that support horizontal members 18, 20. Each of the plurality of upright members has a cross-sectional profile including a hollow center section and four corner sections, each of which includes two vertical guide plates extending along the longitudinal length of the upright member that cooperate with the corners of a storage container as the storage container is guided along the upright member. The hollow center sections are preferably box sections.

[0005] The upright members are interconnected at their upper ends by a first set of parallel grid members 18 extending in a first direction and a second set of grid members 20 extending in a second direction. The first set of parallel horizontal grid members 18 are arranged perpendicular to the second set of parallel horizontal grid members 20 to form a grid structure or grid 14b located in a horizontal plane supported by the upright members 16 and comprising a plurality of grid cells 15. For purposes of this description, intersections where grid members meet or intersect within the grid structure constitute nodes of the grid structure. Typically, connecting plates are used to link or join the grid members to the upright members at the intersections. For example, the connecting plate may be cross-shaped with four connecting portions for connecting to the ends of adjacent grid members within the grid structure. However, other means exist for interconnecting multiple grid members to multiple upright members within a grid structure besides using cap plates. WO 2018146304 (Autostore Tech AS) teaches a rail arrangement for wheeled vehicles in a storage system, comprising a first set of parallel rails and a second set of parallel rails. The first and second sets of parallel rails form a grid, where the second set is disposed perpendicular to and intersects the first set, thus forming a grid of parallel rails. The rails comprise a plurality of elongated elements having outer ridges and a central ridge that define a dual track, and the elongated elements further comprise an intermediate ridgeless section, with X- and Y-direction crossing elements arranged to overlap in their respective ridgeless sections, thus defining ridgeless crossways.

[0006] The upright members 16 and grid members 18, 20 are typically fabricated from metal and are typically welded or bolted to one another, or a combination of both. The bins 10 are stacked between the members 16, 18, 20 of the grid framework structure 14 such that the grid framework structure 14 prevents horizontal movement of the stack 12 of bins 10 and guides vertical movement of the bins 10.

[0007] The upper level of the grid framework structure 14 includes a track system comprising rails or tracks 22 arranged in a grid pattern across the top of the stacks 12. The rails or tracks can be integrated into the grid members, or alternatively, the track system can be formed as a separate portion for multiple grid members, in which case the grid members function to support the track system. With additional reference to FIG. 3 , the rails 22 support multiple load handling devices 30 to form the storage and retrieval system 1. A first set 22 a of parallel rails 22 guides movement of the robotic load handling devices 30 in a first direction (e.g., X direction) across the top of the grid framework structure 14, and a second set 22 b of parallel rails 22 positioned perpendicular to the first set 22 a guides movement of the load handling devices 30 in a second direction (e.g., Y direction) perpendicular to the first direction. In this manner, the rails 22 allow for two-dimensional lateral movement of the robotic load handling device 30 in the horizontal XY plane so that the load handling device 30 can be moved into position above any of the stacks 12.

[0008] Rails or tracks typically comprise elongated elements contoured to guide load handling devices over a grid structure, typically contoured to provide a single track surface to allow a single load handling device to travel on the track, or a dual track surface to allow two load handling devices to pass each other on the same track. When the elongated elements are contoured to provide a single track, the track has opposing lips along the length of the track (one lip on one side of the track and another lip on the other side of the track) to guide or limit the lateral movement of each wheel on the track. When the elongated elements are contoured to provide a dual track, the track has two pairs of lips along the length of the track to allow adjacent load handling device wheels to pass each other in both directions on the same track. To provide two pairs of lips, the track typically has a central ridge or lip and lips on either side of the central ridge. In all cases, the wheels of the load handling device are constrained on either side or both sides of the load handling device wheels as they traverse over the grid structure. To prevent wheels of the load handling device from disengaging, the tolerances between adjacent track elements in the grid structure are very small. To accommodate track movement due to temperature differences that cause the track to expand and contract, which can result in buckling or tension in the rails, one or more thermal expansion joints are incorporated into the track system to connect regions of the track system to provide some relief from the result of movement of regions of track.

[0009] WO 20200774257 (Autostore Technology AS) relates to an expansion joint for connecting areas of a rail-based grid storage system, the expansion joint comprising a first rail element and a second rail element, the rail elements being elongated and configured to slide longitudinally relative to one another within a junction area where they overlap, the expansion joint having a contoured upper surface defining one or more tracks for supporting container handling vehicles, the tracks extending from the first rail element through the junction area to the second rail element, within the junction area each rail element presents a portion of the or each track of the contoured upper surface, whereby there is a transition extending along the expansion joint from the first rail element to the second rail element of the or each track.

[0010] A known load handling device 30, shown in Figures 4 and 5, includes a vehicle body 32, as described in PCT Patent Publication WO 2015 / 019055 (Ocado), incorporated herein by reference, where each load handling device 30 covers only one grid space of a grid framework structure 14. Here, the load handling device 30 includes a wheel assembly including a first set of wheels 34, consisting of a pair of wheels at the front of the vehicle body 32 and a pair of wheels 34 at the rear of the vehicle body 32, for engaging a first set of rails or tracks to guide movement of the device in a first direction, and a second set of wheels 36, consisting of a pair of wheels 36 on each side of the vehicle 32, for engaging a second set of rails or tracks to guide movement of the device in a second direction. Each of the wheel sets is driven to enable movement of the vehicle in the X and Y directions, respectively, along the rails. One or both sets of wheels are vertically movable to lift each set of wheels off their respective rails, thereby enabling the vehicle to move in a desired direction.

[0011] The load handling device 30 is equipped with a lifting device or crane mechanism for lifting storage containers from above. The crane mechanism includes a winch tether or cable 38 wound on a spool or reel (not shown) and a gripper device 39. The lifting device includes a set of vertically extending lifting tethers 38 connected near or at four corners of the lifting frame 39, otherwise known as gripper devices (one tether near each of the four corners of the gripper device), for releasable connection with the storage container 10. The gripper device 39 is configured to releasably grip the top of the storage container 10 for lifting the storage container from a stack of containers in a storage system of the type shown in FIGS. 1 and 2.

[0012] The wheels 34, 36 are arranged around the periphery of a cavity or recess within the lower portion, known as a container receiving space 40. The recess is sized to accommodate the container 10 when it is lifted by a crane mechanism, as shown in FIGS. 5(a) and 5(b). When in the recess, the container is lifted off the underlying rails to allow the vehicle to move laterally to different locations. Upon reaching a destination location, such as another stack, an access point within a storage system, or a conveyor belt, the bin or container can be lowered from the container receiving portion and released from the gripper device. The container receiving space is not limited to the container receiving space 40 located within the vehicle body 32. The container receiving space can be installed below a cantilever, in which case the vehicle body of the load handling device has a cantilever structure as described in WO 2019 / 238702 (Autostore Technology AS). For the purposes of the present invention, the term "vehicle body" is interpreted as optionally covering the cantilever such that a gripper device is positioned below the cantilever.

[0013] To access the contents of storage containers, the majority of grid columns are storage columns, i.e., grid columns in which storage containers are stored in stacks. However, grid structures typically have at least one grid column that is not used to store storage containers, but which includes locations or grid cells 15 where load handling devices can drop off and / or pick up storage containers so that the storage containers can be transported to a second location (not shown in prior art figures) where they can be accessed from outside the grid or transferred into or out of the grid. In the art, such locations or grid cells are typically referred to as "ports," and the grid column in which the port is located may be referred to as a "delivery column." A storage grid includes two delivery columns. The first delivery column may, for example, include a dedicated drop-off port where container handling vehicles can drop off storage containers to be further transported through the delivery column to an access or transfer station, and the second delivery column may include a dedicated pickup port where container handling devices can pick up storage containers transported through the delivery column from the access or transfer station. The storage containers are delivered into the access station and exit the access station via the first and second shipping columns, respectively.

[0014] Upon receiving a customer order, a load handling device operable to move on a track is instructed to pick up a storage bin containing the order's items from a stack within the grid framework structure and transport the storage bin via a delivery column to a pick station, where the items can then be removed from the storage bin. Typically, the load handling device transports the storage bin or container to a bin lifting device integrated within the grid framework structure. A mechanism of the bin lifting device lowers the storage bin or container to the pick station. At the pick station, the items are removed from the storage bin. Picking can be performed manually or by a robot as taught in GB Patent No. 2524383 (Ocado Innovation Limited). After removal from the storage bin, the storage bin is transported to a second bin lifting device, which then lifts the storage bin to grid level to a pickup port for removal by the load handling device and transports it back to its location within the grid framework structure.

[0015] A separate area is provided adjacent to the storage column to accommodate an access station for a load handling device to drop off or pick up storage containers from the pick station. Typically, the separate area is provided by incorporating a mezzanine supported by vertical beams within an adjacent grid framework structure. The mezzanine provides a separate area for accommodating one or more pick stations. Typically, the separate area is a tunnel flanked on both sides by grid framework structures. Grid structures from adjacent grid framework structures extend across the top of the mezzanine to connect to the grid structure on both sides of the mezzanine such that the grid structure is positioned in a substantially horizontal plane. One or more delivery and / or pickup ports are assigned to one or more grid cells of the grid structure extending across the mezzanine so that load handling devices operable on the grid structure can drop off and pick up storage containers from the pick stations below. As a result of the grid structure extending across the mezzanine, the grid structure above the mezzanine tends to be shallower than the grid framework structures on either side of the mezzanine, i.e., it can accommodate only one or two layers of containers in a stack. The mezzanine is supported by separate vertical beams. The vertical beams supporting the mezzanine abut the grid framework structure on either side of the mezzanine. In addition to one or more pick stations, the separate area created by the mezzanine can accommodate various other stations, including, but not limited to, a charging station for charging rechargeable batteries that power the load handling devices on the grid, a service station for performing routine maintenance on the load handling devices, etc. Because such stations require manual labor, one or more workers tend to be located below the mezzanine. These workers include, but are not limited to, pickers at the pick station, service workers at the work station, etc.

[0016] Grid framework structures are subject to a variety of external and internal forces. These include, but are not limited to, ground movement, which may be due to the composition of the ground or soil type; forces generated by the movement of load handling devices on the grid framework structure, which may weigh more than 100 kg; forces generated by movement resulting from nearby structures or moving vehicles, such as trains; or forces generated during earthquakes or storms. To ensure the stability of the grid framework structure, prior art storage and retrieval systems rely heavily on various supports and braces located within or at least partially along the perimeter of the grid. However, using various supports and braces (anti-shift braces) to stabilize the grid framework structure from internal and external forces is disadvantageous for several reasons. The grid framework structure occupies space or area that could be utilized by the grid to store containers, preventing optimal use of the space or area available for container storage. The need for support structures can limit available options for positioning the grid framework structure, as any auxiliary grid support structures often require connections to surrounding structures, such as the interior walls of a building, necessitating cost-ineffective support structure requirements.

[0017] WO 2019 / 101367 (Autostore Technology AS) teaches a grid support structure for integration into a storage grid structure of a collocated automated storage system. The grid support structure is comprised of four storage columns interconnected by a plurality of vertically inclined support struts. The storage column profile has a cross section with a hollow center section and four corner sections, each with two vertical bin guide plates for accommodating the corners of a storage bin. The support struts have a width that allows them to fit between two parallel guide plates so as not to impair the storage column's ability to accommodate a stack of containers or storage bins.

[0018] While some movement in the grid framework structure as a result of thermal expansion and contraction is considered acceptable to provide relief for the track system, excessive movement of the grid framework structure is not considered acceptable because it could compromise the structural fasteners that hold the grid framework structure together.

[0019] Much of the world's population lives along earthquake fault lines or in the path of powerful storms such as hurricanes and tornadoes. Locating grid-frame structures in such areas poses a risk of structural damage from earthquakes and storm events because current grid-framework structures may not hold the grid structure together. Powerful earthquakes and storm events can result in the structural integrity of the grid-framework structure failing, for example, as a result of structural fasteners failing to keep the grid securely attached to the uprights. Earthquakes can be labeled into four categories, labeled Type A, B, C, or D, depending on their severity, with Type A being considered the least powerful and Type D the most powerful. Types A-D can be graded by their spectral acceleration, which is the maximum acceleration, measured in g, experienced by objects above the Earth's surface during an earthquake. Type D is considered to represent the most powerful seismic events, typically having measured spectral accelerations in the range of 0.5g to 1.83g (short-term spectral response accelerations SDS, see https: / / www.fegstructural.com / seismic-design-category-101 / ), and is responsible for most building failures. When a powerful seismic event acts on a structure, the three-dimensional dynamic forces can compromise the structural fasteners that hold the grid framework structure together, causing them to loosen or break away from the members in which they are embedded, or, if the structural fasteners remain in place, they may penetrate through the structural components.

[0020] During ground movement resulting from a seismic event, grid framework structures tend to vibrate. The vibration of grid framework structures can be described by transverse and longitudinal waves. Longitudinal waves are waves in which the displacement of the grid framework structure is in the same direction as the ground movement, while transverse wave vibrations are perpendicular to the ground movement. In either case, the amplitude of the vibration of the grid framework structure is highly dependent on the extent of the ground movement, which in turn depends on the earthquake category. In Category D earthquakes, the amplitude of the vibration is significantly greater than in Category A earthquakes. Because the upright members of the grid framework structure are interconnected at their upper ends by multiple grid members extending in first and second directions, the movement of the grid framework structure can be concentrated at the joints where the grid members meet or intersect at the vertical upright members, resulting in bending moments. While thermal expansion joints provide some cushioning for movement of the track system to avoid derailment of the load handling device, this is not the case when the movement of the track system is excessive enough to loosen or, in the worst-case scenario, separate the structural fasteners at the interconnections, i.e., during a seismic event. Not only are the structural fasteners interconnecting the grid members together subjected to bending moments as a result of ground movement, but other structural fasteners connecting the grid members together and / or the bracing members supporting the upright members are also subjected to excessive forces. The forces experienced at the interconnections are exacerbated the taller the grid framework structure is as a result of the amplitude of vibration of the grid framework structure.

[0021] Individual containers may be stacked in vertical layers, and their location within the grid framework structure or "beehive" may be displayed using a three-dimensional coordinate system to represent the location of the load handling device or container and the depth of the container (e.g., (X, Y, Z), container at depth W). Similarly, locations within the grid framework structure may be displayed in two dimensions to represent the location of the load handling device or container and the depth of the container (e.g., (X, Y), container at depth W). For example, Z=1 identifies the top layer of the grid, i.e., the layer immediately below the rail system, Z=2 is the second layer below the rail system, and so on down to the bottom layer at the bottom of the grid. Depth Z can be as high as 21 levels, and considering that typical storage containers can be 30-40 cm high, the amplitude of vibration of the grid framework structure can be extremely severe during a seismic event.

[0022] Considering a rough example where the vibration of a grid framework structure fixed to the ground is equivalent to the vibration of a pendulum, the displacement, s, of the grid framework structure from the vertical during ground movement can be given by the following equation:

[0023]

number

[0024] where L is the effective height of the grid framework structure and θ is the angle the grid framework structure makes with the vertical. When θ is expressed in radians, s is considered to be the amplitude of vibration of the grid framework structure. Therefore, according to Equation (1), the higher the height of the grid framework structure, the greater the amplitude of vibration of the grid framework structure during ground movement. As a result of excessive vibration of the grid framework structure due to a seismic event, the structural fasteners holding the grid members and / or upright members together may weaken and, in a worst-case scenario, may cause the grid framework structure to collapse. Given that people work below the grid structure, especially below the mezzanine level as discussed above, the collapse of the grid framework structure would endanger the lives of those below the mezzanine level. In addition to disrupting the area of ​​the grid framework structure, the vibration of the grid framework structure also makes storage containers and / or their contents stacked between the upright members more susceptible to being thrown out. There is a need for grid framework structures, particularly those that separate areas where people are located, to reduce the risk of injury to people if the grid framework were to break apart or, in a worst-case scenario, collapse. Summary of the Invention

[0025] Applicant has alleviated the above problem by separating at least a portion of the grid structure with a bridging joint assembly including at least one mechanical fuse arranged to break under an applied load less than the load required to break the grid member interconnections within the grid structure. Preferably, the at least one mechanical fuse is arranged to break under an applied load equal to or greater than a predetermined load to separate at least a portion of the grid structure from the remainder of the grid structure. The predetermined load is a load less than the load required to break the grid member interconnections within the grid structure. For example, a connection between an upright member and a grid member can be an example of a grid member interconnection within the grid structure. Having one or more of the grid member connections within the grid structure with a mechanical fuse that breaks under an applied load less than the load that would break the grid member interconnections within the grid structure allows selected portions of the grid structure to break under the applied load. Therefore, for clarity, the applied load is a load that breaks the mechanical fuse but does not break the grid member interconnections within the grid structure. This is particularly advantageous when at least a portion of the grid structure is above a mezzanine level below which people work. Separating at least a portion of the grid structure helps prevent the remainder of the grid structure from causing a fatal impact on that at least a portion of the grid structure. In other words, separating at least a portion of the grid structure from the remainder of the grid structure prevents bending moments generated within the remainder of the grid structure from toppling that at least a portion of the grid structure, thereby helping to mitigate injuries to people working below at least a portion of the grid structure, e.g., a mezzanine level.

[0026] More particularly, the present invention provides a grid framework structure for supporting a load handling device operable to move one or more containers, said grid framework comprising: a plurality of upright members arranged to form a plurality of vertical locations for one or more containers to be guided vertically by the upright members; wherein the plurality of upright members are interconnected at their upper ends by a plurality of grid members arranged in a grid pattern comprising a first set of grid members extending in a first direction and a second set of grid members extending in a second direction, the second set of grid members passing transversely to the first set of grid members in a substantially horizontal plane to form a grid structure comprising a plurality of grid cells; the grid structure comprises a track system positioned on a plurality of grid members, the track system comprising a plurality of tracks arranged in a grid pattern; the grid structure comprises a first region and a second region; and a grid framework structure, wherein the grid framework structure further comprises a bridging joint assembly disposed as one or more connections between a first region of the grid structure and a second region of the grid structure, the bridging joint assembly comprising at least one mechanical fuse disposed to break under an applied load equal to or greater than a predetermined load, the predetermined load being less than a load for breaking the interconnections between the plurality of upright members and the plurality of track members of the grid structure to allow the first region of the grid structure to separate from the second region of the grid structure when the applied load exceeds the predetermined load.

[0027] At least a portion of the grid structure can represent a first region of the grid structure, and a remaining portion of the grid structure can represent a second region of the grid structure. The first region of the grid structure can be disposed on a mezzanine level such that the grid structure extends across the mezzanine level. Optionally, the first region of the grid structure includes one or more ports through which storage containers can be transferred from and / or into the grid framework structure via grid cells of the grid structure. For example, a delivery port can be disposed in the first region of the grid structure on the mezzanine level, such that a robotic load handling device operable on the grid structure can travel from the second region into the first region of the grid structure and deliver a storage container via the delivery port to a pick station below the mezzanine level that supports the first region of the grid structure. The reverse is true when one or more storage containers are retrieved from a pick station below the mezzanine level via a pickup port.

[0028] Optionally, the at least one mechanical fuse comprises at least one shear pin configured to break when an applied load in a direction parallel to the first and / or second directions exceeds or equals a predetermined load. For example, the mechanical fuse can comprise a bolt having at least one failure zone configured to break under a shear load. The failure zone can be a reduced cross-sectional area of ​​the bolt that breaks under the predetermined load. Other names for the shear pin include, but are not limited to, a breakaway bolt or a fuse bolt. Typically, during ground movement as a result of a seismic event, movement of the grid framework is along a direction along the first and / or second directions. Bending moments generated in the grid structure as a result of the ground movement are transferred along grid members extending along the first and second directions. When the bending moment exceeds or equals a predetermined threshold to break the mechanical fuse, a first region of the grid structure becomes separated from a second region of the grid structure. As discussed above, the wheel assemblies of the robotic load handling device include pairs of wheels at the front and rear of the vehicle body and a pair of wheels on each side of the wheel body. To enable the robotic load handling device to move on the grid structure, preferably bridging joint assemblies are positioned as two or more connections between a first region of the grid structure and a second region of the grid structure.

[0029] Optionally, the bridging joint assembly is configured to connect the ends of adjacent grid members in a grid structure. One example of incorporating a mechanical fuse into the bridging joint assembly when connecting the ends of adjacent grid members together is by connecting at least one bracket to the ends of the adjacent grid members with a plurality of fasteners, at least one of the plurality of fasteners including at least one mechanical fuse arranged such that the bracket separates from at least one end of the adjacent grid member when an applied load on the at least one mechanical fuse exceeds or equals a predetermined load. For example, the bracket can be a plate fastened to the ends of the adjacent grid members with a plurality of fasteners that overlap and extend across the ends of the adjacent grid members, one or more of the plurality of fasteners being a mechanical fuse. When an applied load on the mechanical fuse exceeds or equals a predetermined load, the mechanical fuse breaks, causing the bracket to separate from at least one end of the grid member. However, other means exist for incorporating a mechanical fuse into the bridging joint assembly of the present invention. For example, instead of fabricating one or more fasteners as a mechanical fuse, at least one grid member itself can be fabricated as a mechanical fuse extending between the ends of adjacent grid members, the mechanical fuse being configured to break when an applied load exceeds or equals a predetermined load.

[0030] Ground movement as a result of a seismic event generates lateral forces that move the grid framework structure, but there are also other forces that move the grid framework structure and, without some form of relaxation, cause it to distort or buckle. For example, temperature differences in ambient temperature or within the building or area in which the grid framework structure is located can also cause the grid structure and ultimately the track system to distort as a result of thermal expansion and contraction of the grid structure and / or the track system. Track expansion and contraction due to temperature differences can result in buckling or excessive tension in the track, potentially causing movement of one of the grid structure components and, in a worst-case scenario, causing a robotic load handling device to derail from the track system. Expansion and contraction of the grid structure and / or track system can be a common occurrence due to temperature fluctuations, and some type of relaxation is needed in the grid structure to mitigate movement of the grid structure as a result of thermal expansion and contraction of the grid members so as not to derail one or more robotic load handling devices operable on the track system.

[0031] To accommodate movement of the grid structure as a result of thermal expansion and contraction, the bridging joint assembly preferably includes at least one sliding bearing arranged to cooperate with a slot in the bracket and / or at least one end of the adjacent grid member within a joint area where the at least one bracket overlaps the at least one end of the adjacent grid member to allow the at least one bracket and / or at least one end of the adjacent grid member to slide relative to one another. Compared to movement as a result of thermal expansion and contraction, movement as a result of a seismic event may be much more extensive. The sliding bearing provides cushioning to the grid structure to accommodate movement as a result of thermal expansion and contraction, but should movement of the grid structure be excessive enough to otherwise cause collapse of the grid framework structure, a mechanical fuse fastening the ends of the adjacent grid members together can be broken to separate a first region of the grid structure.

[0032] As an alternative to, or in addition to, brackets connecting the ends of adjacent grid members, a bridging joint assembly may be positioned to connect at least one of a plurality of upright members to at least one of a plurality of grid members where the grid members intersect within the grid structure, i.e., at a node of the grid structure. For example, the bridging joint assembly may include a cap plate, the cap plate being cross-shaped with four connection portions for connecting to separate grid members within the grid structure, at least one of the four connection portions being connected to the grid member by at least one mechanical fuse. When an applied load exceeds or equals a predetermined load, the mechanical fuse causes the grid member connected to the cap plate to separate from the cap plate, resulting in a break in one of the connections at the node of the grid structure where the grid members intersect.

[0033] To prevent the wheels of the robotic load handling device from disengaging due to movement of the track as a result of thermal expansion and contraction, the bridging joint assembly preferably further includes a thermal expansion joint comprising a first track element and a second track element, wherein the bridging member extends across the ends of the first and second track elements to provide a continuous track surface extending longitudinally in either the first or second direction across the ends of the first and second track elements. The bridging member of the thermal expansion joint is positioned across the first and second track elements to transfer the weight of the wheels of the robotic load handling device from the first track element to the second track element without or with only minimal stepping in the track as they pass across the thermal expansion joint. Preferably, the bridging member has a first end attached to the first track element and a second end movable relative to the second track element.

[0034] The first and second track elements are elongated and configured to move longitudinally relative to one another within a joint region where the bridging member extends across the first and second track elements.

[0035] Optionally, the second end of the bridging member is configured to be received within a correspondingly shaped recess in the second track element to provide a continuous track surface. For example, the bridging member comprises a portion of the upper contour of the track surface, and the correspondingly shaped receiving recess comprises the remaining portion of the upper contour of the track surface, such that when the second end of the bridging member is received within the correspondingly shaped receiving recess of the second track element, the upper contour of the track surface is completed to allow movement of the robotic load handling device across the thermal expansion joint. The upper contour of the track surface can be a single track or a dual track as discussed above.

[0036] Optionally, the second end of the bridging member is positioned to overlap the second track element. Optionally, the bridging member further comprises a guide member positioned to pivot along a groove in the second track element, thereby restricting the bridging member from moving along the groove. The guide member can function as a sliding bearing positioned to slide along the runner to provide a continuous track surface as the first and second track elements move relative to each other. Other means known in the art for moving the first track element relative to the second track element to provide a continuous track surface extending from the first track element to the second track element are applicable to the present invention.

[0037] Thermal expansion joints ensure that the track surface is maintained during expansion and / or contraction of the grid members. Thermal expansion joints can also accommodate small distortions of the grid structure as a result of ground movement. However, when ground movement becomes excessive in a manner characteristic of a seismic event, the mechanical fuses connecting adjacent grid member ends or uprights break, thereby separating different regions of the grid structure.

[0038] When the bridging member extends across the ends of the first and second track elements, the bridging joint assembly further includes a support disposed between the ends of the first and second track elements, the support being positioned to support the bridging member within the interface area between the ends of the first and second track elements. Without the support, there is a risk that at least a portion of the bridging member will deflect under the weight of a robotic load handling device traveling across the bridging joint assembly within the interface area where the ends of the first and second track elements separate. In other words, the separation of the ends of the first and second track elements creates a gap that is spanned by the bridging member extending across the gap to provide a continuous track surface.

[0039] Preferably, at least a portion of the plurality of upright members are arranged to form a plurality of vertical storage columns for stacking one or more storage containers between at least a portion of the plurality of upright members. The grid framework structure may be divided into a first region for moving storage containers into and out of the grid framework structure and a second region for storing one or more storage containers in the plurality of vertical storage columns, where the storage containers are stacked between and guided by the upright members. The first region of the grid framework structure is, in its majority, provided with one or more ports through which storage containers can be transferred from and / or into the framework structure. Preferably, the second region of the grid structure is arranged above at least a portion of the plurality of upright members forming the plurality of vertical storage columns.

[0040] Preferably, the plurality of upright members comprises first and second sets of upright members, at least a portion of the plurality of upright members defining the second set of upright members such that the first region of the grid structure is disposed above the first set of upright members. Optionally, the length of the first set of upright members is different from the length of the second set of upright members. When the second set of upright members is positioned to store one or more stacks of storage containers within the vertical storage column, the first set of upright members may be significantly shorter than the second set of upright members because the first set of upright members is primarily used to guide the storage containers into and / or out of the grid framework structure.

[0041] The second set of uprights is arranged to form a plurality of vertical storage columns, and is therefore significantly longer than the first set of uprights, which are primarily used to guide storage containers into and / or out of the grid framework structure. Thus, the vertical storage columns provided by the second set of uprights can be used to store stacks of storage containers that may be as tall as 21 storage containers. The first set of uprights is typically positioned above the mezzanine level. When fulfilling customer orders, one or more of the storage containers containing items for fulfilling the customer order are removed from their vertical storage columns and transported by a robotic load handling device to a first region of the grid structure, where the storage containers are lowered via a delivery port into a pick station below the mezzanine level. The same principle applies when a load handling device operable on the first region of the grid structure removes a storage container from the pick station via a pickup port, where the storage container is then transported to its appropriate vertical storage column below the second region of the grid structure.

[0042] Ground movement resulting from a seismic event inevitably causes the portion of the grid framework structure comprising the second set of longer upright members to vibrate at a greater amplitude than the first set of shorter upright members. The greater amplitude of vibration of the second set of longer upright members imposes strain on the grid members linking or connecting the first regions of the grid structure supported by the first set of shorter upright members. In a worst-case scenario, this strain loosens and eventually causes the interconnections of the grid members at the uprights to fail. This strain is exacerbated by the movement of storage containers stacked between the uprights.

[0043] A bridging joint assembly of the present invention configured to connect a first region of a grid structure to a second region of the grid structure to prevent a longer portion of the grid framework structure comprising a second set of upright members from straining the interconnections of the grid members in the first region of the grid structure comprises at least one mechanical fuse arranged to break under an applied load equal to or greater than a predetermined load, the predetermined load being set to be less than the load for breaking the interconnections between the plurality of upright members and the plurality of grid members of the grid structure so as to allow the first region of the grid structure to separate from the second region of the grid structure when the applied load exceeds or equals the predetermined load.

[0044] Optionally, the plurality of grid members comprises a plurality of first-type grid members arranged in a grid pattern to define a first region of the grid structure and a plurality of second-type grid members arranged in a grid pattern to define a second region of the grid structure, the plurality of first-type grid members being different from the plurality of second-type grid members. To strengthen the portion of the grid framework structure used for storing the storage containers, each grid member of the plurality of second-type grid members has a greater bending strength than each grid member of the plurality of first-type grid members. This is because during a seismic event, bending moments resulting from vibration of the upright members are largely transferred at the interconnections where the plurality of grid members intersect. To resist bending moments at the intersections of the grid members, the grid members are constructed with a greater cross-sectional wall thickness than conventional grid members. Conventional grid members are typically constructed from relatively thin metal strips comprising back-to-back C-sections that are bolted together. However, such grid members cannot withstand excessive ground movement resulting from a Type D earthquake event, in which the bending moment in the grid members can eventually loosen and sever the fasteners interconnecting the grid members to the upper ends of the upright members. To mitigate this effect, the grid members are constructed to resist excessive bending moments. For example, the grid structure of the seismic grid framework structure may comprise tubular beams. In contrast to back-to-back C-sections bolted together, the tubular beams provide improved stiffness and strength. The tubular cross-sectional profile of the grid members provides resistance to bending moments in multiple directions. Instead of using one or more bolts to interconnect the grid members where they meet at the upper ends of the upright members, the tubular beams are welded together at the joints where the grid members meet at the intersections to form rigid joints with little or no play. The welds at the joints provide superior stiffness compared to bolts, which are more prone to loosening. The second region of the grid structure can optionally form part of the seismic grid framework structure.

[0045] Due to the difference in height between the upright members supporting the first region of the grid structure extending above the mezzanine level and the upright members supporting the second region of the grid structure, the bending moment of the grid members in the first region is significantly smaller than that in the second region of the grid structure. As a result, the grid members in the first region of the grid structure can optionally be constructed from weaker grid members, such as back-to-back C-sections, to keep costs down because they are not subject to the same bending moment as the grid members in the second region of the grid structure during a seismic event. Typically, the mezzanine level supporting the first region of the grid structure is constructed from structurally rigid upright support posts extending upward from the ground to ensure that the grid members extending above the mezzanine level are at the same level as the second region of the grid structure extending above the vertical storage columns. The height of the upright support posts defines the height of the mezzanine level, which in turn defines the level of the grid structure supported by the mezzanine level, ensuring that the grid structure lies in a substantially horizontal plane. Typically, the upright support posts are I-beams that resist bending moments relative to the upright members forming the vertical storage columns. The rigidity of the upright support posts allows a smaller bending moment to be experienced by the grid members, thus providing an advantage for constructing the first region of the grid structure from grid members that are weaker than the second region of the grid structure. Even though the grid members in the second region of the grid structure are able to resist bending moments resulting from lateral forces from a seismic event, when connected to the first region of the grid structure, lateral forces from the second region of the grid structure are transferred to the grid members in the first region of the grid structure. This can have the undesirable effect of weakening the fasteners interconnecting the grid members to the tops of the upright members in the first region of the grid structure. A bridging joint assembly comprising at least one mechanical fuse helps mitigate failure of grid members in the first region of the grid structure due to lateral forces experienced by the second region of the grid structure.When the lateral force exceeds or equals a predetermined load, the mechanical fuse shears and separates the first region of the grid structure from the second region of the grid structure, thereby ensuring that the grid members within the first region remain intact. However, the invention is not limited to the grid members forming the first region of the grid structure being different from the grid members forming the second region of the grid structure; the same type of grid members can extend throughout the entire grid structure.

[0046] The present invention provides a storage and retrieval system, comprising: i) a grid framework structure according to any one of claims 1 to 22; ii) a plurality of stacks of containers disposed in storage columns positioned below a grid, wherein each storage column is positioned vertically below a grid cell; iii) a plurality of load handling devices for lifting and moving the stacked containers in the stack, the plurality of load handling devices being remotely operated to move laterally on a grid above the storage columns to access the containers through the grid cells, each of the plurality of load handling devices comprising: a) a wheel assembly for guiding a load handling device on a grid; b) a container receiving space located above the grid; c) a lifting device arranged to lift a single container from the stack into the container receiving space; A storage and retrieval system is provided, comprising:

[0047] Further features of the present invention will become apparent from the detailed description. [Brief explanation of the drawings]

[0048] DETAILED DESCRIPTION OF THE INVENTION

[0049] Grid Framework Structure The present invention addresses known features of storage systems, such as the grid framework structure and load handling devices described above with reference to Figures 1 to 5. Figure 6 shows a top view of a section or portion of a conventional grid structure 50 comprising four adjacent grid cells 42, and Figure 7 shows a side perspective view of a single grid cell 42 supported by four vertical uprights 16 to form a single vertical storage column 44 for storage of one or more containers 10 in a stack. Figures 8(a and b) show perspective views of the uprights arranged to form a vertical storage column 44 for storing containers 10 within the vertical storage column 44. Figure 8b shows a diagram of the vertical stacking of containers 10 between the uprights 16.

[0050] Each of the vertical uprights 16 is generally tubular. In a transverse cross-section of the storage column 44 in a horizontal plane shown in FIG. 2 , each vertical upright 16 includes a hollow center section 46 (typically a box section), with one or more guides 48 attached to or formed at the corners of the hollow center section 46 extending along the longitudinal length of the vertical upright 16 to guide the movement of containers along the vertical storage column 44. The one or more guides 48 include two vertical container guide planes. The two vertical container guide planes are positioned to accommodate the corners of a container or stack of containers. In other words, each corner of the hollow center section 46 defines two sides of a substantially triangular area that can accommodate the corners of a container or storage bin. The corners are equally spaced around the hollow center section 46 so that multiple vertical uprights 16 can provide multiple adjacent storage columns, and each vertical upright 16 may be common to or shared with up to four separate storage columns. Also shown in FIG. 7 is that each of the vertical uprights 16 is mounted at the foot of the vertical upright on an adjustable grid level adjustment mechanism 19 which comprises a base and a threaded shaft that can be extended or retracted to compensate for uneven floors.

[0051] The transverse cross-section of a storage column 44 in a horizontal plane in FIG. 2 shows that each storage column 44 is composed of four vertical uprights 16 positioned at the corners of a container or storage bin 10. A storage column 44 corresponds to a single grid cell. The cross-section of the vertical uprights 16 is constant along the entire length of the vertical uprights. The perimeter of multiple containers or storage bins in a horizontal plane in FIG. 2 shows the container or storage bin having four corners and the arrangement of the four vertical uprights 16 at the corners of the container or storage bin within the vertical storage column 44. The corner section of each of the four vertical uprights, i.e., one from each of the four vertical uprights, ensures that a container or storage bin stored within the storage column 44 is guided into the correct position relative to any containers or storage bins stored within the storage column or stacks of containers or storage bins in surrounding storage columns. A robotic load handling device (not shown) operable on the grid structure 50 can lift the container or storage bin as it is guided along the vertical uprights 16 through the grid cells 42. Thus, the vertical uprights 16 have a dual purpose: (a) to provide structural support for the grid structure 50, and (b) to guide the containers or storage bins 10 through their respective grid cells 42 into position.

[0052] The top plan view of a section of a grid structure 50 shown in FIG. 6 shows a series of horizontal intersecting beams or grid members 18, 20 arranged to form a plurality of rectangular frames that make up grid cells 42; more specifically, a first set of grid members 18 extend in a first direction X, and a second set of grid members 20 extend in a second direction Y, with the second set of grid members 20 running transversely relative to the first set of grid members 18 in a substantially horizontal plane; i.e., the grid structure is represented by Cartesian coordinates in the X and Y directions. The terms “vertical uprights,” “upright members,” and “upright columns” are used interchangeably in this description to mean the same thing or feature. For purposes of this description, the points or junctions where grid members intersect or meet, indicated by squares in FIG. 6 , may be defined as nodes or intersections 52. It is clearly apparent from the layout of at least a portion or section of the known grid structure 50 making up four adjacent grid cells 42 shown in Figure 6 that each intersection or node 52 of the grid structure 50 is supported by a vertical upright 16, i.e., both of which are co-located. From the section or at least a portion of the grid structure 50 shown in Figure 6, four adjacent grid cells are supported by nine vertical uprights 16, i.e., three sets of vertical uprights 16 support three columns of the grid structure, where each column comprises three nodes 52.

[0053] Each grid member of the present invention may comprise a track support 18, 20 and / or a track or rail 22a, 22b (see FIG. 9 ), whereby the track or rail 22a, 22b is mounted to the track support 18, 20. A load handling device is operable to move along the track or rail 22a, 22b of the present invention. Alternatively, the track 22a, 22b may be integrated into the track support 18, 20 as a single body, for example, by extrusion. In certain embodiments of the present invention, the grid members comprise the track support 18, 20, and the track or rail 22a, 22b is mounted to the track support 18, 20. At least one grid member in the set, e.g., a single grid member, may be subdivided or sectioned into separate grid elements that may be joined or linked together to form grid members 18, 20 extending in a first direction or a second direction (see FIGS. 9 and 14 ). Where the grid members comprise track supports, the track supports may also be subdivided into separate track support elements that are linked together to form the track supports (see FIGS. 10 and 13). Separate track support elements making up the first and second axially extending track supports are shown in FIG. 9. Individual track support elements 56 used to make up the track supports 18, 20 are shown in FIG. 10. The track supports 18, 20 in transverse cross section can be solid supports of C-, U-, or I-shaped cross section, or even double C- or double U-shaped supports. In a particular embodiment of the invention, the track support element 56 comprises double back-to-back C-sections that are bolted together.

[0054] 9 and 11 can be used to link or join individual track support elements 56 together in both the first and second directions at the junctions where multiple track support elements meet at nodes 52 in the grid structure 50; i.e., the cap plates 58 are used to connect the track support elements 56 together to the vertical uprights 16. As a result, the vertical uprights 16 are interconnected at their upper ends by the cap plates 58 at the junctions where multiple track support elements meet in the grid structure 50; i.e., the cap plates are located at the nodes 52 of the grid structure 50. As shown in FIG. 11 , the cap plates 58 are cross-shaped with four connection portions 60 for connecting to the ends of the track support elements 56 or anywhere along their lengths at the track support element intersections 52. The interconnection of track support elements to the vertical uprights at the nodes by the cap plates 58 is demonstrated in the cross-sectional profile of the node 52 shown in FIG. 13. The cap plate 58 includes plugs or protrusions 62 sized to fit snugly within the hollow central sections 46 of the vertical uprights 16 to interconnect the vertical uprights 16 to the track support, as shown in FIGS. 11 and 12 . The plugs 62 are received within correspondingly shaped openings in the vertical uprights or upright members 16 in a snap-fit ​​arrangement to prevent rotation of the cap plate relative to the vertical uprights 16 about a vertical axis along the longitudinal axis of the vertical uprights. The plugs 62 include downwardly extending resilient members that cooperate to snap-fit ​​into the openings defined by the hollow central opening sections 46 of the vertical uprights. Also shown in FIG. 13 are track support elements 56 a, 56 b extending in both vertical directions corresponding to a first direction (X-direction) and a second direction (Y-direction). The connecting portions 60 are perpendicular to each other to connect to the track support elements 56 a, 56 b extending in the first and second directions. The cap plates 58 are configured to be bolted to the ends of the track support elements 56a, 56b or along the length of the track support elements.Each of the track support elements 56 a, 56 b is positioned to interlock with one another at the nodes to form the grid structure 50 in accordance with the present invention. To accomplish this, the distal or opposing end of each of the tracks of the track support elements 56 a, 56 b is provided with a locking feature 64 for interconnecting with a corresponding locking feature 64 of an adjacent track support element. In a particular embodiment of the present invention, the opposing or distal end of one or more track support elements is provided with at least one hook or tongue 64 that is receivable within an opening or slot 66 located midway through an adjacent track support element 56 at the junction where the track support elements meet within the grid structure 50. Referring back to FIG. 10 in conjunction with FIG. 13, the hook 64 on the end of the track support element 56 is shown received within an opening 66 in an adjacent track support element that extends across the vertical upright 16 at the junction where the track support elements 56 meet. Here, the hook 64 is provided up to the opening 66 on both sides of the track support element 56 b. In a particular embodiment of the present invention, the openings 66 are halfway along the length of the track support elements 56 such that when assembled together, adjacent parallel track support elements 56 in the first and second directions are offset by at least one grid cell. This is demonstrated in FIG.

[0055] To complete the grid structure 50, tracks 22a, 22b are attached to the track support elements 56 after the track supports 56 are interlocked to form a grid pattern with track supports 18 extending in a first direction and track supports 20 extending in a second direction. The tracks 22a, 22b are fitted onto the track supports 18, 20 in a snap-fit ​​and / or slide-fit arrangement (see FIG. 9). As in the track supports according to the present invention, the track comprises a first set of tracks 22a extending in a first direction and a second set of tracks 22b extending in a second direction, the first direction being perpendicular to the second direction. The first set of tracks 22a is subdivided into a plurality of track elements or elongated track elements 68 in the first direction such that adjacent track elements parallel to the first direction are offset by at least one grid cell when assembled together. Similarly, the second set of tracks 22b is subdivided into a plurality of track elements 68 in the second direction such that adjacent track elements in the second direction are offset by at least one grid cell when assembled. This is demonstrated in FIG. 9. An example of a single or elongated track element 68 is shown in FIG. 14, which is contoured to guide a load handling device on the grid structure, typically comprising an elongated element contoured to provide a single track surface to allow a single load handling device to travel on the track, or a dual track to allow two load handling devices to pass each other on the same track. A track surface is defined as the surface on which the wheels of the load handling device roll. When the elongated element is contoured to provide a single track, the track comprises opposing lips or ridges (one lip on one side of the track and another lip on the other side of the track) running along each longitudinal edge of the track to guide or limit the lateral movement of each wheel on the track. For purposes of this invention, the lip or ridge running along each longitudinal edge of the track is defined as a guide surface for restraining the wheels of a load handling device on the track.When the profile of the elongated element is a double track, as shown in the track element in Figure 14, the track has two lips 69a, 69b running along the longitudinal edges of the track and a central lip or ridge 69c running parallel to the lips along the edge of the track, i.e., the track has three parallel ridges. When the two lips or ridges 69a, 69b extend longitudinally along the edges of the track element, the two lips 69a, 69b at the edges of the track element are defined as the first and second edge guide surfaces, respectively. The central lip or ridge 69c is equidistant from each of the lips or ridges at the track edges, so that the area between the central lip and the lips at the edge of the track provides two track surfaces to allow adjacent load handling device wheels to pass each other in both directions on the same track. In the particular embodiment shown in FIG. 14, two lips or ridges 69c are shown extending longitudinally along the central portion of the track, cooperating with lips 69a, 69b at the edges of the track to provide track surfaces on either side of the central ridge 69c. In all cases, the wheels of the load handling device are constrained on either side or both sides of the load handling device wheels when traversing the grid structure. Similar to the track support elements, multiple elongated track elements in the first and second directions are juxtaposed to form track in both directions. The mating portion of the track element 68 to the track supports 18, 20 comprises an inverted U-shaped cross-sectional profile shaped to rest on or overlap the top of the track supports 18, 20. One or more lugs extending from each branch of the U-shaped profile engage the ends of the track supports 18, 20 in a snap-fit ​​arrangement. The track element 68 comprises a notch or recess 70 for accommodating the track support element 56 in the upright column discussed above. Because the track elements 68 are sized to extend or span a single upright in the grid structure, the cutout 70 is formed in the center or midway of each of the track elements 68. It is also contemplated herein that the tracks 22a, 22b may be integrated into the track supports 18, 20 rather than being separate components.

[0056] The grid framework structure 14 can be thought of as a linear assembly of upright columns 16, i.e., a four-walled framework, supporting a grid structure 50 formed from intersecting horizontal grid members 18, 20. Upon receipt of a customer order, a load handling device operable to move on a track is instructed to pick up a storage bin containing the ordered items from a stack within the grid framework structure and transport the storage bin to a pick station, where the items can then be removed from the storage bin and transferred to one or more shipping containers. Typically, the pick station includes a container transport assembly for transporting one or more containers to an access station where the contents of the containers can be accessed. The container transport assembly is typically a conveyor system including multiple adjacent conveyor units.

[0057] In a known fulfillment center, as shown in FIG. 15 , items and stock needed to fulfill a customer order are positioned in containers or storage bins 10, which may be arranged along an aisle. A conveyor system is located on the opposite side of the aisle from the containers or storage bins, and the conveyor system carries customer delivery bins or containers. The conveyor system is arranged to pass a percentage of the delivery bins or containers moving on a backline conveyor through pick stations via station containers, and items ordered by customers are transferred by workers from the storage bins or containers to the customer delivery bins or containers. When a customer delivery container is positioned at a picking station 74 on the conveyor system, the customer delivery container is stopped, and a worker selects the required items from the storage bins or containers and places them in the customer delivery bins or containers. In known robotic picking stations, storage bins or containers are lifted by a load handling device 30 from a stack containing inventory items needed to fulfill a customer order. Once lifted by the load handling device 30, the storage bin or container is delivered by the load handler to an output port 42b above or adjacent to a pick station 74. At the pick station 74, the required inventory item or items may be removed manually or robotically from the storage bin or container and placed into a shipping container which forms part of a customer order and is filled for dispatch at the appropriate time.

[0058] Known fulfillment centers also include various other stations, including, but not limited to, charging stations for charging rechargeable power sources that power the load handling devices on the grid, and service stations for performing routine maintenance on the load handling devices. A separate area 72 is provided adjacent to the grid framework structure 14 to accommodate any one or combination of the stations. Typically, the separate area 72 is provided by incorporating a mezzanine level 76 supported by vertical beams 78 within the adjacent grid framework structure 14, and is a generally freestanding structure. The mezzanine level 76 provides, for example, one or more pick stations and / or a tunnel to accommodate any one of the stations described above. The area below the mezzanine level is typically occupied by personnel working at one or more service stations. Grid structures from the adjacent grid framework structure 14 extend across the top of the mezzanine level 76 to connect to grids on both sides of the mezzanine level 76.

[0059] The grid structure extending across the mezzanine level includes one or more ports 42b for delivering and / or picking up storage containers to and / or from one or more pick stations below the mezzanine level. As taught in the introductory section of this patent specification, a port represents a location or grid cell where a load handling device can drop off and / or pick up a storage container from a pick station below the mezzanine level, allowing the storage container to be accessed from outside the grid or transported into or out of the grid framework structure. The grid column in which a port is located may be referred to as a "delivery column." The storage grid includes two delivery columns. The first delivery column may include, for example, a dedicated drop-off port where a container handling vehicle can drop off a storage container to be transported further through the delivery column to an access station or transfer station, and the second delivery column may include a dedicated pickup port where a container handling vehicle can pick up a storage container transported through the delivery column from the access station or transfer station. Storage containers are delivered to the access station and exit the pick station via the first and second delivery columns, respectively.

[0060] As is apparent from FIG. 15 , the portion of the grid framework structure 14 above the mezzanine level 76 is shallower than the grid framework structures on either side of the mezzanine level 76, i.e., it can accommodate only one or two layers of containers in a stack. The grid structure 14b extending across the mezzanine level is supported by vertical uprights 16 attached to the mezzanine level and is shorter in length than the vertical columns on either side of the mezzanine level. The shorter vertical uprights 16 are sized to accommodate only a small number of containers deep in the stack, e.g., one or more containers deep, to ensure that the grid structure lies in a substantially horizontal plane as it extends across the mezzanine level, i.e., that the grid level is maintained across the mezzanine level. The mezzanine level 76 is supported by separate vertical beams 78. The vertical beams 78 supporting the mezzanine level 76 abut the grid framework structure 14 on either side of the mezzanine level 76. Multiple stacks of storage containers are stored in the vertical storage columns on either side of the mezzanine level. A robotic load handling device operable on the grid structure can retrieve storage containers from one or more of the vertical storage columns and transport the storage containers above the mezzanine level, where the load handling device can deliver the storage containers to a pick station below the mezzanine level. As a result, the grid structure can be divided into different regions. To differentiate between the grid structure extending above the mezzanine level and the grid structure extending over the multiple storage columns, the grid structure extending above the mezzanine level can be referred to as a first region of the grid structure, and the grid structure extending over the multiple vertical storage columns on either side of the mezzanine level can be referred to as a second region of the grid structure. Similarly, to differentiate between the multiple upright members supporting the first region of the grid structure above the mezzanine level and the multiple upright members supporting the second region of the grid structure, the multiple upright members supporting the first region of the grid structure can be referred to as a first set of upright members, and the multiple upright members supporting the second region of the grid structure can be referred to as a second set of upright members.Because the storage containers are stored in stacks below the grid structure in the second area, the second set of uprights making up the vertical storage columns are longer than the first set of uprights supporting the first area of ​​the grid structure above the mezzanine level.

[0061] An exploded view of a section of the grid framework structure within a junction area 84 between the mezzanine level and the vertical storage columns is shown in FIG. 16, and a top plan view of the grid structure highlighting the first and second regions of the grid structure is shown in FIG. 17. The junction area 84 illustrates the difference in the lengths of the uprights 16, 16b that support the first and second regions 80, 82 of the grid structure 14. The shorter uprights 16b, referred to as the first set of uprights, are positioned to extend above the mezzanine level (not shown), while the second set of uprights are positioned to form a plurality of vertical storage columns 44 for storage of storage containers in a stack. Due to the length of the uprights 16 that make up the vertical storage columns 44 compared to the length of the uprights 16b that extend above the mezzanine level, the longer second set of uprights 16 are more likely to move than the shorter first set of uprights. During ground movements, particularly during a seismic event, the longer second set of uprights 16b vibrate with a greater amplitude than the shorter first set of uprights 16a. Vibrations of the grid framework structure comprising vertical storage columns 44 are exacerbated by the stacks of storage containers stored within the vertical storage columns. Bending moments generated in second region 82 of the grid structure as a result of vibration of the longer second set of uprights 16b are transferred to first region 80 of the grid structure, which extends above the mezzanine area. The greater the amplitude of vibration of the second set of uprights, the greater the risk of failure of the grid member interconnections where the grid members meet at nodes within first region 80 of grid structure 14b. Because the uprights are interconnected to the grid members by one or more fasteners and by connecting or cap plates at the nodes of the grid structure, as discussed above, the connections between the grid members at the nodes could become loose and, in a worst-case scenario, be lost, resulting in grid structure components, particularly in the first region 80 above the mezzanine area, at risk of becoming dislodged and falling into the service area. Because people work in the service area, loss of the connections interconnecting the grid members to the uprights (first set of uprights) in the first region poses a risk of injury to people working in the service area below. Mechanical fuse The present invention alleviates this problem by creating a point of weakness within the grid structure that preferentially fails to separate different regions of the grid structure, thereby preventing bending moments from being transferred from one region of the grid structure to another region of the grid structure. In the particular embodiment shown in the top views of FIGS. 16 and 17 , the point of weakness 86 is preferentially located within the junction area 84 where different regions of the grid structure meet, i.e., between the first region 80 and the second region 82. The point of weakness 86 is configured to preferentially fail when a tensile force acting on the point of weakness in a predetermined direction exceeds or equals a predetermined load, but does not necessarily fail other connections of the grid members within the grid structure, i.e., the interconnections 52 between the upright members and the grid members via the cap plate 58, for example. In other words, the point of weakness is configured to fail under an applied load, but not necessarily fail the interconnections between the upright members and the grid members. The predetermined direction is parallel to the longitudinal direction of the grid members 18, 20 within the joining area 84 between the first and second regions 80, 82 of the grid structure 14b, as indicated by the arrow in FIG. 17. This may be along the X-direction or the Y-direction, depending on the orientation of the grid members within the grid structure. To preferentially create the weak points within the grid structure, the predetermined load to break the weak points needs to be less than other connections of the grid members within the grid structure. The other connections are more specifically at the interconnections 52 between the upright members and the grid members as discussed above, i.e., via the cap plate 158.

[0062] In a specific embodiment of the invention shown in FIG. 18 , the weak point in the grid structure is provided by a bridging joint assembly 88 comprising a mechanical fuse 90 configured to break when an applied load exceeds or equals a predetermined load. The bridging joint assembly 88 is positioned as one or more connections between a first region of the grid structure and a second region of the grid structure (see FIG. 19 ). Because the wheel assemblies of the robotic load handling device include pairs of wheels at the front and rear of the vehicle body and pairs of wheels on either side of the wheel body (see FIG. 4 ), the bridging joint assembly 88 is positioned as one or more pairs of connections between the first region and the second region of the grid structure, i.e., between the first set of grid members and the second set of grid members. An example of a bridging joint assembly 88 according to the present invention is shown in FIG. 18 . The example bridging joint assembly 88 shown in FIG. 18 includes a bracket 92 configured to connect the free ends of adjacent grid members 18, 20. The other end of each adjacent grid member is connected to a respective cap plate 158 by one or more bolts as shown in Figure 18 for interconnection to adjacent upright members in the grid structure. Adjacent grid members connected together by bridging joint assemblies 88 function as a single elongated grid element extending between adjacent upright members in the grid structure.

[0063] Tracks 22a, 22b are positioned on each adjacent grid member such that when the ends of adjacent grid members are connected together by a bridging joint assembly of the present invention, a continuous track surface extends across the ends of the adjacent grid members (see FIG. 19). This allows the wheel assemblies of the robotic load handling device to roll across the bridging joint assembly of the present invention. In the particular embodiment of the present invention shown in FIG. 18, the grid members function as track supports, and separate track elements are attached to the track supports, for example, in a snap-fit ​​arrangement.

[0064] The brackets 92 joining the ends of adjacent grid members are in the form of plates that overlap the ends of the adjacent grid members. In the particular example shown in the cross-sectional view of the bridging joint assembly shown in FIG. 20, two brackets are shown on either side of the ends of the grid members to clamp the ends of the adjacent grid members together. The opposing, or free, ends of the brackets are connected to the ends of the adjacent grid members by one or more fasteners, such as bolts, screws, or pins, that are received in openings in the ends of the grid members, within the joint area where they overlap the ends of the adjacent grid members. The one or more fasteners are positioned to break when an applied load exceeds or equals a predetermined load, separating the ends of the adjacent grid members and thereby preferentially separating different regions of the grid structure (see FIG. 21). In the particular example shown in FIG. 20, the mechanical fuse 90 comprises a shear pin 94 having a failure zone 96, the failure zone comprising a reduced cross-sectional area or neck portion of the pin that is positioned to shear when an applied load on the failure zone exceeds or equals a predetermined load. In the particular example shown in FIG. 20, the mechanical fuse comprises two shear pins 94 linked together by a linkage 98 so that when the pins break, the linkage holds the shear pins together.

[0065] To prevent other connections in the grid structure, such as the interconnections between uprights and grid members, from breaking loose under a predetermined load, the predetermined load for breaking the mechanical fuse is set to be less than the load of the interconnections between multiple uprights and grid members in the grid framework structure. Vibration of the grid frame structure as a result of ground movement generates tension forces on the bridging joint assemblies that link different regions of the grid structure together. When the tension force exerts a load on the bridging joint assemblies that exceeds or equals the predetermined load for breaking the shear pin, at least one end of the bracket 92 separates from its connecting end of the grid member; i.e., the tension force is less than the load holding the grid members together in the grid structure at their interconnections with the uprights. This is demonstrated in the schematic diagram shown in FIG. 21 , which illustrates the separation of the ends of grid members 18 and 20. The mechanical fuse 90 can include one or more shear pins for connecting the bracket 92 to the ends of the grid members. In the specific embodiment shown in FIG. 18 , at least two fasteners at each end of the bracket are used to connect the bracket to the ends of the grid members. Thus, to separate the ends of the grid member, at least two of the fasteners shear under a predetermined load to separate the bracket from at least one end of the grid member.

[0066] While mechanical fuses 90 comprising one or more shear pins are positioned to connect the brackets to the ends of adjacent grid members, other means for providing preferential points of weakness within the grid structure comprising mechanical fuses are equally applicable to the present invention. For example, one or more fasteners used to interconnect the upright members to the grid members via a connecting plate or cap plate can function as mechanical fuses. For example, one or more bolts connecting the grid member to the connecting portion 60 of the cap plate 158 can be fabricated with a failure zone configured to shear under an applied load exceeding or equal to a predetermined load to disconnect the grid member from the connecting portion, and thus the cap plate (see FIG. 9). In the specific example of the present invention shown in FIG. 18, at least two fasteners 100 are used to connect the ends of the grid members to the cap plate. Two such fasteners can be fabricated as mechanical fuses configured to shear when the load exceeds or equals a predetermined load. Other means of incorporating points of weakness in a grid structure with mechanical fuses include fabricating grid members with failure zones, e.g., reduced cross-sectional areas, such that portions of the grid members break when a tensile force exceeds or equals a predetermined load. Similarly, brackets that connect ends of adjacent grid members may themselves be provided with failure zones configured to break under an applied load that exceeds or equals a predetermined load. In all of the different examples, the points of weakness with mechanical fuses are configured to preferentially isolate different regions of the grid structure during ground movement, e.g., a seismic event.

[0067] Although the mechanical fuses are configured to preferentially isolate different regions of the grid structure, movement of the grid frame structure is unavoidable during a series of movements of the grid frame structure in a fulfillment center. For example, temperature changes in the environment in which the grid frame structure is located can cause different portions of the grid frame structure to expand and contract as a result of thermal expansion. Without measures to account for thermal expansion, there is a risk that regions of the grid structure may distort or buckle as one or more grid members expand or contract in length, increasing the likelihood of one or more robotic load handling devices operable on the grid structure becoming dislodged.

[0068] In the specific example shown in Figures 22(a-c), opposing ends of a bracket 92 of a bridging joint assembly 88 are connected to the ends of adjacent grid members 18, 20 with a sliding connection. The sliding connection between the bracket 92 and the ends of the grid members comprises one or more sliding members comprising bolts or pins arranged to slide along slots 102 formed in the ends of adjacent grid members to allow the separation between the ends of the grid members to change longitudinally, i.e., in the X or Y direction. The cooperation of the sliding bolts and slots 102 is clearly shown in Figure 21. The length of travel of the ends of the grid members is determined by the length of the slots 102, and the opposing ends of each slot 102 function as stops to prevent further separation of the ends of the grid members. When one or more bolts extending through the slots reach their end of travel determined by the slot length, the ends of the grid members are prevented from further movement. The bolt or bolts extending through the slots may each be provided with a sliding bearing 104 (see FIG. 21), or alternatively, a roller bearing, to assist the bolt in sliding along the slot. While the sliding connections in the particular embodiment shown in FIGS. 22(a-c) show slots formed in the ends of the grid members, the reverse is also true, where slots are formed in brackets joining the ends of the grid members together, and bolts fastening the brackets to the ends of the grid members are positioned to slide along slots in the brackets.

[0069] Different stages of separation of the ends of grid members 18, 20 are shown in Figures 22(a) through 22(c). Figure 22(a) shows the ends of the grid members in a closed configuration, and Figures 22(b) through 22(c) show different stages of separation of the ends of the grid members as adjacent grid members move longitudinally to a maximum extent determined by the length of the slot 102. One or more bolts extending through the slot 102 can function as a mechanical fuse 94 configured to break when a tensile force acting on the bridging joint assembly exceeds or equals a predetermined load to separate different regions of the grid structure. The length of the slot, and therefore the separation of the ends of adjacent grid members, is calculated based on the level of movement of the grid members as a result of expansion and contraction of the grid members. Typically, during normal operation, the length of the slot allows movement of the grid members in either the X or Y direction as a result of thermal expansion and contraction, ranging from about 10 mm to about 180 mm of movement. If movement of the grid structure creates a tensile force that would move the grid members beyond a predetermined length, the ends of the slots prevent such further movement of the grid members. However, when the tensile force on the bridging joint assembly exceeds or equals a predetermined load, the bolts are configured to break upon reaching the ends of their respective slots 102, thereby severing the ends of the grid members and allowing various regions of the grid structure to be separated. In the particular embodiment of the invention shown in Figures 21 and 22, the grid members connected by brackets 92 are I-beams. Slots 102 are formed at the ends in the I-beams that cooperate with mechanical fuses 94 that fasten the brackets 92 to the ends of the grid members.

[0070] To provide a continuous track surface on the grid members 18, 20 when the grid member ends separate, the bridging joint assembly 88 further includes an expansion joint comprising a first track element 106 and a second track element 108, and a bridging member 110 extending across the ends of the first and second track elements 106, 108. The first track element 106 is positioned at one end of the adjacent grid member, and the second track element 108 is positioned to overlap the other end of the adjacent grid member. The bridging member 110 extends across the ends of the first and second track elements 106, 108. Each of the first and second track elements and the bridging member 110 represent at least a portion of a single elongated track element. Thus, the first and second track elements and the bridging member have respective interface portions contoured to mate to form a single elongated track element that provides a continuous track surface.

[0071] The upper surface of the bridging member 110 is contoured to provide a transition along the expansion joint from the first track element to the second track element. In the specific example shown in Figures 23(a) and 23(b), the contours of the first and second track elements provide a dual track with a central ridge and tracks on either side of the central ridge. The upper contour of the bridging member 110 is shown as two track or rolling surfaces 110a, 110b extending longitudinally across the distal end of the grid member. The track surfaces of the bridging member 110 are positioned to provide rolling surfaces for the wheels of the robotic load handling device. The rolling surfaces of the track surfaces extend across the width of the wheels of the robotic load handling device. The bridging member 110 has a first end 112 fixed to the first track element 106 and a second end 114 that can rest along a groove 116 formed in the second track element 108. For example, the second end 114 of the bridging member 110 comprises a sliding anchor 118 constrained to move along a guide 116 comprising a groove formed in the second track element, as shown in FIG. 24. Also shown in FIG. 24 is the sliding anchor 118 extending through a groove in the end grid members 18, 20 that support the second track element. When the ends of adjacent grid members separate, the bridging member 110 spans the gap created between the ends of the adjacent grid members. In the particular example shown in FIG. 23b, the second end 114 of the bridging member 110 is positioned to overlap the second track element 108.

[0072] However, other means for spanning the gap between the first and second track elements when the ends of adjacent grid members separate to provide a continuous track surface are applicable to the present invention. In the example shown in FIG. 25 and incorporated into a grid structure in FIG. 26, the bridging member 110 may be formed as a protruding male portion 110c of the first track element that is received in a correspondingly shaped recess 108b in the second track element 108. The bridging member 110 is shown in FIG. 25 as integrally formed with the first track element 106 as a protruding male portion, while the second track element includes a receiving female portion 108b. Compared to the bridging member 110 shown in FIGS. 23(a and b), in which the track surfaces 110a, b of the bridging member 110 extend across the width of the wheel, in the example shown in FIG. 25, the track surface of the bridging member formed as a protruding male portion 110c only contacts at least half the width of the wheel as the wheel traverses across the bridging member 110. The other half of the wheel width does not contact the track surface of the protruding male portion 110c. The robotic load handling device is prevented from derailing by the wheel pairs being restrained on either side of the vehicle body. This can be demonstrated by the schematic diagram shown in FIG. 27, which shows two robotic load handling devices 30a, 30b side-by-side on a track provided by a set of parallel bridging members 110 of the present invention, each bridging member 110 having a central lip or ridge 110d for restraining only one side of each wheel 34. Because each robotic load handling device comprises a pair of wheels 34 at the front and rear of the vehicle body, restraining only at least one side of the wheels prevents lateral movement of the robotic load handling device on the track, thereby preventing the robotic load handling device from derailing. In the particular example shown in FIG. 27, the outer edges of the wheels of the load handling device are restrained by abutting the central ridge 110d of the bridging member 110 when the ends of the adjacent grid members separate.

[0073] Typically, the bridging member 110 is a relatively thin strip of metal configured to span the ends of the first and second track elements 106, 108 when the ends of adjacent grid members separate to provide a continuous track surface across the ends of the first and second track elements. Given that a robotic load handling device operable on the track can weigh over 100 kg, there is a risk that the bridging member 110 will bend under the weight of the robotic load handling device traveling across the bridging member 110. To prevent the bridging member from bending under the weight of the robotic load handling device operable on the track, the bridging joint assembly further includes a support 120 intermediate the ends of the first and second track elements 106, 108 (see FIGS. 25 and 26). The upper end of the support 120 is contoured to rest on the bridging member 110 when the ends of adjacent grid members separate (see FIGS. 25 and 26). In the particular embodiment shown in Figure 25, the supports 120 are secured to the brackets 92 by one or more bolts that join the ends of adjacent grid members together. The supports 120 are shown secured to the brackets 92 midway between the ends of the first and second track elements 106, 108 so that when the ends of the grid members are brought together as shown in Figure 22a, the ends of adjacent grid members abut the supports 120 such that the supports act as spacers between the ends of adjacent grid members.

[0074] In the specific example shown in Figures 16 and 17, the same type of grid members make up the grid structure, such that the interconnections between the upright members and the grid members are primarily provided by the same type of cap plates. In other words, the bridging joint assemblies of the present invention used to connect different regions of the grid structure comprise the same type of grid members. In this specific example shown in Figure 16, the grid members comprise back-to-back C-sections having a substantially I-shaped cross-sectional profile. Using such grid member types to interconnect the upright members that make up the vertical storage columns ensures that the grid framework structure can handle small changes in ground movement characteristic of Type A or B earthquake events, but the same cannot be said for large changes in ground movement characteristic of Type D earthquake events. To accommodate the large deflections in the grid framework structure characteristic of Type D earthquake events, the grid members that make up the grid structure need to be stronger in terms of bending stiffness.

[0075] In the specific example of the present invention shown in FIG. 28, the grid members 18, 20 that make up the grid structure region comprise tubular beams 122, most of which have a cross section with a hollow center section. The use of tubular beams 122 to construct the grid members, compared to beams of other shapes, provides greater resistance to bending because the walls of the tubular beams 122 can resist bending in all directions. The tubular cross-sectional profile of the grid members provides resistance to bending moments in multiple directions. To further improve the structural rigidity of the grid members against bending, the wall thickness of grid members constructed as tubular beams is much greater than that of grid members in the Type A or B grid structures discussed above. Furthermore, compared to bolted grid members at intersections where grid members meet, which are prone to loosening during a strong seismic event, the grid members are preferably welded at the intersections 52. The welded joints at the intersections 52 provide stronger, more rigid joints where grid members meet. When bending moments are transferred to the intersections, the welding of the grid members at the intersections 52 means that the joints are better able to resist loads at the intersections.

[0076] The grid structure is subdivided into a plurality of subframes as shown in Figures 29 and 30, whereby one or more of the subframes 124 comprise at least one grid cell 42. The subframes 124 are assembled together when the grid structure is erected on-site. To comply with building regulations, ideally, the individual subframes are bolted together as they are erected on-site. The ends of the grid elements that make up a subframe include connecting portions 125 that are positioned to mate with corresponding connecting portions of adjacent subframes. The connecting portions 125 include one or more holes for receiving bolts.

[0077] Separate track support elements 126 a, 126 b are attached directly to the grid element 122 to provide tracks or rails for load handling devices to travel on the grid (see FIG. 31 ). The track support elements 126 a, b allow tracks or rails 128 a, b to fit onto the grid element 122. A plurality of track support elements 126 a, b are distributed on the grid element 122 of the subframe 124 having a contour shaped to accept the tracks. Thus, compared to the grid elements of the grid framework structure discussed above in which the track support elements are incorporated within the grid elements of the grid (back-to-back C-shaped sections having contours to accept the tracks by a snap-fit ​​arrangement), the track support elements 126 a, b of the seismic grid framework structure are separate from the grid elements 122. Figure 29 shows a top view of a subframe 124 according to an embodiment of the invention showing X- and Y-extending track support elements 126a,b mounted directly to the tubular grid elements 122, and Figure 31 shows a cross-sectional view of the subframe showing the engagement of the tracks 128a,b with the grid members 18, 20 by the track support elements 126a,b according to an embodiment of the invention. Like the tracks mounted to the grid elements of the grid framework structures discussed above, the tracks 128a,b are fitted to the grid elements 122 in the seismic grid framework structure via the track support elements 126a,b by a snap-fit ​​and / or slide-fit arrangement.

[0078] When the seismic grid framework structure of the present invention does not have cap plates to join the grid elements together because the grid elements are welded together at their intersections, plugs 162 for connecting the upright columns 16 are attached directly to the underside of the subframe 124 at the joints where the grid members meet to interconnect the vertical upright members to the grid of the seismic grid framework structure of the present invention (see FIG. 30 ). In a specific embodiment of the present invention, the plugs 162 are welded to the underside of the subframe at the joints where the grid members 18, 20 meet, i.e., at the nodes of the grid structure. As shown in FIG. 30 , four plugs 162 are seen attached directly to the underside of the subframe 124 at the intersections where the grid members 18, 20 meet. However, other structural bending-resistant beams can be used to increase the structural rigidity of the grid structure. These include, but are not limited to, I-beams.

[0079] Type D grid structures are more suitable when the grid members of the grid structure are subject to increased bending moments and stresses due to ground movement. Because the grid members above the vertical storage columns are subject to increased bending moments due to the height or length of the vertical uprights for storing multiple storage containers in a vertical stack, the grid members comprising the grid structure above the vertical storage columns tend to be constructed from more bending-resistant beams, such as tubular beams as discussed above. However, other regions of the grid structure, i.e., the region above the mezzanine level, do not necessarily need to have the same level of structural rigidity as the grid structure above the vertical storage columns and can be based on less bending-resistant beams, such as back-to-back C-sections as discussed above. This is exemplified in the section of a grid framework structure shown in Figure 32, where different regions 80, 82 of the grid structure are constructed from different types of grid members 18, 20. However, a problem with having different regions 80, 82 of a grid structure have grid structures with different levels of structural rigidity is that the structurally rigid grid structure has the potential to topple, or at least cause substantial damage to, the weaker grid structure during a strong seismic event characteristic of a Type D earthquake event. Bridging joint assemblies of the present invention can link different regions of a grid structure even when each region of the grid structure comprises different types of grid members. In the specific example shown in FIG. 32 , a bridging joint assembly of the present invention is used to link region 82 of the grid structure comprising tubular beams 122 with region 80 of the grid structure comprising back-to-back C-sections. However, the bridging joint assembly 88 of the present invention is not limited to the grid member types shown in FIG. 32 and may be used to link together any type of grid member from different regions of a grid structure.

[0080] For ease of explanation, the grid structure comprising the weaker grid members may be referred to as the first region 80 of the grid structure 14b, and the grid structure comprising the more structurally robust grid members may be referred to as the second region 82 of the grid structure 14b. The grid members comprising the first region 80 of the grid structure may be referred to as a first type of grid member and may correspond to the grid members shown in FIG. 10. Similarly, the grid members comprising the second region 82 of the grid structure may be referred to as a second type of grid member and may correspond to the grid members shown in FIG. 28. Because the grid members comprising the first and second regions 80, 82 of the grid structure 14b differ in terms of shape and size, different brackets 158, 130 are required to incorporate the bridging joint assembly 88 of the present invention to connect the first and second regions 80, 82 of the grid structure 14b together. The different brackets 158, 130 connecting the different regions 80, 82 of the grid structure 14b together are necessary to ensure that the grid level remains horizontal across the different regions of the grid structure. Bridging joint assemblies 88 are positioned to connect the ends of adjacent grid members extending between the first and second regions of the grid structure, as shown in FIG. 33. The other end of each adjacent grid member is connected to its upright member by a first type bracket 158 ​​and a second type bracket 130 to compensate for the difference in height of the grid members comprising the first and second regions 80, 82 of the grid structure. For ease of explanation, adjacent grid members connected together by the bridging joint assemblies of the present invention to form an elongated grid element may be referred to as first and second portions of the grid member linking the first and second regions of the grid structure. Thus, the first region of the grid member is connected to the upright member by the first type bracket 158, and the second portion of the grid member is connected to the adjacent upright member by the second type bracket 130.In the particular example shown in FIG. 33 , the first type of bracket is a cap plate 158 because the grid members in the first region of the grid structure are generally back-to-back C-sections, i.e., first type grid members. However, the grid members in the second region of the grid structure are different because they need to be structurally more resilient to ground movement. Therefore, the second type of bracket 130 includes a post or spacer 132 having an upper end 134 connected to the end of the second portion of the grid member and a lower end 136 connected to the upright member to accommodate the height difference between the grid members in the first region of the grid structure and to ensure that the track remains horizontal within the grid structure. The post or spacer 132 compensates for the height difference between the grid structure in the first region and the grid structure in the second region. The grid members in the second region of the grid structure are generally tubular with a hollow cross-sectional profile, i.e., second type grid members, as shown in FIG. 28 . In all cases, the bridging joint assembly 88 behaves in the same manner as discussed above, in this case the mechanical fuse 90 is configured to preferentially fail when the tensile force acting on the mechanical fuse exceeds or equals a predetermined load required to separate a first region of the grid structure from a second region of the grid structure.

[0081] Two-way expansion joint The expansion joints, including the first and second track elements 106 and 108 and the bridging members 110 extending across the ends of the first and second track elements, can only compensate for grid member movement in the longitudinal direction (indicated by the arrows in FIG. 34 ), and therefore can only accommodate movement in either the X or Y direction. To compensate for grid member movement in both the X and Y directions, separate expansion joints are required to link the ends of adjacent grid members extending in the X and Y directions to accommodate both longitudinal movements. To compensate for grid member movement in both the X and Y directions in the present invention, at least one of the upright members is interconnected to the grid member by a connection comprising a pivotable joint, thereby allowing the grid member to rotate in a horizontal plane about a vertical axis extending through the pivotable joint. When the grid member is connected to the upright member by a bracket, in this case a cap plate 158, a pivotable connection exists between the cap plate and the end of the grid member, as demonstrated in FIG. 34 . As discussed above, the cap plate 158 is restricted from rotational movement by a bung 62 received in a correspondingly shaped hollow central section 46 of the vertical upright or member 16 that extends downwardly from the cap plate. The pivotable connection is provided by a bolt or bearing member extending through an opening 238 in the connecting portion of the cap plate 158, as shown in FIG.

[0082] As the grid members move as a result of expansion and / or contraction of the grid members, the pivotable connections can accommodate movement of the grid members in either the X or Y direction. Longitudinal movement is accommodated by the sliding relationship of the track elements 106, 108 discussed above. To incorporate movement in both the X and Y directions, at least one end of a grid member in a grid structure connected or joined together by a bridging joint assembly of the present invention is pivotally connected to its respective upright member.

[0083] To better illustrate the concept of a pivotable joint together with the sliding relationship of the track elements to accommodate movement in both the X and Y directions, the relationship between the pivotable connection of the grid members and the sliding connection of the track elements positioned on the grid members is best described with reference to a first upright member 16a and a second upright member 16b (see FIG. 32) interconnected by a grid member extending between both upright members, as shown in FIGS. 34 and 35. In the particular example shown in FIG. 34, the ends of adjacent grid members extending between the first and second upright members are connected together by a bridging joint assembly 88 of the present invention to enable movement of the grid members in the longitudinal direction. The first upright member is interconnected at its upper end to the grid member by a connection comprising a pivotable joint, whereby upon movement of one of the first or second upright members relative to the other of the first or second upright members, the grid member is rotatable in a horizontal plane about a vertical axis extending through the pivotable joint. In the particular example shown in FIG. 34 , the ends of adjacent grid members 18, 20 extending between a first upright and a second upright are pivotally connected to their respective uprights to allow movement of one of the first or second uprights relative to the other. Rotation of the grid members causes corresponding rotational movement of track elements 106, 108 positioned on the grid members, as demonstrated in the schematic diagrams of portions of the grid structure shown in FIGS. 36 and 37 . This allows the tracks 22 a, b to move laterally when subjected to forces in the X or Y directions. In the particular example shown in FIG. 36 , the tracks are allowed to move laterally in a horizontal plane in the X direction.

[0084] To accommodate longitudinal movement, the joint between the ends of adjacent grid members comprising the first and second track elements 106, 108 and the bridging member 110 extending across the first and second track elements allows one end of the bridging member to slide longitudinally (see FIG. 36), in this case in the Y direction. Thus, rotational movement of the connected grid members by the pivotable joint allows movement of a portion of the grid structure in the X direction, and the bridging joint assembly connecting the ends of the grid members together allows longitudinal movement in the Y direction; i.e., both the X and Y directions can be covered by a single thermal stretch extending between adjacent vertical or upright members.

[0085] As a result of the pivotable joints connecting the grid members to the uprights, movement of one of the first or second upright members relative to the other of the first or second upright members displaces the track elements relative to the adjacent track elements in the area where the track elements intersect at nodes 52 of the grid structure. This displacement causes misalignment of the upper track contour, particularly at the nodes, as demonstrated in FIG. 37. If rotation of the grid members, and therefore the corresponding track, becomes too excessive to interrupt the continuous track surface in the junction area where the track elements meet at a node in the grid structure, the wheels of the robotic load handling device risk derailing as they intersect the intersection of the track elements. To prevent excessive misalignment of the track elements as a result of rotation of the grid member about its pivot connection with the uprights, the pivot joint is limited to rotating a predetermined angle from its center or nominal position, where the predetermined angle is small enough to allow the wheels of the robotic load handling device to traverse across the misaligned track elements. The pivotable joint is limited to a predetermined angle of rotation by providing a stop member arranged to rotate within an arcuate slot having a radius of curvature about the pivotable joint. As shown in FIG. 38, in addition to an opening 238 in the connecting portion of the cap plate 158 for accommodating the pivotable joint between the end of the grid member and the cap plate, the connecting portion of the cap plate 158 further includes at least one arcuate slot 140 through which a stop member 142 (see FIG. 35) extends, thereby allowing the grid member connected to the cap plate 158 by the pivotable joint to rotate through a predetermined angle defined by the arc of the arcuate slot 140. In the specific embodiment shown in FIGS. 42(a and b), the stop member 142 includes a shear pin 146 having a breaking zone 96. The predetermined angle can be in the range of 1° to 20°, preferably in the range of 5° to 20°. In operation, the stop member 142 received within the arcuate slot 140 is positioned to be guided by the arcuate slot 140 up to a limit determined by the ends of the arcuate slot 140 .The grid member is prevented from further rotation when the stop members 142 abut against opposite ends of the arcuate slots 140. In the particular embodiment shown in FIG. 38, two arcuate slots 140 are shown in the cap plate / bracket connection disposed laterally on either side of the pivotable joint, i.e., shown as opposing arcuate slots 140. Each of the arcuate slots 140 defines an arc having a radius of curvature centered about the pivotable joint within which a stop member 142 is received.

[0086] The pivotable connection between the grid member and the upright member is not limited to the first type bracket with a cap plate 158 as shown in FIG. 38 , but can also be provided between the second type bracket 130 and the Type D grid member discussed above, i.e., the connection with the second type grid member ( FIGS. 33 and 39 ). Here, the top connection portion 134 of the second type bracket 130 includes an opening 338 for accommodating the pivotable joint and an arcuate slot 240 having a radius of curvature centered on the pivotable joint. The bottom connection portion 136 of the second type bracket 130 is fixed to the upright member. Using the terminology discussed with reference to FIGS. 34 and 35 , the bottom connection portion 136 of the second type bracket 130 is fixed to the second upright member 16 b. In the specific example of the invention shown in FIG. 32 , the first upright member 16 a is shorter than the second upright member 16 b. As a result, ground movement, for example, during a seismic event, tends to cause the longer second upright members 16b to vibrate at a greater amplitude than the shorter first upright members 16a. As discussed above, to compensate for the difference in the amplitude of vibration of the first and second upright members 16a and 16b, the Type D grid members or second type grid members interconnecting the second upright members 16b within the second region of the grid structure are configured to provide greater structural integrity or rigidity during ground movement than the first type grid members. As a result, the cross-sectional contours of the second type grid members are sized differently, e.g., larger, than the cross-sectional contours of the first type grid members. The second type brackets 130 compensate for the size difference between the first and second type grid members such that when a first region of the grid structure comprising the first type grid members is linked or connected to a second region of the grid structure comprising the second type grid members, the grid structure remains substantially horizontal.

[0087] By adjusting the type of brackets used to interconnect the uprights to the grid members within the grid frame structure, a first upright member can be laterally displaced relative to a second upright member through the pivotable connection between the grid member and its respective upright member, regardless of the type of bracket used to connect the grid member to the upright member (see Figures 40 and 41). Thus, longitudinal grid member expansion and contraction is effected by movement of the first track element 106 relative to the second track element 108. Brackets 92 maintain the connection between the ends of the grid members supporting the first and second track elements 106, 108. Movement perpendicular to the longitudinal direction is effected by rotation of the grid members 18, 20 relative to the upright members to which they connect, via the second type of brackets 130.

[0088] In the unlikely event that the force to rotate the grid member exceeds a predetermined load characteristic of a seismic event, the stop member 142 can function as a mechanical fuse arranged to break when an applied load in a first or second direction generates a rotational force that exceeds the failure point of the mechanical fuse. An example of a stop member 142 with a failure zone 96 is shown in Figures 42(a and b), where Figure 42(a) shows the stop member 142 in an intact state and Figure 42(b) shows the stop member 142 in a broken state, thereby allowing the grid member to rotate beyond the arc defined by the arcuate slot. Also shown in Figures 42(a and b) is an optional linkage 144 of the stop members on either side of the pivot joint to allow the shear pins 146 to move together within their respective arcuate slots 240 (see Figure 39). Cross sections along line XX in FIG. 40 of a pivotable connection between an upright member and a grid member incorporating stop members 142 received in their respective arcuate slots 240 on either side of the pivot joint are shown in FIGS. 43 and 44. When a force substantially perpendicular to the longitudinal direction of the grid member is applied, causing the rotation angle of the grid member to exceed a predetermined angle determined by the arc of the arcuate slots 240, the mechanical fuse 94 of the stop members 142 breaks, allowing the grid member to rotate further to compensate for the movement of the grid member. This is demonstrated in the cross section of the pivotable connection between the grid members 18, 20 and the upright members shown in FIG. 44. To compensate for the effects of external forces that distort the grid structure and cause damage to the grid members and tracks, the mechanical fuse 94 connecting the grid members to the upright members preferentially breaks, allowing the grid member to rotate. In other words, the mechanical fuse 94 provides a sacrificial element in the grid structure that preferentially breaks to prevent or mitigate significant distortion of the grid structure. Where one or more interconnections of the upright members with the grid member comprise pivotable joints, the mechanical fuse allows a first region of the grid structure to move relative to a second region of the grid structure about the one or more pivotable connections.The effect of rotating adjacent grid members between first and second regions of the grid structure as a result of a broken mechanical fuse is demonstrated in the schematic diagram shown in FIG. 45. Here, track elements 106, 108 of bridging joint assembly 88 are rotated beyond a predetermined angle, resulting in significant misalignment of the upper contours of the track elements relative to adjacent tracks at the nodes of the grid structure. In the example shown in FIG. 45, rotational movement of the track elements by the pivotable joint results in misalignment of track elements 106, 108 relative to tracks 22a, 22b at the nodes of the grid structure. Breaking of the mechanical fuse as a result of ground movement characteristic of a seismic event protects different regions of the grid structure from further damage and also prevents regions of the grid structure from causing injury from falling debris below the grid structure, particularly to people below the mezzanine level.

[0089] While the track elements of an expansion joint each have an interface or mating portion that allows the track elements to connect to each other to form the single elongated track element discussed above, the expansion joint relies on having differently shaped components to mate the first and second track elements together. In other words, the interface portions of each track element of the expansion joint have differently shaped mating contours, such that a single track element is formed when the differently shaped mating contours mate at their respective interface portions. For example, in the thermal expansion joint embodiment shown in FIG. 25, in which the bridging member 110 is formed as a protruding male portion 110b of the first track element that is received in a correspondingly shaped recess 108 in the second track element 108, the first and second track elements need to be shaped differently to connect together to form a single elongated track element.

[0090] In another embodiment of the invention shown in FIG. 46, the interface portions 210a, b of the first and second track elements 206, 208 are shaped such that the interface portion 210b of the second track element 208 is a 180° rotation about the vertical axis of the interface portion 210a of the first track element 206. In other words, the interface portion 210a of the first track element 206 is a duplicate of the interface portion 210a of the second track element 210, but rotated exactly 180° about the vertical axis to allow the interface portions 210a, b of the first and second track elements to mate with each other to complete the dual track surfaces 110a, 110b as shown in FIG. 47(a-c), i.e., to complete a single elongated track element extending in either the first or second direction. This has the advantage that only a single shaped track element is required for both the first and second track elements, which further reduces equipment costs in fabricating thermal expansion joints. Because the first orbital element 206 and the second orbital element 208 correspond to at least a portion of a single elongated orbital element, the first orbital element can be defined as the first orbital element portion and the second orbital element can be defined as the second orbital element portion. Accordingly, FIG. 46 shows the first orbital element portion 206 and the second orbital element portion 208 connecting to each other at their respective interface portions to form the single elongated orbital element. In the specific embodiment of the invention shown in FIG. 46, the first and second orbital element portions are substantially identical but rotated exactly 180° about a vertical axis. FIGS. 47(a-c) show the first orbital element portion 206 and the second orbital element portion 208 being brought together to form a single elongated orbital element extending in either a first direction or a second direction.

[0091] For purposes of this invention, a 180° rotation is interpreted as covering substantially 180° and is entirely dependent on the contours of the interface portions of the first and second track elements, with tolerances to allow the first and second track elements to connect to one another to form a single elongated track element extending in either the first or second direction. A track surface is defined as the surface on which the wheels of a load handling device roll. The dual track includes guide surfaces 69a, 69b, and 69c to constrain the wheels of the load handling device on their respective track surfaces. In a specific embodiment of the invention, the guide surfaces of the dual track include opposing lips or ridges 69a, 69b (one lip on one side of the track and another lip on the other side) that run along each longitudinal edge of the track to guide or limit lateral movement of each wheel on the track, and a central lip or ridge 69c that runs parallel to the lips along the edge of the track. The central lip or ridge 69c is the same distance from each of the track edge lips or ridges 69a, 69b, so that the area between the central lip 69c and the track edge lips 69a, 69b provides two track surfaces 110a, 110b for allowing wheels of adjacent load handling devices to pass each other in both directions on the same track.

[0092] In a specific embodiment of the invention, the interface portions 210a, 210b of each of the first and second track elements 206, 208 include three steps 212a, 212b, 212c that connect together when the first and second track elements 206, 208 are brought together, so that the guide surfaces 69a, 69b on the outer edges of each track element and the central guide surface 69c abut in a continuous manner along the first and second track elements 206, 208, as shown in FIG. 47(a). The wheel assemblies of the load handling device, comprising pairs of wheels at the front and rear of the load handling device, can roll on the track surfaces across the first and second track elements 206, 208. Movement of the track elements as a result of thermal expansion and contraction, caused by the sliding connection between the first and second track elements, is shown in FIGS. 47(b and c). When the first and second orbital elements separate, gaps 214a, 214b, and 216 are created in the orbital surfaces between the first and second orbital elements 206 and 208. The geometry of the interface between the first and second orbital elements is such that the two gaps 214a, 214b—the first gap 214a in the first orbital surface 110a and the second gap 214b in the second orbital surface 110b—are offset from each other along the length of at least a portion of the orbit, with the first gap 214a being offset from the second gap 214b along the length of the orbit. In addition to the first and second gaps 214a, 214b in the first and second orbital surfaces 110a, 110b, the central ridge 69c also separates to create the central or third gap 216. The sizes of the first gap 214a, the second gap 214b, and the third gap 216 change as the first and second track elements 206, 208 separate, as demonstrated in Figures 47(b) and 47(c). The interface portions 210a, 210b of the first and second track elements 206, 208 are such that there is no continuous gap extending laterally across the track when the first and second track elements are pulled apart. This is to prevent the wheels of the load handling device from dropping or falling into the gap when the first and second track elements separate.

[0093] The offset of the first and second gaps 214a, 214b is such that when the first and second track elements separate, a continuous track surface still exists for the wheels of the load handling device to travel across the expansion joint. In other words, the interface portions 210a, 210b of the first and second track elements 206, 208 still overlap in a direction perpendicular to their longitudinal directions when the first and second track elements separate. This has the advantage that when the first and second track elements separate, the wheels of the load handling device can still travel on their respective track surfaces. This is demonstrated in Figures 48 and 49, which show parallel sets of track in the form of single elongated track elements, each track of the parallel set of track equipped with an expansion joint of the present invention to allow pairs of wheels at the front and rear of the load handling device to travel on the track. Figure 49 demonstrates that the offset of the gaps when the first and second track elements separate results in the wheels being restrained on the track surface by the guide surfaces. As the wheel 36 moves on the track surface of the first track element 206, the wheel 36 is restrained by the guide surface 69 a at the edge of the first track element 206. Additionally, when the first and second track elements separate, the width of the track surface in the interface area where they meet is reduced—that is, reduced by half so that only half the width of the wheel is supported on the reduced portion of the track surface. As the wheel reaches the end of the track surface of the first track element 206 and approaches the gap 214 a in the track surface, the wheel's restraint on the track surface changes from restraint by the guide surface 69 a at the edge of the track element to restraint by the central guide surface 69 c, as shown in FIG. 49 . Similarly, the wheel restrained by the central guide surface 69 c transitions to being restrained by one of the outer guide surfaces 69 a, b when the first and second track elements separate.

[0094] In this way, the wheels are always constrained on the track surface as they travel across the first and second track elements 206, 208, even when the first and second track elements separate. Again, the width of the track surface reduces as the wheels of the load handling device travel over the track surface of the second track element so that only half the width of the wheels is supported by the track surface as they travel across the gap 214a. The wheels of the load handling device are supported by the full width of the track surface after crossing the gap in the junction region between the first and second track elements.

[0095] A similar arrangement for restraining the wheels of a load handling device to their respective track surfaces when the first and second track elements separate is also demonstrated in Figures 24-27, where the first track element includes a protruding male portion that is receivable within a receiving female portion of the second track element. This is not true for the track element embodiment shown in Figure 23, in which the bridging member includes separate bridging elements that provide two track surfaces 110a, 110b. When the first and second track elements separate, the bridging member 110 provides little restraint for the wheels on their respective track surfaces, increasing the risk that the wheels may derail from the track surfaces when the first and second track elements separate.

[0096] However, in contrast to the arrangement of the first and second track elements in the embodiment shown in Figures 24-27, the gaps 214a, 214b in the track surfaces are longitudinally offset from one another so that when the first and second expansion joints are arranged parallel, the gap in the first expansion joint 218a is always directly opposite the complete track surface in the second expansion joint 218b, which is parallel to the first expansion joint 218a. A wheel of a load handling device traveling across the parallel first and second expansion joints 218a, 218b experiences only one gap at any one time, rather than multiple gaps multiple times as in the embodiment shown in Figures 23 and 26. This reduces the amount of wheel jamming or collision with the gap and further reduces the magnitude of the clunking noise of the load handling device on the track. Contrast this configuration with the expansion joint configurations shown in Figures 23 and 26, in which the front wheels simultaneously experience two gaps in the first and second expansion joints, and the rear wheels simultaneously experience two gaps, resulting in increased levels of jamming or collision of the load handling device wheels and further increasing the clunking phenomenon of the load handling device on the track. The only opportunity for the front and rear wheels to simultaneously experience multiple gaps in the embodiment shown in Figures 48(a and b) is the gap 216 created in the centers of the track surfaces of the first and second track elements when their respective central guide surfaces 69c separate. The most significant advantage of the embodiment shown in Figure 46 is the ability to use a single type of track element for the first and second track elements, thereby reducing the number of different parts required to assemble the grid structure.

[0097] To allow the first track element to pivot relative to the second track element, both track elements are supported on a sliding connection. There are numerous examples of sliding connections according to the present invention. In a first example, shown in FIG. 50, the sliding connection 220 is similar to the track support element 56 discussed above with reference to FIG. 10, but includes back-to-back C-sections 222, 224 that are arranged to slide relative to each other within the overlapping joint area of ​​the track elements. The sliding connection within the overlapping joint area of ​​the track elements is provided by a slot 226 and sliding bearing 228 arrangement, in which one end of the C-section includes a slot that cooperates with the sliding bearing that connects the C-sections together. In another example, shown in FIG. 51, the sliding section supporting the first and second track elements 206, 208 includes a plate or bar 230. Both the first and second track elements 206, 208 have openings or recesses 232 for receiving the ends of the plate 230 in the sliding connection. In the particular embodiment shown in FIG. 51, the first and second tracks 206, 208 are box sections for receiving ends of plates 230. One end of the plate is secured to the second track element as shown in FIG. 51 using a suitable fastener 234, e.g., a bolt, screw, or pin, and the second end of the plate is receivable within a recess or opening 232 in the first track element 206. When received within its respective recesses in the first and second track elements, the plate's surface supports the upper track contours of the first and second track elements from buckling under the weight of a load handling device traveling on the track elements.

[0098] As with the other embodiments discussed above, the expansion joints in the embodiments discussed with reference to Figures 46-51 can form part of a bridging joint assembly for connecting different regions of a grid structure as discussed above. A cap plate 158 for interconnecting adjacent uprights with track support elements supporting first and second track elements is shown in Figure 50. Here, the ends of the track support elements are connected to their respective cap plates, which are used to fasten to the uprights. In addition, mechanical fuses can be used to connect the track supports to the uprights through the cap plates. When the track support elements are back-to-back C-sections as shown in Figure 50, mechanical fuses can be incorporated into sliding bearings in the joint area where the back-to-back C-sections overlap. Alternatively, mechanical fuses can be incorporated into the fasteners used to connect one of the track support elements to its respective cap plate.

[0099] Various modifications of the exemplary embodiments that are apparent to those skilled in the art within the scope of the invention as defined in the claims are deemed to be within the scope of the invention, for example, a combination of mechanical fuses may be used to interconnect at least one of the plurality of upright members to the grid member via a cap plate, along with a mechanical fuse used to connect the ends of adjacent grid members via a bridging joint assembly. The inventions described in the original claims of this application are set forth below. [1] A grid framework structure for supporting a load handling device operable to move one or more containers, said grid framework structure comprising: a plurality of upright members arranged to form a plurality of vertical locations for one or more containers to be guided vertically by the upright members; wherein the plurality of upright members are interconnected by a plurality of grid members arranged in a grid pattern to define nodes at their upper ends, the grid members comprising a first set of grid members extending in a first direction and a second set of grid members extending in a second direction, the second set of grid members passing transversely to the first set of grid members in a substantially horizontal plane to form a grid structure comprising a plurality of grid cells; the grid structure comprising a track system positioned on the plurality of grid members, the track system comprising a plurality of tracks arranged in the grid pattern; the grid structure comprises a first region and a second region; wherein the grid framework structure further comprises a bridging joint assembly disposed as one or more connections between the first region of the grid structure and the second region of the grid structure, the bridging joint assembly comprising at least one mechanical fuse disposed to break under an applied load equal to or greater than a predetermined load, the predetermined load being less than a load for breaking the interconnections between the plurality of upright members and the plurality of grid members of the grid structure to allow the first region of the grid structure to separate from the second region of the grid structure when the applied load exceeds the predetermined load. [2] The grid framework structure of [1], wherein the at least one mechanical fuse comprises at least one shear pin configured to break when the applied load in a direction parallel to the first direction or the second direction exceeds the predetermined load. [3] The grid framework structure of [1] or [2], wherein the bridging joint assemblies are configured to connect ends of adjacent grid members within the grid structure. [4] The grid framework structure of [3], wherein the bridging joint assembly comprises at least one bracket arranged to connect the ends of adjacent grid members by a plurality of fasteners, at least one of the plurality of fasteners comprising at least one mechanical fuse arranged such that the bracket separates from at least one end of the adjacent grid member when the applied load on the at least one mechanical fuse exceeds the predetermined load. [5] The grid framework structure according to [4], wherein the bridging joint assembly comprises at least one sliding bearing arranged to cooperate with a slot in the bracket and / or in the at least one end of the adjacent grid member within a joint area where the at least one bracket is arranged to overlap the at least one end of the adjacent grid member to allow the at least one bracket and the at least one end of the adjacent grid member to slide relative to each other. [6] The grid framework structure according to [4] or [5], wherein the at least one bracket comprises first and second brackets disposed on opposite sides of the at least one end of the adjacent grid member. [7] A grid framework structure as described in any one of [1] to [6], wherein the bridging joint assembly is positioned to connect at least one of the plurality of upright members to at least one of the plurality of grid members. [8] The grid framework structure of [7], wherein the bridging joint assembly comprises a cap plate, the cap plate being cross-shaped with four connection portions for connecting to separate grid members within the grid structure, and at least one of the four connection portions being connected to a grid member by the at least one mechanical fuse. [9] The grid framework structure of any one of [1] to [8], wherein the bridging joint assembly further comprises an expansion joint comprising a first track element and a second track element, and the bridging member extends across the ends of the first and second track elements to provide a continuous track surface extending longitudinally in the first or second direction across the ends of the first and second track elements.

[10] The grid framework structure of [9], wherein the bridging member has a first end attached to the first track element and a second end movable relative to the second track element.

[11] The grid framework structure of

[10] , wherein the second end of the bridging member is configured to be received within a correspondingly shaped recess in the second track element.

[12] The grid framework structure according to

[10] or

[11] , wherein the second end of the bridging member is positioned to overlap the second track element.

[13] The grid framework structure of any one of [9] to

[12] , wherein the bridging member further comprises a guide member constrained to slide along a groove in the second track element.

[14] The grid framework structure of any one of [9] to

[13] , wherein the bridging joint assembly further comprises a support arranged to support the bridging member within a joint area between the ends of the first and second track elements.

[15] The grid framework structure of any one of [1] to

[14] , wherein the first region of the grid structure is located on a mezzanine level.

[16] The grid framework structure of any one of [1] to

[15] , wherein the first region of the grid structure comprises one or more ports through which storage containers can be transferred out of and / or into the grid framework structure.

[17] The grid framework structure of any one of [1] to

[16] , wherein at least a portion of the plurality of upright members are arranged to form a plurality of vertical storage columns for stacking one or more storage containers between the at least a portion of the plurality of upright members.

[18] The grid framework structure according to

[17] , wherein the second region of the grid structure is positioned above at least some of the upright members forming the vertical storage columns.

[19] The grid framework structure of

[17] or

[18] , wherein the plurality of upright members comprises first and second sets of upright members, and wherein at least a portion of the plurality of upright members defines the second set of upright members such that the first region of the grid structure is disposed above the first set of upright members.

[20] The grid framework structure according to

[19] , wherein the first set of upright members have a different length than the second set of upright members.

[21] The grid framework structure of any one of [1] to

[20] , wherein the plurality of grid members comprises a plurality of first type grid members arranged in the grid pattern to define the first area of ​​the grid structure, and a plurality of second type grid members arranged in the grid pattern to define the second area of ​​the grid structure, and the first type grid members are different from the second type grid members.

[22] The grid framework structure according to

[21] , wherein each grid member of the plurality of second-type grid members has a bending strength greater than each grid member of the plurality of first-type grid members.

[23] A storage and retrieval system comprising: i) a grid framework structure according to any one of [1] to

[22] ; ii) a plurality of stacks of containers disposed in storage columns positioned below a grid, wherein each storage column is positioned vertically below a grid cell; iii) a plurality of load handling devices for lifting and moving containers stacked in the stack, the plurality of load handling devices being remotely operated to move laterally on the grid above the storage columns to access the containers through the grid cells, each of the plurality of load handling devices: a) a wheel assembly for guiding the load handling device over the grid; b) a container receiving space located above said grid; c) a lifting device arranged to lift a single container from the stack into said container receiving space; A storage and retrieval system comprising:

Claims

1. 1. A grid framework structure for supporting a load handling device operable to move one or more containers, said grid framework structure comprising: a plurality of upright members arranged to form a plurality of vertical locations for one or more containers to be guided vertically by the upright members; wherein the plurality of upright members are interconnected by a plurality of grid members arranged in a grid pattern to define nodes at their upper ends, the grid members comprising a first set of grid members extending in a first direction and a second set of grid members extending in a second direction, the second set of grid members passing transversely to the first set of grid members in a substantially horizontal plane to form a grid structure comprising a plurality of grid cells; the grid structure comprising a track system positioned on the plurality of grid members, the track system comprising a plurality of tracks arranged in the grid pattern; the grid structure comprises a first region and a second region; wherein the grid framework structure further comprises a bridging joint assembly disposed as one or more connections between the first region of the grid structure and the second region of the grid structure, the bridging joint assembly comprising at least one mechanical fuse disposed to break under an applied load equal to or greater than a predetermined load, the predetermined load being less than a load for breaking the interconnections between the plurality of upright members and the plurality of grid members of the grid structure to allow the first region of the grid structure to separate from the second region of the grid structure when the applied load exceeds the predetermined load; a grid framework structure, wherein the bridging joint assembly further comprises an expansion joint comprising a first track element and a second track element, the bridging member extending across the first and second track elements to provide a continuous track surface extending longitudinally in the first or second direction across the ends of the first and second track elements.

2. 2. The grid framework structure of claim 1, wherein the at least one mechanical fuse comprises at least one shear pin configured to break when the applied load in a direction parallel to the first direction or the second direction exceeds the predetermined load.

3. The grid framework structure of claim 1 , wherein the bridging joint assemblies are configured to connect ends of adjacent grid members within the grid structure.

4. 4. The grid framework structure of claim 3, wherein the bridging joint assembly comprises at least one bracket arranged to connect the ends of adjacent grid members by a plurality of fasteners, at least one of the plurality of fasteners comprising at least one mechanical fuse arranged such that the bracket separates from the at least one end of the adjacent grid member when the applied load on the at least one mechanical fuse exceeds the predetermined load.

5. 5. The grid framework structure according to claim 4, wherein the bridging joint assembly comprises at least one sliding bearing arranged to cooperate with a slot in the bracket and / or in the at least one end of the adjacent grid member within a joint area where the at least one bracket is arranged to overlap the at least one end of the adjacent grid member to allow the at least one bracket and the at least one end of the adjacent grid member to slide relative to each other.

6. The grid framework structure of claim 4 , wherein the at least one bracket comprises first and second brackets disposed on opposite sides of the at least one end of the adjacent grid members.

7. The grid framework structure of claim 1 , wherein the bridging joint assembly is positioned to connect at least one of the plurality of upright members to at least one of the plurality of grid members.

8. 2. The grid framework structure of claim 1, wherein the bridging member has a first end attached to the first track element and a second end movable relative to the second track element.

9. The grid framework structure of claim 8 , wherein the second ends of the bridging members are configured to be received within correspondingly shaped recesses in the second track elements.

10. A grid framework structure as described in claim 9, wherein the bridging member is integrally formed with the first track element as a protruding male portion, and the second track element has a receiving female portion.

11. The grid framework structure of claim 1 , wherein the bridging members further comprise guide members constrained to slide along grooves in the second track elements.

12. 2. The grid framework structure of claim 1, wherein the bridging joint assembly further comprises a support positioned to support the bridging member within a joint area between the ends of the first and second track elements.

13. The grid framework structure of claim 1 , wherein the first region of the grid structure is located on a mezzanine level.

14. 2. The grid framework structure of claim 1, wherein at least a portion of the plurality of upright members are arranged to form a plurality of vertical storage columns for one or more storage containers to be stacked between the at least a portion of the plurality of upright members.

15. 15. The grid framework structure of claim 14, wherein the second region of the grid structure is disposed above the at least some of the plurality of upright members forming the plurality of vertical storage columns.

16. 15. The grid framework structure of claim 14, wherein the plurality of upright members comprises first and second sets of upright members, and wherein the at least some of the plurality of upright members define the second set of upright members such that the first region of the grid structure is disposed above the first set of upright members.

17. 17. The grid framework structure of claim 16, wherein the first set of upright members have a different length than the second set of upright members.

18. 2. The grid framework structure of claim 1, wherein the plurality of grid members comprises a plurality of first type grid members arranged in the grid pattern to define the first area of ​​the grid structure and a plurality of second type grid members arranged in the grid pattern to define the second area of ​​the grid structure, the first type grid members being different from the second type grid members.

19. 20. The grid framework structure of claim 18, wherein each grid member of said plurality of second-type grid members has a greater bending strength than each grid member of said plurality of first-type grid members.

20. 1. A storage and retrieval system comprising: i) a grid framework structure according to any one of claims 1 to 19; ii) a plurality of stacks of containers disposed in storage columns positioned below a grid, wherein each storage column is positioned vertically below a grid cell; iii) a plurality of load handling devices for lifting and moving containers stacked in the stack, the plurality of load handling devices being remotely operated to move laterally on the grid above the storage columns to access the containers through the grid cells, each of the plurality of load handling devices comprising: a) a wheel assembly for guiding said load handling device over said grid; b) a container receiving space located above said grid; c) a lifting device arranged to lift a single container from the stack into said container receiving space; A storage and retrieval system comprising:

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