Cargo handling device

Abstract

The present invention relates to a load handling device for lifting and moving stacked storage containers in a storage structure. The load handling device comprises a body mounted with a first set of wheels configured to engage a first set of parallel tracks on the storage structure and a second set of wheels configured to engage a second set of parallel tracks on the storage structure. The load handling device further comprises a diverter assembly configured to raise or lower the first set of wheels and the second set of wheels relative to the body to engage one of the first set of wheels or the second set of wheels with the parallel tracks and disengage the other of the first set of wheels or the second set of wheels from the parallel tracks, and a plain bearing assembly comprising a bearing element with a sliding surface that defines a contact line along which the diverter assembly moves relative to the body when raising or lowering the first set of wheels and the second set of wheels.

Description

Technical Field

[0001] The present invention relates to a sliding bearing assembly, and more particularly to a guide bearing assembly for a load handling device.

Background Art

[0002] GB2520104A (Ocado Innovation) describes a system in which stacks of containers are arranged within a storage structure that supports load handling devices. Each load handling device covers one grid space of the storage structure, thus enabling a high throughput of high-density load handlers and thus a system of a given size. The robotic load handling devices are controllably moved around the top of the storage structure on a track system that forms a grid. Each load handling device is configured to lift bins from the stack, and the containers being lifted contain the inventory items necessary to fulfill customer orders. The containers are transported to a pick station where the necessary inventory items may be manually removed from the bins and placed into a delivery container, which forms part of a customer order and is manually packed in due time for shipping.

[0003] Reducing the weight of each load handling device is beneficial. These advantages extend not only to the device itself in terms of reducing capital and operating costs, but also to the surrounding infrastructure such as the storage structure and the track system. However, in order to ensure that a lightweight load handling device is suitable for its intended purpose and continues to function over the desired service life, it is important to minimize harmful vibrations that may compromise its structural integrity over time.

[0004] The present invention has been devised in view of such a background.

Summary of the Invention

[0005] In a first aspect, to form a lattice pattern comprising a plurality of lattice spaces, a handling device for lifting and moving storage containers stacked in a storage structure comprising a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane, wherein the lattice is supported by a set of uprights to form a plurality of vertical storage locations directly below the lattice such that the containers are stacked vertically between the uprights and guided by the uprights, the handling device comprising a body mounted on a first set of wheels configured to engage the first set of parallel tracks and a second set of wheels configured to engage the second set of parallel tracks, a steering assembly configured to raise or lower the first and second sets of wheels relative to the body such that one of the first or second sets of wheels engages the parallel tracks and the other of the first or second sets of wheels disengages from the parallel tracks, and a sliding bearing assembly comprising a bearing element having a sliding surface defining a line of contact along which the steering assembly moves relative to the body when the first and second sets of wheels are raised or lowered. By using the sliding surface to provide a contact area between the steering assembly and the body, noise and vibration are reduced when the steering assembly moves relative to the body as compared to conventional bearing assemblies using rolling bearing elements. The sliding bearing assembly further comprises a removable cartridge configured to hold the bearing element in a predetermined position between the body and the steering assembly, wherein the body or the steering assembly comprises a bearing mount configured to receive the cartridge. This configuration provides two advantages. First, from a maintenance perspective, it provides for easy removal and replacement of the bearing element without the need to disassemble other parts of the bot. Second, by providing a removable cartridge, changes in the dimensions of the contact surface of the sliding bearing assembly (e.g., the diameter of a guide shaft, etc.) can be compensated for.In order to provide smooth and reliable movement during the direction change operation, i.e., movement that is repeatable over time and has little noise and vibration, an accurate fit between the contact surface and the sliding bearing assembly is essential. That is, the distance between the contact surface and the sliding bearing assembly must be accurate because any variation from the nominal dimensions of the contact surface can have the result of causing damage. To accommodate these variations, cartridges of different sizes can be installed to compensate for any changes to the nominal dimensions of the contact surface. Thus, depending on the dimensions of the contact surface, removable cartridges of different sizes can be selected, thereby preventing inaccuracies between the dimensions of the contact surface and reducing the noise and vibration resulting from the direction change operation. Compensating for deviations from the nominal dimensions of the contact surface is not as easily achievable with conventional bearing configurations.

[0006] Optionally, the body or the direction change assembly comprises a bore that allows access to the cartridge within the bearing mount. This configuration allows a removable cartridge to be removed from the bearing mount using an elongated tool such as a screwdriver.

[0007] Optionally, the bore is flared in the direction of the cartridge. This branched configuration allows the narrower opening of the bore to be used as a fulcrum about which an elongated tool can pivot in order to lever the removable cartridge out of the bearing mount.

[0008] Optionally, the cartridge is configured to be removed from the body or the direction change assembly in the direction of the low friction contact line. This means that, in contrast to the cartridge applying torque to the bearing elements and screwing them in their positions within the cartridge, pushing or pulling the bearing elements across the minor axis of the sliding surface, the cartridge can be slid into or out of the bearing mount along the major axis of the sliding surface of the bearing elements.

[0009] Optionally, the sliding bearing assembly further comprises a retaining plate that can be fixed to the body or the direction-changing assembly so as to hold the cartridge in place with respect to the body or the direction-changing assembly. The use of the retaining plate provides an easy means for holding the sliding bearing assembly together and fixing it in a predetermined position on the body or the direction-changing assembly.

[0010] Optionally, the sliding bearing assembly further comprises a fastener that extends through the retaining plate and the cartridge.

[0011] Optionally, the cartridge comprises a manual adjustment mechanism configured to adjust the position of the bearing element with respect to the cartridge. Alternatively, the cartridge is marked according to its size to facilitate identification.

[0012] Optionally, the bearing element has a cylindrical shape. As an alternative option, the bearing element has a triangular prism shape. In the latter option, the low-friction contact line is preferably positioned at the apex of the bearing element.

[0013] Optionally, the bearing element is made of polytetrafluoroethylene (PTFE).

[0014] In a second aspect, a sliding bearing assembly for use with a load handling device according to the first aspect is provided.

[0015] These and other aspects of the invention will be described by way of example only with reference to the accompanying drawings.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0017] In the drawings, like features are indicated by like reference numerals as necessary.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The following embodiments represent preferred examples of how to implement the present invention, but they are not necessarily the only examples of how this can be achieved. These examples are described in sufficient detail so that those skilled in the art can implement the present invention. Other examples may be utilized and structural changes may be made without departing from the scope of the present invention as defined in the appended claims. Further, references to directions and any other terms having an implicit orientation are provided as examples to assist the reader of the particular examples described herein. They should not be read as requirements or limitations, particularly with respect to the position, orientation, or use of the present invention, unless specifically recited in the appended claims. Similarly, references to connections (e.g., attached, coupled, connected, joined, fixed, etc.) should be construed broadly and may include intermediate members between the connection of elements and relative movement between elements. Thus, a reference to a connection does not necessarily mean that two elements are directly connected and in a fixed relationship to each other, unless specifically recited in the appended claims. Similarly, the phrase "movement in the n direction" and equivalent expressions where n is one of x, y, and z are intended to mean movement substantially along or parallel to the n axis in either direction (i.e., the direction towards the positive end of the n axis or the direction towards the negative end of the n axis).

[0019] FIG. 1 illustrates a storage structure 1 including an upright member 3 and horizontal members 5, 7 supported by the upright member 3. The horizontal members 7 extend parallel to each other along the illustrated x axis, while the horizontal member 5 extends parallel to each other along the illustrated y axis and laterally with respect to the horizontal member 7. The upright members 3 extend parallel to each other and to the illustrated z axis. The horizontal members 5, 7 form a grid pattern defining a plurality of grid cells. In the illustrated example, the container 9 is disposed in a stack 11 below the grid cells defined by the grid pattern, with one stack 11 of the container 9 per grid cell.

[0020] Figure 2 shows an enlarged plan view of a section of a track structure 13, generally designated 13, which is positioned at the uppermost part of the horizontal members 5, 7 and forms part of the storage structure 1 shown in FIG. 1. The track structure 13 may be provided by the horizontal members 5, 7 themselves (e.g., formed within or on the surface of the horizontal members 5, 7) or by one or more additional components attached to the uppermost part of the horizontal members 5, 7. The illustrated track structure 13 has an x-direction track 17 and a y-direction track 19. In this case, the first set 17 of tracks extends in the x-direction and the second set 19 of tracks extends in the y-direction across the first set 17 of tracks. The tracks 17, 19 define an aperture 15 at the center of the grid cell. The aperture 15 is sized to allow a container 9 located below the grid cell to be lifted and lowered through the aperture 15. The first set 17 of tracks is provided in pairs separated by a ridge 21, and the second set 19 of tracks is provided in pairs separated by a ridge 23. Other arrangements of the track structure may be possible.

[0021] Figure 3 shows a plurality of load handling devices 31 moving over the uppermost part of the storage structure 1 shown in FIG. 1. Each load handling device 31, which may also be referred to as a robot 31 or a bot 31, is provided with a set of wheels for engaging the corresponding x-direction track 17 or y-direction track 19 to allow the direction-changing assembly (not shown) and the bot 31 to move across the track structure 13 and reach a particular grid cell. As described above, the sets of tracks 17, 19 are separated by ridges 21, 23 that allow a pair of bots 31 to pass through each other without occupying or colliding with adjacent grid cells.

[0022] As shown in detail in FIG. 4, the bot 31 includes a body 33 in or to which one or more components are attached that enable the bot 31 to perform its intended functions. These functions may include moving over the storage structure 1 on the track structure 13 and raising or lowering the container 9 to or from the stack 11, whereby the bot 31 can place or retrieve the container 9 at a specific location defined by the grid pattern. To perform the latter function, the bot 31 includes container lifting means 39 configured to lift the container 9 from the stack 11 into the container receiving space or cavity of the bot 31 and lower the container 9 from the container receiving space onto the stack 11. The illustrated container lifting means 39 includes four tapes or reels 41, which are connected at their lower ends to a container gripping assembly 43. The container engagement assembly 43 includes engagement means configured to engage features of the container 9 (which may be provided, for example, at the corners of the container engagement assembly 43 in the vicinity of the tapes 41). For example, the containers 9 may be provided with one or more apertures in their upper sides into which the engagement means can engage. Alternatively or additionally, the engagement means may be configured to hook under the rim or lip of the container 9 and / or clamp or grip the container 9. The tapes 41 may be wound up or down as required to raise or lower the container engagement assembly. One or more motors or other means may be provided to wind or control the winding of the tapes 41. In an alternative embodiment, the container receiving space of the bot 31 may not be within the body 33 of the bot 31. For example, in some embodiments, the container receiving space may be adjacent to the body 33 of the bot 31 (e.g., in a cantilever configuration having the weight of the body 33 of the bot 31 that balances the weight of the container to be lifted).In such an embodiment, the frame or arm of the container lifting means 39 may project horizontally from the body 33 of the bot 31, and the tapes / reels 41 may be arranged at respective positions on the projecting frame and configured to be raised and lowered from those positions to raise and lower the container 9 within the container receiving space adjacent to the body 33. The height at which the frame is attached to and projects from the body 33 of the bot 31 may be selected to provide the desired effect. For example, the frame preferably projects at a high level on the body 33 of the bot 31 such that a relatively large container or a plurality of containers can be lifted into the container receiving accommodation space below the frame. Alternatively, the frame may be arranged to project lower below the body 33 (but at a height sufficient to accommodate at least one container between the frame and the track structure 13) in order to keep the center of mass of the bot 31 lower when the bot 31 is loaded with containers.

[0023] The bot 31 comprises a first set 35 of wheels and a second set 37 of wheels, which are attached to the body 33 of the bot 31 and enable the bot 31 to move along the tracks 17 and 19 in the x - direction and y - direction respectively. In particular, two wheels 35 are provided on the shorter side of the bot 31 visible in FIG. 4, and a further two wheels 35 are provided on the opposite shorter side of the bot 31. The wheels 35 engage with the track 17 and are rotatably attached to the body 33 of the bot 31 to enable the bot 31 to move along the track 17. Similarly, two wheels 37 are provided on the longer side of the bot 31 visible in FIG. 4, and a further two wheels 37 are provided on the opposite longer side of the bot 31. The wheels 37 engage with the track 19 and are rotatably attached to the body 33 of the bot 31 to enable the bot 31 to move along the track 19.

[0024] The steering assembly, designated as 44 in its entirety, enables the bot 31 to move in first and second directions over different wheels 35, 37, and selectively engages the first set of wheels 35 with the first set of tracks or the second set of wheels 37 with the second set of tracks 19 of the storage structure 1. The steering assembly 44 may be driven by a single motor (not shown) and 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 enabling the load handling device 31 to selectively move in either the first or second direction across the tracks 17, 19 of the storage structure 1.

[0025] As shown in FIG. 5, the steering assembly 44 includes four wheel mounts 48 to which the first and second sets 35, 37 of wheels are attached. One wheel mount 48 is provided at each of the opposite short sides 36 of the bot 31, and the two remaining wheel mounts 48 are provided at the long sides 38 respectively. Each wheel mount 48 is configured to move substantially vertically to raise or lower the first and second sets 35, 37 of wheels relative to the body 33 of the bot 31, whereby one of the first or second sets 35, 37 of wheels is engaged with the parallel tracks 17, 19 and the other of the first or second sets 35, 37 of wheels is disengaged from the parallel tracks 17, 19. To perform this operation, the steering assembly 44 further includes four horizontal traversers 46 connected to the respective wheel mounts 48 via a set of link mechanisms 50. The horizontal traversers 46 are configured to shift laterally along the horizontal guide rails 52 under the force applied to pull the respective wheel mounts 48 upward or push them downward through the set of link mechanisms 50. This operation is schematically illustrated in FIGS. 6a and 6b showing some parts of the steering assembly 44 associated with one of the longer side portions 38 of the bot 31. However, it will be understood that the equivalent parts of the steering assembly 44 associated with the different sides 36, 38 of the bot 31 function similarly. Referring to FIG. 6a, when a first lateral force is applied to the horizontal traverser 46, in this example applied in the right direction, the horizontal traverser 46 moves in the right direction. This rightward movement angles the set of link mechanisms 50 slightly away from the vertical and converts it into a vertical movement that directs the wheel mount 48 downward relative to the horizontal traverser 46, engaging the two wheels of the second set 37 of wheels related to this side portion 38 of the bot 31 with the second set of tracks 19 and supporting the body 33 above the parallel tracks 17, 19. In the example shown in FIG. 6b, when a second lateral force directed to the left is applied to the horizontal traverser 46, the horizontal traverser 46 is moved leftward along the horizontal guide rail 52.The degree of movement in the left direction is relatively larger than the movement in the right direction that the horizontal traveler 46 undergoes under the first lateral force. As a result, compared to the example shown in FIG. 6a, the set of link mechanisms 50 is angled further away from the vertical and, of course, the vertical distance between the horizontal traveler 46, which remains in a fixed vertical position relative to the main body 33, and the wheel mount 48 is relatively decreased. That is, in this example, the leftward movement of the horizontal traveler 46 is converted into a vertical movement that directs the wheel mount 48 upward relative to the horizontal traveler 46, disengaging the two wheels of the second set 37 of wheels from the second set 19 of tracks. With this configuration, by converting the lateral movement of the horizontal traveler 46 into the vertical movement of each wheel mount 48, the direction-changing assembly 44 is configured to lower and raise the first and second sets 35, 37 of wheels to engage and disengage the parallel tracks 17, 19.

[0026] Referring to FIG. 7, the body 33 includes four substantially vertical guide shafts 54, each shaft 54 being positioned at each corner of the bot 31. The ends of the wheel mounts 48 are slidably attached to the guide shafts 54, and the guide shafts 54 function to guide the vertical movement of the wheel mounts 48 during a direction change operation. This sliding engagement between the wheel mounts 48 and the guide shafts 54 is provided in this example by a plurality of sliding bearing assemblies 56 fixed to the wheel mounts 48. Specifically, in this embodiment, each wheel mount 48 includes four sliding bearing assemblies 56, two at each end. The sliding bearing assemblies 56 are configured to define channels 58 into which the guide shafts 54 are received. Each assembly 56 includes at least one bearing element 60 having a sliding surface that defines a low friction contact line between the wheel mount 48 and the guide shaft 54, and when raising or lowering the first and second sets 35, 37 of wheels, the wheel mount 48 moves along the sliding surface relative to the guide shaft 54. The bearing element 60 may be made of polytetrafluoroethylene (PTFE) or any other material having a similarly low coefficient of friction. Referring to FIG. 8, in this example, each of the sliding bearing assemblies 56 fixed to the wheel mount 48 includes three bearing elements 60. The bearing elements 60 are equally spaced around the guide shaft 54 so as to more evenly distribute any load that the sliding bearing assembly 56 receives during a direction change operation. The bearing elements 60 are oriented such that their longitudinal axes extend in the direction of movement between the wheel mount 48 and the guide shaft 54, and in this example, to provide stability to the wheel mount 48 during a direction change operation, while maximizing the contact area in the direction of their longitudinal axes and reducing the extent of the tangential contact area of the sliding surface, they have a cylindrical shape. Of course, it will be understood that bearing elements 60 of other shapes can be used for the sliding bearing assemblies 56. One such example is a bearing element 60 having a triangular prism shape and positioned such that a low friction contact line providing a connection between the guide shaft 54 and the wheel mount 48 is located along one of its vertices.

[0027] The bearing element 60 is held within one or more removable cartridges 62 that form part of the sliding bearing assembly 56. In the example shown in FIG. 8, the sliding bearing assembly 56 includes two removable cartridges 62 for holding the bearing element 60 in a predetermined position between the guide shaft 54 and the wheel mount 48. In this example, the cartridges 62 are arranged such that one holds a single bearing element 60 and the other holds two bearing elements 60. The removable cartridges 62 are received within respective bearing mounts 57 that form part of the wheel mount 48 in this example. The use of the removable cartridges 62 has two main advantages. First, from a maintenance perspective, it provides for easy removal and replacement of the bearing element 60 without the need to disassemble other parts of the bot 31. This is particularly true in this example where the removable cartridge 62 and the bearing mount 57 are configured such that the cartridge 62 can be lifted upward from the bearing mount 57 and pushed downward into the bearing mount 57 in a direction substantially the same as the longitudinal axis of the bearing element 60. This means that, in contrast to pushing or pulling across the minor axis of the sliding surface of the bearing element 60, which would apply torque to the bearing element 60 and twist their positions within the cartridge 62, the cartridge 62 can be slid into and out of the bearing mount 57 along the major axis of the sliding surface of the bearing element 60. Second, by providing the removable cartridges 62, changes in the diameter of the guide shaft 54 can be compensated for. As described above, the sliding bearing assembly 56 defines channels 58 into which the guide shaft 54 is received, and these channels 58 are primarily defined by the removable cartridges 62 together with the bearing elements 60. An exact fit between the guide shaft 54 and the sliding bearing assembly 56 is essential to provide smooth and reliable movement during the direction change operation, i.e., movement that is repeatable over time and has little noise and vibration. That is, the distance between the guide shaft 54 and the sliding bearing assembly 56 must be exact because variations from the nominal diameter of the guide shaft 54 can have damaging consequences for each guide shaft 54.Also, such variations do not necessarily have to be outside the expected tolerances of the guide shaft 54 (e.g., +-0.5 mm) that would cause a negative effect. To accommodate these variations, cartridges 62 of different sizes can be attached to the wheel mount 48, defining a larger or smaller channel 58 that receives the guide shaft 54 according to the size of the shaft 54 while fitting precisely within the bearing mount 57. Thus, removable cartridges 62 of different sizes can be selected according to the size of the guide shaft 54 in which they are used, preventing inaccuracies between them and reducing noise and vibration resulting from the direction change operation. Also, cartridges of different sizes can be marked according to their respective sizes to facilitate identification. Compensating for deviations from the nominal diameter of the guide shaft 54 cannot be easily done with conventional bearing configurations. As an alternative to using cartridges 62 having different sizes, each cartridge 62 may instead be provided with a manual adjustment mechanism configured to adjust the position of one or more bearing elements 60 that hold against itself, bringing the bearing elements 60 of the sliding bearing assembly 56 closer together or farther apart.

[0028] The sliding bearing assembly 56 further includes a retaining plate 64 that can be fixed to the wheel mount 48 so as to hold a removable cartridge 62 in a predetermined position within the bearing mount 57 during use. In this embodiment, each sliding bearing assembly 56 includes two retaining plates 64, one for each of the removable cartridges 62. Each retaining plate 64 is positioned at the top of its respective removable cartridge 62 and is held in place by one or more fasteners 66, including threaded screws in this example. The retaining plate 64 and the removable cartridge 62 each include one or more open bores 68, and the bearing mount 57 includes one or more threaded closed bores 70. The bores 68, 70 are positioned such that they are aligned when the removable cartridge 62 and the retaining plate 64 are assembled within the bearing mount 57. This configuration allows the fasteners 66 to extend through the removable cartridge 62 and the retaining plate 64 and be fixed within the threaded bore 70 to hold the assembly 56 together. To remove the removable cartridge 62 from the bearing mount 57, the associated fastener 66 is loosened and the associated retaining plate 64 is lifted from the removable cartridge 62. The removable cartridge 62 itself can then be removed from the bearing mount 57. To facilitate pulling the removable cartridge 62 out of the bearing mount 57, the bearing mount 57 includes one or more access bores 72 through which an elongated tool, such as a screwdriver, can be used to access the removable cartridge 62 and pull it out of the bearing mount 57. The access bore 72 extends from the outer surface of the wheel mount 48 to the side surface of the bearing mount 57 and flares in the direction of the removable cartridge 62. That is, the cross-sectional area of the access bore 72 increases in the direction of the bearing mount 57. This branched arrangement allows the narrower opening of the access bore 72 on the outer surface of the wheel mount 48 to be used as a pivot point around which an elongated tool can pivot to pull the removable cartridge 62 out of the bearing mount 57 with a lever.

[0029] The sliding bearing assembly 56 of this example includes three bearing elements 60 positioned at equal intervals around the guide shaft 54. This arrangement is schematically shown in FIG. 9a, although other configurations are of course envisioned. In this example, the bearing elements 60 are held within two removable cartridges 62, with one cartridge 62 holding a single bearing element 60 and the other holding two bearing elements 60. However, the choice of how many removable cartridges 62 and bearing elements 60 are used is highly dependent on the available space around the guide shaft 54 and is not limited to the specific examples shown herein. For example, referring to FIG. 9b, the sliding bearing assembly 56 can include four bearing elements 60 each held within their respective cartridges 62. Alternatively, the four bearing elements 60 may be held within two removable cartridges 62 each carrying two bearing elements 60, or one cartridge 62 may carry a single bearing element 60 and the other carry the remaining three bearing elements 60. In further examples shown in FIGS. 9c and 9d, the sliding bearing assembly 56 may include five or six bearing elements 60 positioned at equal intervals around the guide shaft 54, and the bearing elements 60 are held within two or more removable cartridges 62. Thus, the advantages of the sliding bearing assembly 56 described above can be achieved regardless of the number and arrangement of the bearing elements 60 and the removable cartridges 62.

[0030] In this regard, the sliding bearing assembly 56 has been described in the context of providing a sliding engagement between the wheel mount 48 and the guide shaft 54. However, a variant of the sliding bearing assembly 56 may be used to provide a sliding engagement between other components of the direction-changing assembly 44 and the body 33 of the bot 31. Specifically, the sliding bearing assembly 56 can be used between the horizontal traveler 46, which forms part of the direction-changing assembly 44, and the horizontal guide rail 52, which is part of the body 33 of the bot 31. Referring to FIGS. 10a and 10b, as described above, the horizontal traveler 46 is driven left or right along each horizontal guide rail 52 to raise or lower the first or second set 35, 37 of wheels. Each horizontal traveler 46 includes four sliding bearing assemblies 56, and two of the assemblies 56 are positioned on both sides of the horizontal traveler 46 (shown in FIG. 10b without their respective retaining plates 64). In this configuration, two of the four sliding bearing assemblies 56 slidably engage and support the horizontal traveler 46 on the upper horizontal guide rail 52, and the remaining two sliding bearing assemblies 56 slidably engage and support the horizontal traveler 46 on the lower horizontal guide rail 52. Each sliding bearing assembly 56 includes two bearing elements 60 having respective sliding surfaces, and each of the sliding surfaces defines a low-friction contact line along which the horizontal traveler 46 moves relative to the horizontal guide rail 52 when raising or lowering the first set 35 of wheels or the second set 37 of wheels.

[0031] Referring to FIG. 11, the bearing assembly 56 used for the horizontal traveler 46 is substantially the same as that used for the wheel mount 48, and each includes a removable cartridge 62 housed within a bearing mount 57 of the horizontal traveler 46. The removable cartridge 62 holds two elongated bearing elements 60 that extend in the direction in which the horizontal traveler 46 moves and is configured to provide a low-friction contact line that extends in the same direction. The bearing elements 60 are held in place within the removable cartridge 62 by a retaining plate 64 disposed on top of the removable cartridge 62. The retaining plate 64 includes a hooked arm 74 that extends rearward through the removable cartridge 62 when the bearing assembly 56 is assembled. The hooked arm 74 engages a fixing bolt 76 disposed to penetrate the horizontal traveler 46 and the removable cartridge 62 and is configured to hold the assembly 56 in place during use. This variant of the sliding bearing assembly 56 has all of the attendant advantages provided by the variant used for the wheel mount 48. That is, they provide a low-friction contact line along which the direction-changing assembly 44 moves relative to the body 31 and reduce the noise and vibration resulting from the direction-changing operation as compared to known bearing configurations. Further, by providing the removable cartridge 62, the bearing elements 60 can be easily removed and replaced without the need to disassemble other parts of the bot 31, and it becomes possible to compensate for changes in the diameter of the guide rail 52.

[0032] The present invention is described only by way of example, and it will be understood by those skilled in the art that various alternative approaches can be adopted without departing from the scope of the invention as defined by the appended claims. For example, the sliding bearing assembly 56 is shown attached to the steering assembly 44 (i.e., the wheel mount 48 and the horizontal traveler 46, both of which form part of the steering assembly 44), and the steering assembly 44 provides a low-friction contact line for movement relative to the body 33 of the bot 31. This sliding engagement between the steering assembly 44 and the body 33 of the bot 31 is provided by a variation of the sliding bearing assembly 56 disclosed herein, although other embodiments are envisioned where the sliding bearing assembly 56 is attached to the body 33 of the bot 31 as opposed to the steering assembly 44. The invention described in the original claims of the present application is appended below. [1] A cargo handling device for lifting and moving storage containers stacked in a storage structure, comprising a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane to form a grid pattern with a plurality of grid spaces, wherein the containers are stacked vertically between uprights through the plurality of grid spaces and guided by the uprights, and the grid is supported by a set of uprights to form a plurality of vertical storage locations below the grid. The cargo handling device has a body attached to a first set of wheels configured to engage a first set of parallel tracks and a second set of wheels configured to engage a second set of parallel tracks, a steering assembly configured to raise or lower the first and second sets of wheels relative to the body so that one of the first or second sets of wheels engages the parallel tracks and the other of the first or second sets of wheels disengages from the parallel tracks, and a sliding bearing assembly, the sliding bearing assembly comprising a bearing element having a sliding surface defining a contact line along which the steering assembly moves relative to the body when the first and second sets of wheels are raised or lowered, and a removable cartridge configured to hold the bearing element in a predetermined position between the body and the steering assembly, wherein the body or the steering assembly comprises a bearing mount configured to receive the cartridge, a cargo handling device. [2] The cargo handling device according to [1], wherein the body or the steering assembly comprises a bore through which access to the cartridge is possible. [3] The cargo handling device according to [2], wherein the bore extends in the direction of the cartridge. [4] The cartridge is configured to be removed from the main body or the direction-changing assembly in the direction of the contact line, the load handling device according to any one of [1] to [3]. [5] The sliding bearing assembly further includes a holding plate fixable to the main body or the direction-changing assembly so as to hold the cartridge at a predetermined position with respect to the main body or the direction-changing assembly, the load handling device according to any one of [1] to [4]. [6] The sliding bearing assembly further includes a fastener extending through the holding plate and the cartridge, the load handling device according to [5]. [7] The cartridge includes a manual adjustment mechanism configured to adjust the position of the bearing element with respect to the cartridge, the load handling device according to any one of [1] to [6]. [8] The cartridge is marked according to its size to facilitate identification, the load handling device according to any one of [1] to [7]. [9] The bearing element has a cylindrical shape, the load handling device according to any one of [1] to [8].

[10] The bearing element has a triangular prism shape, the load handling device according to any one of [1] to [8].

[11] The contact line is positioned at the apex of the bearing element, the load handling device according to

[10] .

[12] The bearing element is made of polytetrafluoroethylene, the load handling device according to any one of [1] to

[11] .

[13] A sliding bearing assembly for use with the load handling device according to any one of [1] to

[12] .

Claims

1. A load handling device for lifting and moving stacked storage containers in a storage structure, comprising a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane, for forming a grid pattern with a plurality of grid spaces, wherein the container is stacked vertically between uprights through the plurality of grid spaces and guided by the uprights, and the grid is supported by a set of uprights to form a plurality of vertical storage locations under the grid, The load handling device is attached to a body and a first set of wheels configured to engage a first set of parallel tracks and a second set of wheels configured to engage a second set of parallel tracks, a direction changing assembly configured to raise or lower the first and second sets of wheels relative to the body so as to engage one of the first or second sets of wheels with the parallel tracks and disengage the other of the first or second sets of wheels from the parallel tracks, and a sliding bearing assembly, the sliding bearing assembly comprising a bearing element having a sliding surface defining a contact line along which the direction changing assembly moves relative to the body when raising or lowering the first and second sets of wheels, and a removable cartridge configured to hold the bearing element at a predetermined position between the body and the direction changing assembly, wherein the body or the direction changing assembly comprises a bearing mount configured to receive the cartridge, a load handling device.

2. The load handling device according to claim 1, wherein the body or the direction changing assembly comprises a bore through which access to the cartridge is possible.

3. The load handling device according to claim 2, wherein the bore extends in the direction of the cartridge.

4. The load handling device according to claim 1, wherein the cartridge is configured to be removed from the body or the direction changing assembly in the direction of the contact line.

5. The load handling device according to claim 1, wherein the sliding bearing assembly further comprises a holding plate fixable to the body or the direction changing assembly so as to hold the cartridge in a predetermined position with respect to the body or the direction changing assembly.

6. The load handling device according to claim 5, wherein the sliding bearing assembly further comprises a fastener extending through the holding plate and the cartridge.

7. The load handling device according to claim 1, wherein the cartridge comprises a manual adjustment mechanism configured to adjust the position of the bearing element with respect to the cartridge.

8. The load handling device according to claim 1, wherein the cartridge is marked according to its size to facilitate identification.

9. The load handling device according to claim 1, wherein the bearing element has a cylindrical shape.

10. The load handling device according to claim 1, wherein the bearing element has a triangular prism shape.

11. The load handling device according to claim 10, wherein the contact line is positioned at the apex of the bearing element.

12. The load handling device according to claim 1, wherein the bearing element is made of polytetrafluoroethylene.

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