Rail system for a storage and retrieval system

Abstract

A track system (13) for a storage and retrieval system, the track system (13) comprising a first set of tracks extending along a first direction X and a second set of tracks extending along a second direction Y substantially perpendicular to the first direction X, each set of the first and second sets of tracks comprising a plurality of track elements, characterized in that at least a section of at least one track element (50) of the first and / or second sets of tracks comprises a plurality of staggered slots, such that the at least one track element (50) is compliant.

Description

Technical Field

[0001] This invention relates to a track system for an automated storage and retrieval system. Background Technology

[0002] The invention for which protection is sought aims to provide improvements in automated storage and retrieval systems.

[0003] Thermal expansion and contraction become problematic in rigid structures, especially large rigid structures. Although the expansion of each individual component in the structure is small, the cumulative displacement can be very significant when the overall structure is large. Without considering thermal expansion and contraction, the relative motion within the structure can lead to bending and fracture of the components.

[0004] Thermal expansion becomes a problem in automated storage and retrieval systems with large, rigid grid frame structures. The grid frame structure comprises a track system supported by a supporting frame structure. Stacks of storage containers are housed within the supporting frame structure beneath the track system. In large grid frame structures, the track system is particularly susceptible to thermal expansion and contraction.

[0005] A track system is formed by several track elements or sections, which are cut at right angles and joined together. Sometimes, gaps are left between the ends of adjacent tracks to allow for thermal expansion of the track elements or sections. The cuts of the track sections result in gaps that intersect the tracks perpendicularly. The joints at the intersections of track elements create small steps for vehicles or load handling devices traveling on the tracks and approaching. As a vehicle approaches the track joint, its wheels may get stuck or hit the edge of the track as it crosses the intersection. The vertical displacement of the wheels is exacerbated by the gaps between the intersecting tracks or track groups as the vehicle travels through the intersection. In this case, as the vehicle approaches the track joint, the wheels may get stuck in the gap. Due to the narrowness of the gap, the wheels may hit the edge of the next track section as they sink in. After rolling through the gap, the wheels will rise to the surface of the next track section.

[0006] Another solution to the problem of thermal expansion and contraction of track systems on grid frame structures is to use expansion joints. This method does not require gaps between the ends of adjacent tracks to allow for thermal expansion. Figure 6An expansion joint is illustrated. The expansion joint 2 includes a sliding plate 4 covering the track and positioned at the junction between two track sections 6 and 8. The sliding plate 4 is fixed to the first track section 6 and rests on and slides against the second track section 8 (not shown). As the sliding plate 4 moves relative to and slides past the second track section 8, the two track sections 6 and 8 can thus move relative to each other. The sliding plate 4 compensates for the thermal expansion, contraction, and movement of the mesh. However, this solution has several problems: the expansion joint cannot be resized for mesh frame structures of different sizes; the sliding movement of the sliding plate on the second track section can cause wear; the raised profile of the sliding track can exert impact loads on load handling devices passing over it and may lead to inaccuracies in position and / or velocity measurements.

[0007] In addition to thermal expansion and contraction, the orbital system also needs to consider other movements that occur in the grid frame structure due to seismic activity, such as the movement of the lower track supports. Summary of the Invention

[0008] The present invention is a track system for a storage and retrieval system, the track system comprising a first set of tracks extending along a first direction and a second set of tracks extending along a second direction substantially perpendicular to the first direction, each set of the first and second sets of tracks comprising a plurality of track elements, characterized in that at least a section of at least one track element of the first and / or second sets of tracks comprises a plurality of staggered slots so that at least one track element has compliance.

[0009] Adaptive track elements allow for thermal expansion, contraction, and other movements within the track system and the underlying grid frame structure, such as movements caused by seismic activity. A key advantage of using compliant track elements instead of traditional expansion joints is the absence of sliding parts. The relative movement of sliding parts due to structural thermal expansion or contraction leads to wear. For example, in the aforementioned prior art expansion joints, the sliding plate and the second track section slide against each other, causing wear on both. The absence of sliding parts means less wear on compliant track elements and potentially a longer operational life.

[0010] Another major benefit of using compliant track elements is the smooth profile. In contrast, in existing expansion joints, the presence of a sliding plate means that the path of the load handling device moving above the joint is neither smooth nor continuous. As the load handling device passes the sliding plate, the wheels collide when climbing onto it and again when leaving it. Although the vertical displacement of the wheels is very small as the vehicle travels over the flange of the sliding plate, this up-and-down impact on the wheels generates noise and vibration in the load handling device. Crossing the expansion joint applies impact loads to the load handling device, and this repeated application subsequently causes wear or damage to both the wheels and the track. The impacts on the wheels are transmitted to the main body of the load handling device, and in the worst case, can reduce the expected lifespan of its internal components. Using compliant track elements eliminates these impact loads and provides a smoother ride for the load handling device, significantly mitigating the effects of wear.

[0011] For load handling devices and / or control systems, knowing the location of each load handling device on top of the grid frame structure is crucial. This location information allows the load handling device to travel to a specific track and retrieve a specific container, avoiding collisions with other load handling devices and / or movement beyond the boundaries of the grid frame structure. Therefore, as described in UK patent application GB2020681.9, the load handling device includes a device for detecting its position and / or velocity on the grid. This functionality can be achieved by a wheel encoder for measuring the velocity of one or more wheels in the load handling device. In some applications, the wheel encoder can be coupled to additional position wheels. Rolling over the sliding plate of a prior art expansion joint can cause the position wheels to slip or lose traction, thus affecting the accuracy of the wheel encoder's velocity or position measurements. However, with compliant track elements, the profile at the top of the track is relatively smooth, and the wheels of the load handling device can maintain traction and not slip.

[0012] The conformal track of this invention further has the advantage of replacing one or more expansion joints with simpler parts. Reducing the number of parts and complexity lowers manufacturing and installation costs.

[0013] The width of the interlaced slots will change as at least one track element deforms.

[0014] A plurality of interlaced slots extend in a direction substantially perpendicular to the longitudinal direction of at least one track element.

[0015] At least one track element has several slots that are uniformly spaced along at least a segment of the track element. The advantage of uniform spacing is that deformation and applied force can be distributed along the segment of the track element containing the slots. Alternatively, the spacing between the slots can be varied to accommodate the deformation of the at least one track element.

[0016] In a first embodiment of the invention, the staggered slots may include a first set of slots and a second set of slots, which are staggered. Each slot in the first and second sets of slots has an open end and a closed end, wherein the open ends of the first and second sets of slots are located on opposite sides of the track element. An advantage of this first embodiment is that the material between the slots forms a long deformation path between the staggered slots. The deformation can be distributed along the deformation path, thus achieving a large cumulative deformation of the track element only requires a small deformation in each segment of the deformation path.

[0017] In a second embodiment of the invention, the staggered slots may include a first group of slots, a second group of slots, and a third group of slots. Each slot in the first and second groups of slots has an open end and a closed end, wherein the open ends of the first and second groups of slots are located on opposite sides of at least one track element, and wherein the third group of slots is a closed-end slot with a closed end, such that the third group of slots is staggered with the first and second groups of slots. The first and second groups of slots may include several pairs of open-end slots, such that the open ends of the several pairs of open-end slots face each other on opposite sides of the track segment.

[0018] The advantage of the second specific embodiment is that the arrangement of the slots is symmetrical about the longitudinal axis of the track element, so that the deformation is kept in the center and the track element is less sensitive to unintended deformation (e.g., bending) in other directions.

[0019] The closed ends of staggered slots can have a circular cross-section. The advantage of a circular cross-section is that there are no sharp corners that act as stress concentrators. If the ends of the slots are not rounded (for example, if the ends have a square cross-section), stress will concentrate at the sharp corners, and the track element will not deform that far before reaching its elastic limit.

[0020] The closed end of the staggered slot can have a keyhole profile. Like the circular profile, the advantage of the keyhole profile is that it does not have sharp corners that act as stress concentration points.

[0021] The track system may include a first segment and a second segment, each segment including a first set of tracks extending along a first direction and a second set of tracks extending along a second direction substantially perpendicular to the first direction, wherein the first and second segments of the track system are joined by a link including at least one track element, the at least one track element including staggered slots such that the link between the first and second segments of the track system is compliant.

[0022] Because different fulfillment centers have different sizes of grid frame structures, the total cumulative displacement of the track system due to thermal expansion or contraction will also vary from fulfillment center to fulfillment center. The size range of fulfillment centers is very wide, from micro or mini fulfillment centers serving urban areas as convenience stores to very large fulfillment centers—such as Ocado's approximately 600,000 square foot customer fulfillment center in Erith.

[0023] Modular grid frame structures feature a track system divided into several sections, with compliant track elements located between these sections. The advantage of this modular grid frame structure is that expansion and contraction can vary depending on the size of the grid frame structure. The same compliant track elements can be used in grid frame structures of different sizes with different performance centers. Traditional expansion joints require redesign for each performance center to account for different cumulative displacements, thus incurring additional development time and costs.

[0024] To create a track system that can be completely resized to accommodate grid frame structures of any size, the track system can be divided into several standard-sized segments, with different numbers of segments used for different sized grid frame structures. For example, if the track system segments have a standard size of 50×50 grid cells, then four segments can be used for a grid frame structure with a size of 101×101 grid cells; in each direction, one segment will have 50 grid cells, with compliant links between the segments forming a central grid cell, followed by another segment with 50 grid cells. Other sizes can be formed using different numbers of segments in the track system, such as 152×152 grid cells formed by 9 segments, 203×203 grid cells formed by 16 segments, or any other desired size. Therefore, the same design of track system segments and compliant links can be used for various sizes of grid frame structures, and thus also for various sizes of fulfillment centers.

[0025] At least one track element may include two or more track elements.

[0026] At least one track element may be formed by casting, machining, or extrusion. Interlaced slots may be machined into at least one track element. At least one track element may be made of metal or plastic. Any other suitable material may also be used. The advantage of achieving the desired compliance through slot arrangement rather than material selection is that the compliant track element can be made of the same material as the standard track element. The benefit of this is that the compliant track element can use the same material and the same basic design as the standard rigid track element; the only difference is that the compliant subset of the track element has interlaced slots machined into it.

[0027] At least one track element may be supported by track supports connected together by at least one connecting member, the at least one connecting member being configured to slide relative to at least one track support in use, so that the track supports can move relative to each other in the longitudinal direction.

[0028] The present invention also covers a grid frame structure for a storage and retrieval system, the grid frame structure comprising, as described above, a support frame structure supporting the track system, and a plurality of container stacks arranged in storage columns located below the track system.

[0029] The present invention also covers a storage and retrieval system comprising a grid frame structure as described above and one or more load handling devices for lifting and moving containers stacked in a stack, each load handling device including a wheel assembly for moving the load handling device on a track system, a container receiving space located above the track system, and a lifting device arranged to lift individual containers from the stack to the container receiving space. Attached Figure Description

[0030] The present invention will now be described in detail with reference to the embodiments, wherein:

[0031] Figure 1 The grid frame structure and container are schematically illustrated.

[0032] Figure 2 Schematic illustration of the location Figure 1 The track at the top of the grid frame structure shown;

[0033] Figure 3 Schematic illustration of the location Figure 1 The load handling device at the top of the grid frame structure shown;

[0034] Figure 4 A single load handling unit is schematically shown, which has a container lifting device in a lowered configuration;

[0035] Figure 5A schematic cross-sectional view of a single load handling unit is shown, which has container lifting devices in raised and lowered configurations;

[0036] Figure 6 The diagram illustrates an expansion joint in the prior art.

[0037] Figure 7 A compliant track element according to a first embodiment of the present invention is schematically shown;

[0038] Figure 8 yes Figure 7 Top view of the compliant track section;

[0039] Figure 9 A compliant track element according to a second embodiment of the present invention is schematically shown;

[0040] Figure 10 yes Figure 9 Top view of the compliant track element;

[0041] Figure 11 The deformation paths of the compliant track element for (a) a first embodiment and (b) a second embodiment of the present invention are shown;

[0042] Figure 12 The compliant track element according to a first specific embodiment of the present invention is shown in (a) a stretched state and (b) a compressed state;

[0043] Figure 13 The compliant track element according to a second specific embodiment of the present invention is shown in (a) a stretched state and (b) a compressed state;

[0044] Figure 14 The closed end of the slot with (a) a square section, (b) a circular section and (c) a keyhole section is shown;

[0045] Figure 15 An interlaced slot in a track element of a first embodiment is shown, having (a) a wider gap and (b) a narrower gap located between the closed end of the slot and the side of the track element;

[0046] Figure 16 The second embodiment shows an interlaced slot in a track element having (a) a wider gap and (b) a narrower gap located between the closed end of the slot and the side of the track element;

[0047] Figure 17 The diagram shows a track system comprising four sections connected by compliant links;

[0048] Figure 18The compliant track element supported by several track supports is shown in (a) isometric view and (b) side view. Detailed Implementation

[0049] The following detailed descriptions represent preferred embodiments of how the applicant implements compliant track elements, but they are not necessarily the only embodiments for achieving this purpose.

[0050] Storage and retrieval system

[0051] Figure 1 A grid frame structure 1 for a storage and retrieval system is shown. The grid frame structure includes a track system 13, which includes a first set of tracks 17 extending along a first direction and a second set of tracks 19 extending along a second direction. The tracks 17 and 19 of the track system 13 are arranged in a grid pattern comprising a plurality of grid cells. The track system 13 is supported on top of a supporting frame structure. The supporting frame structure creates a storage space comprising a plurality of storage columns 10 below the track system 13. Each storage column 10 is arranged to store a stack of storage containers.

[0052] exist Figure 1 In the specific embodiment shown, the grid frame structure 1 includes upright members 3 and horizontal members 5 and 7 supported by the upright members 3. The horizontal members 5 are parallel to each other and extend parallel to the x-axis shown. The horizontal members 7 are parallel to each other and extend parallel to the y-axis shown, and extend laterally to the horizontal members 5. The upright members 3 are parallel to each other and extend parallel to the z-axis shown, and extend laterally to the horizontal members 5 and 7. The horizontal members 5 and 7 form a grid pattern defining a plurality of grid cells. In the illustrated embodiment, containers 9 are arranged in stacks 11 below the grid cells, each grid cell containing a stack 11 of containers 9, the grid cells being defined by the grid pattern.

[0053] like Figure 1 The supporting frame structure shown can be described as a "stick-built" design, comprising upright members 3 supporting the horizontal grid members 5 and 7. PCT patent (Ocado) publication number WO2015 / 185628A details a "stick-built" grid structure for a storage and fulfillment or distribution system, in which several container stacks are arranged within the grid frame structure; the contents of that patent are incorporated herein by reference. Several containers can be accessed via a load handling device that operates remotely on a track atop the grid frame structure.

[0054] The support frame structure is not limited to a "component-based" design and can also include other types of support grid frame structures. In other embodiments, the support frame structure may include a plurality of prefabricated modular panels arranged in a grid pattern. PCT application WO2022 / 034195A1 (Ocado) describes further details regarding prefabricated modular panels, which are incorporated herein by reference. The support frame structure includes a plurality of prefabricated modular panels arranged in a three-dimensional grid pattern to define a plurality of grid cells. By providing such a support frame structure, the grid frame structure addresses the time and cost issues required for assembly. The size of each grid cell in the support frame structure is designed to support two or more grid cells supporting the track system. The grid frame structure consists of fewer structural components but still maintains the same structural integrity as the aforementioned "component-based" grid frame structure, and is faster to construct and less expensive.

[0055] Figure 2 A large-scale plan view of a section of track structure 13 is shown, in which track structure 13 is formed. Figure 1 The portion of the grid frame structure 1 shown is located in... Figure 1 The top of the horizontal members 5 and 7 of the grid frame structure 1 shown. The track structure 13 may be provided by the horizontal members 5 and 7 themselves (e.g., formed in or on the surface of the horizontal members 5 and 7) or by one or more additional components mounted on top of the horizontal members 5 and 7. The track structure 13 shown includes an x-direction track 17 and a y-direction track 19, namely a first set of tracks 17 extending in the x-direction and a second set of tracks 19 extending in the y-direction and transverse to the first set of tracks 17. Tracks 17 and 19 define an aperture 15 at the center of the grid cell. The aperture 15 is designed to allow a container 9 located below the grid cell to be raised and lowered through the aperture 15. The x-direction tracks 17 are arranged in pairs separated by channels 21, and the y-direction tracks 19 are arranged in pairs separated by channels 23. Other arrangements of track structures are also possible.

[0056] Figure 3 It shows in Figure 1 A plurality of load handling devices 31 move at the top of the grid frame structure 1 shown. Each load handling device 31 (also referred to as an automated operating device 31 or robot 31) is equipped with wheels to engage with corresponding x or y direction tracks 17, 19, enabling the robot 31 to travel through the track structure 13 and reach specific grid cells. The paired tracks 17, 19 shown, separated by channels 21, 23, allow the robot 31 to occupy (or pass through) adjacent grid cells without colliding with each other.

[0057] like Figure 4As shown in detail, robot 31 includes a body 33, and one or more components that enable robot 31 to perform its intended functions are mounted in or on the body 33. These functions may include moving on track structure 13 through grid frame structure 1 and raising or lowering container 9 (e.g., from or to stack 11) so that robot 31 can retrieve or place container 9 at a specific location defined by the grid pattern.

[0058] The robot 31 shown includes a first set of wheels and a second set of wheels 35 and 37. The first and second sets of wheels 35 and 37 are mounted on the main body 33 of the robot 31, allowing the robot 31 to move along tracks 17 and 19 in the x and y directions, respectively. Specifically, the two wheels 35... Figure 4 The first wheel is visible on the shorter side of robot 31, while the other two wheels 35 are located on the opposite shorter side of robot 31 (this side and the other two wheels 35 are on...). Figure 4 (Not visible in the image). Wheel 35 engages with track 17 and is rotatably mounted on the body 33 of robot 31 to allow robot 31 to move along track 17. Similarly, two wheels 37... Figure 4 The first wheel is visible on the longer side of robot 31, while the other two wheels 37 are located on the opposite longer side of robot 31 (this side and the other two wheels 37 are on...). Figure 4 (Not visible in the image). Wheels 37 engage with track 19 and are rotatably mounted on the body 33 of robot 31 to allow robot 31 to move along track 19.

[0059] Robot 31 also includes a container lifting device 39 configured to raise and lower container 9. The container lifting device 39 includes four reels or spools 41 connected at their lower ends to a container engaging assembly 43. The container engaging assembly 43 includes engaging devices configured to engage features of container 9 (the engaging devices may be located, for example, at a corner of assembly 43, near the reels 41). For example, container 9 may have one or more holes on its upper side, and the engaging devices may engage with the holes. Alternatively or additionally, the engaging devices may be configured to hook onto an edge or flange below container 9, and / or clamp or grip container 9. The reels 41 may be wound upwards or downwards as needed to raise or lower the container engaging assembly. One or more motors or other devices may be provided to influence or control the upward or downward winding of the reels 41.

[0060] like Figure 5As seen, the main body 33 of the robot 31 has an upper portion 45 and a lower portion 47. The upper portion 45 is configured to accommodate one or more operating components (not shown). The lower portion 47 is arranged below the upper portion 45. The lower portion 47 includes a container receiving space or cavity for accommodating at least a portion of a container 9 that has been raised by the container lifting device 39. The container receiving space is designed to be large enough to place the container 9 inside the cavity so that the robot 31 can move across the track structure 13 on top of the grid frame structure 1 without the underside of the container 9 getting stuck on the track structure 13 or another part of the grid frame structure 1. When the robot 31 reaches its intended endpoint, the container lifting device 39 controls the reel 41 to lower the container gripping assembly 43 and the corresponding container 9 from the cavity of the lower portion 47 to the intended position. The intended position may be the stack 11 of the containers 9 or the exit of the grid frame structure 1 (or, if the robot 31 has moved to collect the containers 9 in the grid frame of the grid frame structure 1, the entrance of the grid frame structure 1). Although the upper and lower portions 45 and 47 are physically separated in the illustrated embodiment, in other embodiments, the upper and lower portions 45 and 47 may not be physically separated by specific components or parts of the main body 33 of the robot 31.

[0061] In some embodiments, the container receiving space of robot 31 may not be within the body 33 of robot 31. For example, in some embodiments, the container receiving space may be adjacent to the body 33 of robot 31, for example, using a cantilever arrangement, with the weight of the body 33 of robot 31 balancing the weight of the container to be lifted. In such embodiments, the frame or arm of container lifting device 39 may protrude horizontally from the body 33 of robot 31, and the tape / spool 41 may be arranged at various locations of the protruding frame / arm and configured to be raised and lowered at these locations to raise and lower the container into the container receiving space adjacent to the body 33. The height at which the frame / arm is mounted on the body 33 of robot 31 and the height at which it protrudes from the body 33 of robot 31 can be selected to achieve the desired effect. For example, for the frame / arm, it is preferable to protrude at a high level of the body 33 of robot 31 so that larger containers (or multiple containers) can be raised into the container receiving space below the frame / arm. Alternatively, the frame / arm may be positioned at a lower point on the main body 33 (but still high enough to accommodate at least one container between the frame / arm and the track structure 13) to maintain the center of gravity of the robot 31 when it is loaded with a container.

[0062] Figure 4 and Figure 5A specific embodiment of the load processing apparatus shown illustrates a load processing apparatus 31 with a body 33, wherein the body 33 is generally box-shaped, having four side walls and a top wall, and several components of the load processing apparatus 31 are housed within the body 33. In other embodiments, the body 33 may include an open frame or skeleton structure, and several components of the load processing apparatus 31 are supported in or on the open frame or skeleton structure.

[0063] To enable the robot 31 to move along the first and second directions on different wheels 35, 37, the robot 31 includes a wheel positioning mechanism for selectively engaging the first set of wheels 35 with the first set of tracks 17 or engaging the second set of wheels 37 with the second set of tracks 19. The wheel positioning mechanism is configured to raise and lower the first set of wheels 35 and / or the second set of wheels 37 relative to the body 33, thereby allowing the load handling device 31 to selectively move along the first or second direction through the tracks 17, 19 of the grid frame structure 1.

[0064] The wheel positioning mechanism may include one or more linear actuators, rotating components, or other devices for raising and lowering at least one set of wheels 35, 37 relative to the body 33 of robot 31 to bring the at least one set of wheels 35, 37 into contact with and out of contact with tracks 17, 19. In some embodiments, only one set of wheels is configured to be raised and lowered, and lowering one set of wheels effectively lifts other sets of wheels away from their corresponding tracks, while raising one set of wheels effectively lowers other sets of wheels to contact their corresponding tracks. In other embodiments, both sets of wheels may be raised and lowered, which advantageously means that the body 33 of robot 31 remains at substantially the same height, so the weight of the body 33 and the weight of the components mounted on the body do not need to be raised and lowered by the wheel positioning mechanism.

[0065] orbital system

[0066] The track system 13 is supported by a support frame structure. In embodiments where the support frame structure is a "component-type" support frame structure, the uprights of the grid frame structure are interconnected at the top of the uprights by intersecting tracks or rails within the grid frame structure. The tracks or rails may be supported by or incorporated into horizontal members 5, 7. In embodiments where the support frame structure comprises a plurality of prefabricated modular panels, each grid cell of the support frame structure is designed to support two or more grid cells of the track system.

[0067] In a grid structure, the intersections of tracks or rails are typically referred to as "nodes" of the grid structure. Generally, the first and second sets of tracks consist of individual elongated tracks or rail elements that connect to each other along the first and second directions at the points where they meet.

[0068] Tracks typically comprise elongated elements milled into profile to guide load handling devices on a track system. Typically, tracks are milled into profile to provide a single track surface so that a single load handling device can travel on the track, or to provide dual tracks so that two load handling devices can pass each other on the same track. In the case where the profile of the elongated element provides a single track, the track may include opposing flanges along the track length (one flange on one side of the track, the other flange on the other side) to guide or constrain lateral movement of each wheel on the track. In the case where the profile of the elongated element is a dual track, the track may include two pairs of flanges along the track length so that the wheels of adjacent load handling devices can pass each other on the same track in two directions. Alternatively, as disclosed in UK Patent Patent No. GB2016097.4 (Ocado), a dual track may comprise only two guide surfaces or flanges extending from the track surface, rather than two pairs of flanges.

[0069] This invention is applicable to both single and dual tracks, and can be applied to track elements of any shape or profile.

[0070] Adaptive Tracks – Detailed Implementation

[0071] The compliant track 50 of the invention, including staggered slots 52, will now be described with reference to the accompanying drawings. Although two illustrative embodiments are described herein, it will be understood that many different styles of staggered slots exist, and all of them are within the scope of the invention.

[0072] Figure 7 A compliant track element 60 according to a first specific embodiment of the present invention is shown. Figure 8 yes Figure 7 A top view of the track element. The compliant track 60 includes a plurality of slots 52. The slots lie in substantially parallel planes and are substantially perpendicular to the main longitudinal axis of the track, and therefore also substantially perpendicular to the direction of travel of the load handling device on the track. The slots 52 are evenly spaced within a section 51 of the compliant track element. The slots 52 are open-end slots, each slot 52 having an open end 54 or opening on the side of the track and a closed end 56 within the main body of the track section. The slots are staggered, that is, adjacent slots 52 have open ends 54 on opposite sides of the track. The main body of the track forms a zigzag deformable path 66 between the staggered slots 52.

[0073] The slot 52 can be divided into a first group of slots 62 and a second group of slots 64. The first group of slots 62 has an open end on the same side of the track. The second group of slots 64 has an open end on the track side opposite to the side where the open end of the first group of slots 62 is located. The slots are arranged in an alternating pattern such that each slot of the first group of slots 62 is directly located between two slots of the second group of slots 64, and each slot of the second group of slots 64 is directly located between two slots of the first group of slots 62, except for the first and last slots in the series that are adjacent only to another slot.

[0074] The track element is a compliant mechanism, and the arrangement of the slots allows the track element to be compliant even when the material used to manufacture the track is rigid rather than compliant. A compliant mechanism allows deformation within the elastic limit in a rigid material. Deformation paths 66 between the staggered slots... Figure 11 (As shown) provides a relatively long path through which structural forces can propagate and the track can deform. Therefore, the deformation of the track is uniformly distributed along the entire length of the segment 51 containing the interlaced slots of the track element, and allows for significant expansion / contraction while remaining within the material's elastic limit. Remaining within the material's elastic limit means that the deformation is completely reversible, and the track material does not undergo permanent deformation during the deformation process.

[0075] Figure 9 A second embodiment of the invention is shown, which is more resistant to bending than the first embodiment. Figure 10 yes Figure 9 A top view of the compliant track element. The compliant track 70 includes a plurality of slots 52. As in the first embodiment, the slots are also located in substantially parallel planes and are substantially perpendicular to the longitudinal axis of the track element 70, and therefore also substantially perpendicular to the direction of travel of the load handling device on the track. The slots 52 are evenly spaced within a section 51 of the compliant track element.

[0076] The slot 52 is divided into a first group of slots 72, a second group of slots 73, and a third group of slots 74. The first and second groups of slots 72 and 73 are open-end slots, having both open and closed ends. The open ends, or openings, are located on opposite sides of the track element 70 (the first group of slots 72 is located on the first side of the track element, and the second group of slots 73 is located on the opposite second side of the track element), while the closed ends are located within the main body of the track element. The third group of slots 74 is a closed-end slot, having two closed ends located within the main body of the track element 70. The first and second groups of slots 72 and 73 are arranged in pairs, with each pair of slots located in the same plane, and the open ends of each pair of slots located on opposite sides of the track element 70. The third group of slots 74 is arranged alternately with the first and second groups of slots 72 and 73, such that each slot in the third group of slots 74 is directly located between two pairs of slots in the first and second groups of slots 72 and 73, except for the first slot in the third group that is adjacent to only one pair of slots.

[0077] Figure 11 The deformation paths in the compliant track element are shown in (a) the first embodiment and (b) the second embodiment. Figure 11 In the first embodiment shown in (a), the deformable path 66 is depicted as interlacing between a first set of slots 62 and a second set of slots 64 in the staggered slots. Figure 11 In the second embodiment shown in (b), there are two deformation paths 76 located on opposite sides of the track element 70. The deformation paths are substantially symmetrical. The deformation path 76 on the left-hand side of the track element 70 interweaves between the first set of slots 72 and the third set of slots 74, while the deformation path 76 on the right-hand side of the track element 70 interweaves between the second set of slots 73 and the third set of slots 74. The two deformation paths 76 pass through both sides of the third set of slots 74.

[0078] The main advantage of the first embodiment is that open-end slots are easier to manufacture than closed-end slots, and a single deformation path provides a longer deformation path compared to embodiments with multiple deformation paths. A longer deformation path means deformation is distributed over a longer length, allowing for smaller deformations at each segment of the path while still meeting the cumulative deformation required for the entire path. The main advantage of the second embodiment is that the closed-end slots and the symmetrical arrangement of the slots make the design more stable. The track element of the second embodiment is more stable under torsion, resulting in more centralized / linear deformation and reducing the likelihood of unintended deformations such as bending and twisting.

[0079] The first and second embodiments of the present invention, or any other style of staggered slots, can be applied to single or dual tracks. Other embodiments of the present invention are also possible, featuring more than two deformation paths, such as three or four deformation paths. An even number of symmetrical deformation paths provides greater stability and resistance to deformation (e.g., bending or twisting) in directions other than the longitudinal direction of the track element. It is understood that many possible styles of staggered slots exist, and different styles of staggered slots can be adapted to different deformation requirements or different levels of thermal expansion / contraction. The first and second embodiments described above are merely examples, and any style of staggered slot is within the scope of the present invention.

[0080] Deformation

[0081] As ambient temperature increases, the track system undergoes thermal expansion. The compliant track elements (one or more) will need to contract to compensate for this expansion within the remaining portion of the track system. Therefore, the compliant track elements (one or more) will be in a state of compression. As the material on both sides of the slot is compressed more tightly along the longitudinal axis of the track element, the interlaced slots also narrow. The limiting factor for compression is when the slot is closed, as the width of the slot approaches zero.

[0082] Under compression, the open end slot becomes narrower at the open end compared to the closed end. The closed end slot becomes narrower towards the center of the slot compared to the closed end.

[0083] When the ambient temperature drops, the track system undergoes thermal contraction. One or more compliant track sections will need to expand to compensate for the contraction within the rest of the track system. Therefore, one or more compliant track elements will be in a stretched state. As the material on both sides of the slot is further stretched along the longitudinal axis of the track element, the staggered slots become wider.

[0084] Under tension, the open end slot becomes wider than the closed end slot at the open end. The closed end slot becomes wider towards the center of the slot compared to the closed end slot.

[0085] In both cases (tension and compression), deformation causes the width of the slot to vary along the length of the slot.

[0086] In addition to thermal expansion and contraction, compliant track elements (one or more) may also be under tension and / or compression due to other movements of the track system or the underlying grid frame structure, such as seismic activity.

[0087] Figure 12 and Figure 13 The deformation of a compliant track element under tension and compression is shown, with the direction of the applied force indicated by arrows. Figure 12 (a) A first embodiment 60 of the compliant track element in a stretched state is shown. As can be seen from the figure, the first and second sets of staggered slots 62, 64 have been deformed and widened, such that the open end 54 of the slot is wider than the closed end 56 of the slot. The length of the segment 51 in the compliant track occupied by the staggered slots 62, 64 increases along its longitudinal axis.

[0088] In contrast, when the first specific implementation 60 of the compliant track is as follows Figure 12 (b) In the compressed state, the first and second sets of interlaced slots 62, 64 have deformed and become narrower, making the open end 54 of the slot narrower than the closed end 56 of the slot. The length of the section 51 occupied by the interlaced slots 62, 64 in the compliant track decreases along its longitudinal axis.

[0089] Figure 13 (a) A second embodiment 70 of the compliant track element in a stretched state is shown. As can be seen from the figure, the first, second, and third groups of staggered slots 72, 73, and 74 have been deformed and widened. The open ends 54 of the first and second groups of slots 72 and 73 are wider than the closed ends 56 of the first and second groups of slots, while the center of the third group of slots 74 is wider than its ends. The length of the segment 51 in the compliant track occupied by the staggered slots 72, 73, and 74 increases along its longitudinal axis.

[0090] In contrast, when the second specific implementation 70 of the compliant track is as follows Figure 13 (b) As shown in the compressed state, the first, second, and third groups of interlaced slots 72, 73, and 74 have deformed and become narrower. The open ends 54 of the first and second groups of slots 72 and 73 are narrower than the closed ends 56 of the first and second groups of slots, while the center of the third group of slots 74 is narrower than its ends. The length of the segment 51 occupied by the interlaced slots 72, 73, and 74 in the compliant track decreases along its longitudinal axis.

[0091] Under compression, the width of the slot is a limiting factor because the slot has been compressed close enough. To ensure that track elements are not affected by compressive stresses exceeding those designed for track compressive stress, compression limiters can be used.

[0092] The arrangement of slots in a compliant track can be designed so that the track is more compliant in some directions than others. For example, a compliant track can be designed to expand more easily under tension and contract more easily under compression, but be less compliant with torsional or bending deformation.

[0093] staggered slot design

[0094] The shape of the closed end 56 of slot 52 is important because the end profile of the slot affects the stress characteristics of the compliant track element 50. The shape of the closed end of the slot can be selected to avoid high stress concentration factors, for example, by avoiding sharp corners and small features. Figure 14 The closed end of the slot with (a) a square section, (b) a circular section and (c) a keyhole section is shown.

[0095] The advantage of a rounded or keyhole-shaped profile at the end of a slot is that it avoids sharp corners that act as stress concentration points. Without any smoothing treatment on the end profile of the slot (e.g., ...), Figure 14 (a) The end has a square cross-section), and the sharp corner 82 concentrates stress, preventing the track element from deforming so far at the corner before the stress reaches fatigue stress or the elastic limit. Using Figure 14 In the circular cross-section of (b), the radius of curvature r at the end of the slot is equal to half the width w of the slot. Using... Figure 14 In the keyhole cross-section of (c), the slot can have a larger radius of curvature. To avoid sharp corners, a fillet radius of 84 can be applied to the slot end where the circular portion of the slot cross-section meets the straight portion of the slot cross-section. These slot end cross-sections are merely examples; various options are available for the slot end cross-sections, and slots of any shape are within the scope of this invention.

[0096] When determining the design of staggered slots, a trade-off must be struck between the number of slots and their width. Fewer, wider slots are easier to manufacture (fewer slots can be machined, and wider slots mean larger tolerances, allowing for the use of less precise tools). Additionally, wider slots with circular or keyhole profiles will have a larger radius of curvature and therefore a lower stress concentration factor. However, while a large number of narrower slots are more difficult to manufacture, deformation on each slot is reduced (potentially reducing deformation-induced stresses), and this provides smoother travel for the wheels of the load handling device traveling on the track.

[0097] The length of the slot is also an important design consideration. Longer slots allow for longer deformation paths and narrower gaps between the closed end of the slot and the side of the track element. Narrow gaps with minimal material resemble a hinge arrangement, and a track element with all slots long and all gaps narrow is like a series of hinges, where each gap acts as a single hinge.

[0098] The difference between the wide and narrow gaps is shown in Figure 15 and Figure 16 middle. Figure 15Interlaced slots in a track element with (a) a wider gap and (b) a narrower gap are shown. Gap 68 is located between the closed end of the interlaced slot and the side of the track element. A first set of slots 62 with an open end on the left-hand side of the track element has a gap 68 on the right-hand side of the track element, while a second set of slots 64 with an open end on the right-hand side of the track element has a gap 68 on the left-hand side of the track element. In the case of the narrower gap 68... Figure 15 In (b), the movable hinge at the narrower gap 68 is located Figure 11 The turning point of the deformation path 66 shown.

[0099] Figure 16 The diagram illustrates staggered slots in a track element with (a) a wider gap and (b) a narrower gap. In this embodiment, there are two sets of gaps: a first set of gaps 78 located between the closed ends of a pair of first and second sets of slots, and a second set of gaps 80 located between the closed end of a third set of slots and the side of the track element. For the first embodiment, in the case of narrower gaps 78 and 80… Figure 16 In (b), the movable hinges at the narrower gaps 78 and 80 are located Figure 11 The turning point of the deformation path 76 shown.

[0100] The length of the slot also affects manufacturing feasibility. In movable hinge arrangements with narrow gaps of 68, 78, and 80, tolerances are critical, and the machining of the slot must be precise, requiring more specialized tools than when machining wider gaps. Additionally, the track profile is also relevant; machining slots in the thinner or shallower sections of the track is easier than machining them in the thicker or deeper sections (e.g., the upward-extending flanges of the track). For example, from... Figure 7 and Figure 9 As can be seen, the slot terminates before the outer flange that extends upward at the edge of the track.

[0101] To avoid permanent deformation, compliant track elements must be designed to always remain within the elastic limit of the material used in the track. The maximum allowable stress can be calculated by multiplying a safety factor by the material's yield stress. Yield stress is the stress at which a material reaches its elastic limit; beyond this stress, the material may undergo permanent deformation.

[0102] Compliant track components can be designed to resist fatigue. The maximum allowable stress for fatigue can be calculated based on the track's expected service life (e.g., 20 years). Typically, fatigue stress is below the elastic limit; therefore, the design for fatigue will ensure that deformation always remains within the elastic limit. Fatigue stress can be determined, for example, by calculating the expected number N of expansion-contraction cycles (e.g., due to daily temperature cycles) during the track's expected service life and reading the stress from the material's SN curve. If different levels of stress or deformation are anticipated due to different types of loads (e.g., small deformations due to daily temperature cycles, annual seasonal temperature variations, and less frequent seismic activity), the miner's rule can be used to calculate the cumulative effect of different magnitudes of stress at different cycle numbers to determine the maximum allowable stress for the desired fatigue life. Once the maximum allowable stress is calculated, this stress value can be multiplied by a safety factor.

[0103] Those skilled in the art should understand that other methods exist for calculating fatigue life and maximum allowable stress (e.g., strain-life method, crack propagation method, and probabilistic method). The above embodiments are intended as non-limiting examples, and any suitable method may be used.

[0104] Based on the expected maximum and minimum temperatures, the target temperature range can be determined. Then, the maximum expected expansion / contraction of the mesh can be calculated using the target temperature range and the coefficient of thermal expansion of the material used in the orbital.

[0105] The change in the linear dimension of the orbit, ΔL, is:

[0106]

[0107] Where L is the nominal length of the track along its longitudinal axis, α is the coefficient of linear thermal expansion (a material property), ΔT is the temperature change, and T is the nominal temperature. The length change ΔL can be calculated based on the full width or full length of the track system. For large track systems using multiple compliant track elements to buffer deformation, the required expansion or contraction for each compliant track can be calculated by dividing the total length change by the number of compliant track elements along that dimension.

[0108] Once the required deformation and maximum allowable stress are known, the compliant track element can be modeled (e.g., using the finite element method) to ensure that the design of the track element with staggered slots is suitable for the required fatigue life. Using the finite element method, the required deformation can be applied to the model of the track element, and the stress throughout the material can be calculated. If the calculated stress is too high (exceeding the maximum allowable stress), the design can be modified and the analysis repeated until a design with stresses below the maximum allowable stress is found. Design parameters that can be modified include the number of slots, slot width, slot length, slot spacing, the profile of the slot closure end, the distance between the slot closure end and the side of the track element, and the material used.

[0109] One design approach is to maximize the deformation of each slot within fatigue and elastic limits. This can be achieved by approaching the maximum allowable stress from either direction: one can start with a design that is too stressed and then modify the design to reduce the stress as described above, or one can start with a design that is below the maximum allowable stress and then modify the design to increase the stress. Trade-offs must be made between stress and other design objectives; for example, increasing the stress while keeping it low enough to meet fatigue life requirements results in a design that is easier to manufacture (e.g., with fewer or wider slots). The challenge of finding the optimal design lies in balancing different (and sometimes conflicting) design objectives to create a design that appropriately balances stress, expected life, noise and vibration performance, cost, and ease of manufacture.

[0110] Materials and Manufacturing

[0111] Tracks can be made from any suitable material, including metals such as aluminum. Because tracks are elongated elements with a constant cross-section along their length, they can therefore be formed by extrusion. Alternatively, track elements can be cast.

[0112] Plastic is another material option; it is less expensive and easier to deform, but more prone to wear and tear.

[0113] The slot can be formed by machining, water jet cutting or laser cutting, electrical discharge machining (EDM) or any other suitable method.

[0114] Track systems with compliant track elements

[0115] Figure 17 A track system 13 comprising four sections 88 is schematically shown, wherein several sections are engaged by links 86. Links 86 include compliant track elements 50, thus also possessing compliantness, and the several sections 88 of the track system 13 are movable relative to each other. The track element in each section 88 of the track system 13 is a rigid track element.

[0116] Each of the four segments 88 of the track system 13 includes a first set of tracks 17 extending in a first direction (x-direction) and a second set of tracks 19 extending in a second direction (y-direction), the second direction being substantially perpendicular to the first direction. The four segments 88 of the track system are connected by a link 86 including a compliant track element 50, the compliant track element including staggered slots so that the link 86 itself is compliant.

[0117] As mentioned above, the advantage of dividing the track system into several sections is that—with compliant linkages between the sections—the expansion / contraction that can be performed varies depending on the size of the track system, and the same compliant track elements can be used in track systems of different sizes with different fulfillment centers.

[0118] exist Figure 17 In the illustrated embodiment, the track system 13 is divided into four segments 88, each a 2×2 grid cell. These four 2×2 segments form a track system with a 5×5 grid cell size, where compliant links 86 located between segments 88 form a row and a column of grid cells in the middle of each segment 88. Other sizes of track systems can be formed by different numbers of segments 88, such as 8×8 grid cells formed by nine 2×2 segments, 11×11 grid cells formed by sixteen 2×2 segments, or any other desired size. The same design of track system segments and compliant links can be used for various sizes of track systems, and therefore also for various sizes of grid frame structures and fulfillment centers.

[0119] For ease of illustration, Figure 17 Section 88 of the medium track system is a small section with a 2×2 grid cell. In practice, larger sections (e.g., 20×20, 40×40, or 100×100 grid cells, or any other size) can also be used, and any number of sections in the track system can be joined together by several compliant links to form a track system of the desired size.

[0120] Track support components

[0121] To prevent bending deformation, the compliant track element 50 may be supported below by a horizontal member. The track element may be configured to slide on top of the supporting horizontal member. Alternatively, a sliding bearing may be used.

[0122] Figure 18(a) and (b) illustrate one method of supporting a compliant track element. A compliant track section 50 is supported by a track support 90. Two track supports 90a and 90b support each end of the compliant track element 50, respectively. The track supports 90a and 90b are connected by connecting members 92 located on the sides of the track supports 90. The connecting members 92 may be formed in a single part comprising two elongated segments on either side of the track supports connected by beams, or the connecting members may comprise a pair of members located on either side of the track supports. The connecting members 92 overlap with the track supports 90 along the longitudinal axis of the track supports 90. The track supports 90 include slots 94 that cut into the track supports 90 and extend along the longitudinal axis of the track supports. The track supports 90 are attached to the connecting members 92 by a plurality of sliding blocks 96 disposed within the slots 94. The sliding blocks 96 are connected to the connecting members 92 by a plurality of bolts 98. As the sliding block 96 slides along the length of the slot 94 in the track support 90, this allows the two track supports 90a and 90b to move along their longitudinal axes.

[0123] Figure 18 The sliding arrangement shown in (a and b) allows the compliant track element 50 to expand and contract along its longitudinal axis while restricting movement in any other direction. When the compliant track element 50 expands, the sliding block 96 slides along the slot 94 and allows the two track supports 90a and 90b to move separately. Figure 18 (b) shows two sets of slots and several sliding blocks at different heights, with one sliding block positioned above the other. The advantage of this arrangement is that it helps to limit the movement of the track support along the longitudinal axis.

[0124] although Figure 18 (a) and (b) show four sliding blocks 96 and four slots 94, with one sliding block 96 in each slot 94. However, in other embodiments, different arrangements or numbers of sliding blocks 96 and slots 94 may exist. Each slot may contain more than one sliding block. Figure 18 The slot 94 in (a) and (b) is positioned along the longitudinal axis of the track support 90, but in other embodiments, the positioning of the slot may be different. For example, a pair of parallel slots may be placed on opposite sides of the track support 90. A single slider 96 that moves within a single slot 94 is sufficient to provide relative movement between the two track supports 90a, 90b.

[0125] To reduce wear and facilitate low-friction sliding, the contact surfaces (the outer edge of the sliding block 96 and the inner surface of the slot 94) can be coated with a low-friction material, such as polytetrafluoroethylene (PTFE).

[0126] As Figure 18As an alternative to the sliding arrangement shown, the compliant track element 50 may be placed directly on top of one or more track supports and configured to slide relative to one or more track supports, or the compliant track element 50 may be supported by a sliding bearing, or the track supports may be connected by a pivotal arrangement, or the compliant track element 50 may be supported on rollers arranged on top of one or more track supports, or any other suitable mechanism may be used.

[0127] definition

[0128] In this document, the term “movement in the n-direction” (and related wording) is intended to express a movement substantially along or parallel to the n-axis in any direction (i.e., toward the positive end or the negative end of the n-axis), where n is one of x, y, and z.

[0129] In this document, the word “connect” and its derivatives are intended to include the possibility of direct connection and indirect connection. For example, “x is connected to y” is intended to include the possibility that x is directly connected to y without intermediate components and the possibility that x is indirectly connected to y with one or more intermediate components. When intended to express a direct connection, the terms “directly connected,” “directly connected,” or similar terms are used. Similarly, the word “support” and its derivatives are intended to include the possibility of direct contact and indirect contact. For example, “x supports y” is intended to include the possibility that x directly supports and directly contacts y without intermediate components and the possibility that x indirectly supports y with one or more intermediate components contacting x and / or y. The word “install” and its derivatives are intended to include the possibility of direct installation and indirect installation. For example, “x is installed on y” is intended to include the possibility that x is directly installed on y without intermediate components and the possibility that x is indirectly installed on y with one or more intermediate components.

[0130] In this document, the word "including" and its derivatives are intended to have an open-ended meaning rather than a closed one. For example, "x includes y" is intended to include the possibility that x includes one and only one y, multiple y, or one or more y and one or more other elements. When the intention is to use a closed meaning, "x consists of y" will be used, indicating that c includes only y and no other content.

Claims

1. Storage and retrieval systems, including i) A mesh frame structure, the mesh frame structure comprising: The track system (13) includes a first set of tracks (17) extending along a first direction and a second set of tracks (19) extending along a second direction substantially perpendicular to the first direction, each set of the first set and the second set of tracks (17, 19) including a plurality of track elements; Supporting frame structure, the supporting frame structure supporting the track system (13); and A stack (11) of a plurality of containers (9) is arranged in a plurality of storage columns (10) located below the track system (13); ii) One or more load handling devices (31) for lifting and moving the container (9), each load handling device (31) comprising: Wheel assemblies (35, 37) for moving the load handling device (31) on the track system (13); A container receiving space located above the orbital system (13); Lifting device (43), the lifting device being arranged to lift a single container (9) from the stack (11) to the container receiving space; and A position detection system, the position detection system including a wheel encoder for measuring the speed of one or more wheels in the wheel assembly; The feature is that at least one segment (51) of at least one track element (50) of the first and / or second group of tracks (17, 19) is a compliant track element comprising a plurality of staggered slots (52), the compliant track element defining a top profile configured to be sufficiently smooth to ensure that the wheels of the wheel assembly maintain continuous contact with the track system during movement of the load handling device, thereby mitigating encoder errors caused by loss of wheel traction.

2. The storage and retrieval system of claim 1, wherein, The width of the interlaced slot (52) changes with the deformation of the at least one track element (50).

3. The storage and retrieval system of any preceding claim, wherein, The plurality of interlaced slots (52) extend in a direction substantially perpendicular to the longitudinal direction of the at least one track element (50).

4. The storage and retrieval system according to claim 1 or claim 2, wherein, The slots (52) in the at least one track element (50) are evenly spaced along at least one segment (51) of the at least one track element (50).

5. The storage and retrieval system according to claim 1, wherein, The staggered slots (52) include a first set of slots (62) and a second set of slots (64), the first set of slots (62) and the second set of slots (64) being staggered, each of the first set and the second set of slots having an open end (54) and a closed end (56), wherein the open ends of the first set and the second set of slots (62, 64) are respectively located on opposite sides of the at least one track element (60).

6. The storage and retrieval system according to claim 1, wherein, The staggered slots (52) include a first set of slots (72), a second set of slots (73), and a third set of slots (74). Each slot in the first and second sets of slots (72, 73) has an open end (54) and a closed end (56). The open ends of the first and second sets of slots (72, 73) are located on opposite sides of the at least one track element (70). The third set of slots is a closed-end slot with a closed end, such that the third set of slots (74) is staggered with the first and second sets of slots (72, 73).

7. The storage and retrieval system according to claim 5 or claim 6, wherein, The closed end (56) of the staggered slot (52) has a circular cross-section.

8. The storage and retrieval system according to claim 5 or claim 6, wherein, The closed end (56) of the interlaced slot (52) has a keyhole profile.

9. The storage and retrieval system according to claim 1 or claim 2, comprising a first section and a second section, each section (88) of the first and second sections comprising a first set of tracks (17) extending in a first direction and a second set of tracks (19) extending in a second direction substantially perpendicular to the first direction, wherein the first and second sections (88) of the track system are engaged by a link (86) comprising at least one track element (50), the at least one track element (50) comprising a plurality of staggered slots (52) such that the link (86) between the first and second sections (88) of the track system (13) is compliant.

10. The storage and retrieval system according to claim 1 or claim 2, wherein, The track system (13) includes two or more track elements (50).

11. The storage and retrieval system according to claim 1 or claim 2, wherein, The at least one track element (50) is formed by casting, machining or extrusion.

12. The storage and retrieval system according to claim 1 or claim 2, wherein, The interlaced slots (52) are machined in the at least one track element (50).

13. The storage and retrieval system according to claim 1 or claim 2, wherein, The at least one track element (50) is made of metal or plastic.

14. The storage and retrieval system according to claim 1 or claim 2, wherein, The at least one track element (50) is supported by track supports (90a, 90b), which are connected together by at least one connecting member (92), which is configured to slide relative to at least one of the track supports (90a, 90b) in use, so that the track supports can move relative to each other in the longitudinal direction.

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