Slip sheet

Abstract

A slip sheet (56) for placement between layers of storage containers on a pallet to prevent relative slippage between the layers. The slip sheet (56) comprises a plurality of seats (58), each seat being shaped and sized to accommodate a respective storage container. The plurality of seats are arranged in a pattern that is rotationally symmetrical about a centre of the slip sheet. A plurality of engagement features (60a, 60b) are configured to enable a robotic end effector to engage with and lift the slip sheet. A marker (62) has a rotational symmetry that is a factor of the rotational symmetry of the pattern of seats and which shares the same rotational axis. The marker comprises orientation elements detectable by a vision system for determining the rotational orientation of the slip sheet and thereby, the orientation of the plurality of seats.

Description

[0001] SLIP SHEET

[0002] Technical Field

[0003] The present disclosure relates to slip sheets for use with palletized storage containers, and more particularly to slip sheets having features that facilitate automated handling and positioning by robotic systems.

[0004] Background

[0005] Palletized storage systems form a standard component of modem warehousing, distribution, and logistics operations. These systems rely on pallets as platforms for organizing and transporting goods. Containers are typically arranged on pallets in multiple layers to maximize storage density and facilitate efficient space utilization. The stacked configuration requires consideration of structural stability and proper organization to enable safe handling and transport. Various industries employ palletized storage for products ranging from food and beverages to manufactured goods and raw materials.

[0006] Maintaining stability between layers of stacked containers presents technical challenges during transport and handling operations. Vibration, acceleration, and deceleration forces can cause relative movement between layers, potentially leading to misalignment or structural failure of the stack. Layer separation has traditionally been addressed through various means, including intermediate sheets or other materials placed between layers. These intermediate layers serve to distribute loads and create defined boundaries between container layers. The selection and placement of such materials affects both the stability of the stack and the ease of subsequent handling operations.

[0007] Manual palletizing and depalletizing operations require workers to position containers and any intermediate materials by hand. These processes involve repetitive lifting, precise placement, and coordination to achieve proper alignment across each layer. The time required for manual operations scales with the number of layers and containers, affecting throughput in facilities handling large volumes. Consistency in placement depends on worker skill and attention, with variations potentially affecting stack stability. Automation of material handling has become increasingly adopted infacilities seeking to improve throughput, reduce labour costs, and achieve more uniform results.

[0008] Automated palletizing systems must address several technical requirements to function reliably. Sensing mechanisms may be employed to determine the position of components before placement. Robotic handling equipment requires appropriate design to manipulate different types of components during palletizing operations. System design involves trade-offs between the use of specialized handling mechanisms for each component type and more versatile mechanisms capable of manipulating multiple component types. The complexity of the handling system affects both initial implementation costs and ongoing operational considerations such as changeover time and maintenance requirements.

[0009] Summary

[0010] A slip sheet is provided for placement between layers of storage containers on a pallet to prevent relative slippage between the layers. The slip sheet comprises a plurality of seats, each seat being shaped and sized to accommodate a respective storage container. The term “storage container” as used herein is intended to be construed broadly and includes any article, receptacle, carrier, or support structure capable of holding, transporting, or storing goods. Such storage containers may include, without limitation, cases, trays, boxes, bins, totes, crates, cartons, or similar handling units.

[0011] The geometry of each seat may be configured to correspond to the footprint, base profile, or support features of the storage container to be accommodated. The seats may therefore be adapted for containers of differing shapes, dimensions, and structural configurations without departing from the scope of the present disclosure.

[0012] The plurality of seats are arranged in a pattern that is rotationally symmetrical about a centre of the slip sheet. The slip sheet further comprises a plurality of engagement features configured to enable a robotic end effector to engage with and lift the slip sheet. A marker is provided having a rotational symmetry that is a factor of the rotational symmetry of the pattern of seats and which shares the same rotational axis. The marker comprises orientation elements detectable by a vision system for determining the rotationalorientation of the slip sheet and thereby, the orientation of the plurality of seats. Optionally, the pattern of seats exhibits a four-fold rotational symmetry and the marker exhibits a two-fold rotational symmetry. Optionally, the rotational symmetry of the marker coincides with the rotational symmetry of the pattern of seats, i.e., the factor could be one, e.g., the pattern of seats and the maker has a four-fold rotational symmetry. For the purpose of the present disclosure, the rotational symmetry of the marker aligns with the rotational symmetry of the pattern of seats, i.e., the axis (or axes) about which the marker is rotationally symmetric are the same axis (or axes) about which the pattern of seats is rotationally symmetric. The rotational symmetry of the marker may be a wholenumber factor of the rotational symmetry of the pattern of seats. If the pattern of seats exhibits rotational symmetry of order n, the marker may exhibit rotational symmetry of order m, where m is a positive integer factor of n (1 < m < n). By way of example, where the pattern of seats exhibits four-fold rotational symmetry, the marker may exhibit onefold, two-fold, or four-fold rotational symmetry. This configuration allows automated systems to accurately identify the orientation of the slip sheet and its seats, facilitating precise placement of storage containers by robotic handling equipment.

[0013] The present disclosure further provides a robotic material handling system comprising:

[0014] a robotic end effector configured to engage with storage containers;

[0015] a vision system configured to detect the orientation of a slip sheet according to the present invention; and

[0016] control system comprising one or more processors and memory storing instructions that when executed by the one or more processors cause the one or more processors to orient and position the slip sheet and / or storage containers based on the detected orientation of the marker.

[0017] Preferably, the robotic end effector is configured to engage with both the storage containers and the slip sheet using a common engagement mechanism. Optionally, the common engagement mechanism comprises a lifting frame and a plurality of gripper elements.

[0018] The present disclosure further provides a method of positioning a slip sheet according to the present disclosure between layers of storage containers on a pallet, comprising:detecting a marker on the slip sheet using a vision system;

[0019] determining an orientation of the slip sheet based on the detected marker; gripping the slip sheet using a robotic end effector that engages with the plurality of engagement features on the slip sheet; and

[0020] placing the slip sheet onto a layer of storage containers such that the plurality of seats on the slip sheet are aligned with the storage containers below.

[0021] Brief Description of the Figures

[0022] Examples of the present disclosure will now be described with reference to the accompanying drawings:

[0023] Figure 1 is a schematic diagram showing a distribution network for fulfilling customer orders;

[0024] Figure 2 is a perspective view showing a storage and retrieval system comprising a grid framework structure;

[0025] Figure 3 is a perspective view showing a load handling device positioned above a storage container;

[0026] Figures 4(a and b) are schematic perspective cut away views of the load handling device of Figure 4 showing (a) a container accommodated within the container receiving space of the load handling device and (b) the container receiving space of the load handling device.;

[0027] Figure 5 is a perspective view showing a load handling device with a grabber device positioned above a storage container;

[0028] Figure 6 is a perspective view showing a storage and retrieval system with a pallet transfer station comprising a de-palletising station and a consolidation station;

[0029] Figure 7 is a perspective view showing storage containers arranged in multiple layers on a pallet with slip sheets interposed between the layers;Figures 8(a and b) are perspective views showing a slip sheet with depressions arranged in a rotationally symmetric pattern, where (a) show a top plan view of the slip sheet; and (b) the underside of the slip sheet;

[0030] Figures 9(a and b) are perspective views showing a robotic arm comprising an end effector configured to engage with a slip sheet, where (a) show the end effector attached to a six axes robot; and (b) show the end effector engaged with a set of engagement features of the slip sheet;

[0031] Figures 10(a and b) are perspective views showing an end effector with gripper elements configured to engage with storage containers and slip sheets, where (a) show an isometric view of the end effector; and (b) show the underside of the end effector;

[0032] Figure 11 is a top plan view showing a slip sheet with a marker disposed at the geometric centre and a plurality of seats arranged in a pinwheel pattern.

[0033] Figure 12 is a top plan view showing a slip sheet with a cruciform marker exhibiting two-fold rotational symmetry and seats arranged in a pattern exhibiting fourfold rotational symmetry.

[0034] Figure 13 is a perspective view showing the separation between adjacent slip sheets in a stack by one or more separator elements.

[0035] Detailed Description

[0036] Figure 1 shows schematically a distribution network 2 for fulfilling customer orders. The distribution network 2 comprises a re-distribution centre 4 and a plurality of customer fulfilment centres 6. The re-distribution centre 4 is arranged to receive goods 8 from suppliers via delivery vehicles 10 and to redistribute those goods 8 to the customer fulfilment centres 6 to replenish stock and fulfil demand.

[0037] Goods 8 are typically delivered on pallets 46 in the form of case units stacked in multiple layers. The re-distribution centre 4 includes a staging area for receiving pallets 46 and further incorporates a buffer for temporary storage and sorting of goods prior to consolidation and dispatch. The buffer comprises a storage and retrieval system 11 including a grid framework structure 14, as shown in Figure 2. The grid framework structure 14defines a three-dimensional storage architecture capable of storing storage containers 12 in stacked arrangements within storage columns 13. The grid framework structure 14 comprises upright members 16 supporting horizontal members arranged in a grid pattern to form grid cells. The upright members 16 laterally constrain and vertically guide the storage containers 12 within the storage columns 13, thereby preventing horizontal displacement of stacked containers and enabling high-density storage.

[0038] A track system 22 is supported above the storage columns 13 and comprises rails or tracks extending in orthogonal X and Y directions. The orthogonal rails enable load handling devices 30 to travel in two horizontal directions across the grid framework structure 14 so that a load handling device 30 can be positioned above any selected storage column 13. Each storage container 12 is configured to hold one or more case units or product items and may be formed of plastics material or metal. Storage containers 12 are stacked within the storage columns 13 and are retrieved and deposited under control of a control system coordinating movement of the load handling devices 30.

[0039] Figure 3 illustrates a load handling device 30 movable on the track system 22. The load handling device 30 comprises a vehicle body 32, a first set of wheels 34 configured to engage rails extending in a first direction, and a second set of wheels 36 configured to engage rails extending in a second direction perpendicular to the first direction. At least one of the sets of wheels 34, 36 is vertically movable relative to the vehicle body 32 to permit selective engagement with the respective rails. The load handling device 30 further comprises lifting tethers 38 and a grabber device 39 suspended from the vehicle body 32. As illustrated in Figures 4(a) and 4(b), the vehicle body 32 defines a container receiving space 41 dimensioned to receive a storage container 12 when lifted. The lifting tethers 38 are wound onto a reel driven by a winch mechanism within the vehicle body 32 to control vertical movement of the grabber device 39.

[0040] As illustrated in Figure 5, the grabber device 39 comprises a lifting frame and a plurality of gripper elements 40 movable between a contracted position and an expanded position. In the contracted position, the gripper elements 40 are insertable into openings 40b formed in a rim of the storage container 12. The spatial distribution of the gripper elements 40 corresponds to the distribution of openings 40b in the rim of the storagecontainer 12. Actuation of the gripper elements 40 from the contracted position to the expanded position causes engagement beneath the rim, thereby securing the storage container 12 to the grabber device 39. Retraction of the lifting tethers 38 then lifts the storage container 12 into the container receiving space 41, as shown in Figure 4(a), thereby enabling lateral transport across the grid framework structure 14. When the storage container 12 is to be deposited, the lifting tethers 38 are extended to lower the storage container 12 into a target position, and the gripper elements 40 are returned to the contracted position to disengage from the openings 40b.

[0041] Under the control of the control system, one or more load handling devices operating on the track system can be instructed to retrieve storage containers 12 from the buffer (i.e., grid framework structure) and deliver the storage containers to a pallet transfer station 50 shown in Figure 6. The pallet transfer station 50 comprises a de-palletising station 52 and a consolidation station 54. At the de-palletising station 52, case units 44 are removed from incoming pallets 46 and transferred into storage containers 12 for storage within the buffer 24. In contrast, at the consolidation station 54, storage containers 12 loaded with one or more case units retrieved from the buffer 24 are transferred onto pallets 46 for onward transport. A robotic material handling system for performing de-palletising and / or palletising operations is provided at the pallet transfer station 50. The robotic material handling system comprises a robotic arm 66 having an end effector 68 configured to engage with storage containers 12 and with slip sheets 56 used in pallet formation. The robotic material handling system further comprises a vision system and a control system comprising one or more processors and memory storing instructions. When executed, the instructions cause the robotic arm 66 to orient and position storage containers 12 and slip sheets 56 based on positional and orientation information detected by the vision system.

[0042] Figure 7 illustrates storage containers 12 arranged in multiple layers on a pallet 46, with slip sheets 56 interposed between successive layers. During transport of the pallet loaded with storage containers, relative displacement between layers may occur due to vibration, acceleration or uneven ground. The slip sheet 56 reduces such relative movement and stabilises the stacked configuration by maintaining the relative positions of storage containers 12 in adjacent layers.As illustrated in Figures 8(a) and 8(b), the slip sheet 56 comprises a plurality of seats 58 arranged in a predetermined pattern that is rotationally symmetrical about the geometric centre of the slip sheet 56. The pattern of seats 58 corresponds to the arrangement of storage containers 12 within each layer of the stack. In the example shown in Figure 8, the pattern exhibits four-fold rotational symmetry, with four seats arranged such that two of the seats are oriented in a first direction and the other two are oriented in a second direction different from the first. This arrangement accommodates storage containers 12 having a rectangular footprint and permits efficient use of the available surface area of the slip sheet 56 while maintaining balance and stability of the stack.

[0043] Each seat 58 comprises a recess or depression having a footprint that substantially corresponds to the footprint of a storage container 12, thereby allowing the base of each container 12 to be securely seated within the respective depression. The depressions extend downwardly from an upper surface of the slip sheet 56 and are dimensioned to receive the base or bottom wall of the storage container 12. When the slip sheet 56 is positioned between layers, the depressions extend at least partially into the open mouths of the storage containers 12 located immediately beneath the slip sheet 56. In this way, the slip sheet 56 is effectively sandwiched between layers, with the storage containers 12 of an upper layer seated within the depressions and the depressions extending downwardly into the storage containers 12 of the lower layer. The engagement between the storage containers 12 and the seats 58 maintains the relative positions of the containers 12 in adjacent layers and thereby reduces or prevents inter-layer slippage.

[0044] The slip sheet 56 further comprises engagement features arranged in a spatial distribution that corresponds to the spatial distribution of the engagement features present on the storage containers 12, thereby enabling the same end effector 68 to engage with both the storage containers 12 and the slip sheet 56. This removes the need for different types of end effectors and simplifies the palletising operation. The engagement features may comprise depressions, openings or recesses distributed across the surface of the slip sheet 56 in a pattern that matches the pattern of engagement features on the storage containers 12.

[0045] In the example shown in Figures 8(a) and 8(b), the engagement features of the slip sheet 56 can be arranged in two sets, namely a first set of engagement features 60a and a secondset of engagement features 60b. The second set of engagement features 60b is oriented differently relative to the first set of engagement features 60a, corresponding to different orientations of the storage containers 12 within each layer. This arrangement allows the end effector 68 to engage the slip sheet 56 at different orientations without requiring the robotic arm 66 to change its axis of approach. By having engagement features at different orientations, the need to reorient the robotic arm 66 between different axes is reduced, thereby increasing the speed and efficiency with which the robotic arm 66 can pick up and position the slip sheet 56.

[0046] The slip sheet 56, 56b comprises a marker 62, 62b that can be positioned at or near or adjacent the geometric centre of the slip sheet 56, 56b. The marker 62, 62b has a shape exhibiting rotational symmetry that corresponds to the pattern of symmetry of the plurality of seats 58 and shares the same rotational axis as the pattern of seats 58. The marker 62, 62b is shaped with orientation features that enable the vision system to determine the orientation of the slip sheet 56, 56b and, consequently, the spatial distribution of the seats 58 and the engagement features 60a, 60b. The marker 62, 62b acts as a reference point for determining the position and / or orientation of the plurality of seats 58 and for determining a positional relationship between the marker 62, 62b and the engagement features 60a, 60b of the slip sheet 56, 56b. The control system may store predetermined spatial relationships between the marker 62, 62b and the seats 58, and between the marker 62, 62b and the engagement features 60a, 60b, such that, once the vision system detects the marker 62, 62b and determines its position and orientation, the control system can infer the corresponding positions and orientations of the seats 58 and the engagement features 60a, 60b relative to a reference frame. By detecting the orientation of the marker 62, 62b, the vision system can provide instructions to the robotic arm 66 to correctly position the end effector 68 relative to one of the engagement features 60a, 60b, thereby enabling accurate engagement and placement of the slip sheet 56, 56b on a layer of storage containers 12.

[0047] The orientation and position of the marker 62, 62b may correspond with the spatial distribution of the engagement features 60a, 60b of the slip sheet 56, 56b, allowing the vision system to determine the position and orientation of the engagement features from the orientation of the marker 62, 62b alone. Similarly, the orientation and position of themarker 62, 62b may correspond with the spatial distribution of engagement features of each of the storage containers 12 seated on the slip sheet 56, 56b, enabling the vision system to instruct the robotic arm 66 to pick up one or more storage containers 12 from the slip sheet 56, 56b based on the detected orientation of the marker 62, 62b and to align the seats 58 with intended locations for receiving storage containers 12.Figures 9(a) and 9(b) illustrate a perspective view of the robotic arm 66 comprising the end effector 68 configured to engage with the slip sheet 56 and the storage containers 12 described with reference to Figure 7. To provide manoeuvrability of the end effector 68 for picking up the slip sheet 56 and placing it on the pallet 46 such that straight edges of the slip sheet 56 align with straight edges of the pallet 46, the robotic arm 66 may be a six-axis robotic arm having six independently moveable joints, giving six degrees of freedom. Each of the independently moveable joints may be driven by separate motors or by connections to one or more motors via belts or gears.

[0048] The present disclosure is not limited to a six-axis robot. The number of joints that are independently moveable can range from three to six axes. For example, the robotic arm 66 may be a SC ARA robot having four axes of independent joint movement, or another articulated configuration providing between three and six degrees of freedom. The selection of the number of axes depends on the required workspace, pay load capacity and precision of alignment between the slip sheet 56 and the pallet 46.

[0049] Figure 9(a) shows engagement of the end effector 68 with engagement features of the slip sheet 56. The example of the robotic arm 66 shown in Figure 9(a) is a six-axis robot. The second set of engagement features is visible in Figure 9(b). As discussed with reference to Figure 8, the second set of engagement features reduces travel distance of the end effector 68 when aligning itself with engagement features of the slip sheet 56. One or more motors of the robotic arm 66 may exhibit slower response when aligning the end effector 68 with the slip sheet 56, and providing more than one set of engagement features reduces the movement and thus the time to align the end effector 68 with a set of engagement features.

[0050] The end effector 68 comprises gripper elements configured to engage with the engagement features of the slip sheet 56 in a manner analogous to engagement with the storagecontainers 12. The gripper elements are moveable from a contracted position to be received in the engagement features to an expanded position to engage with the slip sheet 56. The spacing between the gripper elements of the end effector 68 corresponds to the spacing between the engagement features of the slip sheet 56 and the engagement features of the storage containers 12, thereby allowing the same end effector 68 to handle both the slip sheet 56 and the storage containers 12 without requiring different types of end effectors.

[0051] The robotic arm 66 is controlled by the control system which receives signals from the vision system. The vision system detects the marker 62 on the slip sheet 56 to determine the position and orientation of the slip sheet 56. The control system uses this information to generate instructions for the robotic arm 66 to position the end effector 68 such that gripper elements align with one of the sets of engagement features 60a, 60b on the slip sheet 56. Once aligned, the gripper elements engage with the engagement features and the robotic arm 66 lifts the slip sheet 56 for placement on the pallet 46 or on a layer of storage containers 12 already arranged on the pallet 46.

[0052] The robotic arm 66 may be mounted on a fixed base or on a movable platform to extend its operational range across multiple pallets or conveyor lines. The control system may employ sensor feedback from cameras, encoders or proximity sensors to dynamically adjust position and orientation of the end effector 68 in real time during engagement with the slip sheet 56 or the storage containers 12. This feedback allows the robotic arm 66 to compensate for variations in positioning or geometry of the slip sheet 56 or the storage containers 12.

[0053] In alternative examples, the end effector 68 may incorporate engagement mechanisms such as vacuum grippers, magnetic couplers, mechanical clamps or hybrid gripping systems combining suction and mechanical retention. The engagement interface between the end effector 68 and the slip sheet 56 may include adaptive features such as compliant fingers or self-aligning jaws to accommodate variations in positioning or geometry of the slip sheet 56.The disclosed configuration is applicable to automated de-palletising operations in which the robotic arm 66 removes slip sheets 56 and storage containers 12 sequentially from a stacked arrangement. The robotic arm 66 maintains alignment and stability throughout the process by using the vision system to detect the marker 62 on the slip sheet 56 and determine position and orientation of the slip sheet 56 and the storage containers 12 seated on the slip sheet 56. The control system generates instructions for the robotic arm 66 to position the end effector 68 to engage with engagement features of the slip sheet 56 or the storage containers 12, thereby enabling controlled removal from the pallet 46.

[0054] Also shown in Figures 8(a) and 8(b), the slip sheet 56 comprises a peripheral wall 64 extending downwardly from the top surface and extending around the periphery of the slip sheet. These downwardly extending walls 64 allow multiple slip sheets to be stacked vertically without contacting or deforming the seats 58. The slip sheet shown in comprises an upper surface bounded by a peripheral rim 67 extending around the outer edge of the slip sheet, the rim 67 forming an upwardly projecting marginal lip. The peripheral wall extends downwardly from the rim along the outer periphery of the slip sheet.

[0055] For automated handling, the slip sheets are configured to be stacked one on top of another such that a robotic arm 66 with an end effector 68 can engage with a single slip sheet 56 positioned at the top of the stack and separate it from the slip sheet immediately below. For reliable singulation, it is desirable that adjacent slip sheets in the stack do not mechanically interlock or otherwise engage with one another.

[0056] However, the peripheral downwardly extending walls 64 may have a tendency to contact and engage with corresponding walls of an adjacent slip sheet in the stack, which can result in adjacent slip sheets adhering or sticking together. This may cause the robotic arm to inadvertently lift more than one slip sheet when attempting to pick up a single slip sheet.

[0057] To mitigate this issue and facilitate reliable separation, the slip sheet comprises one or more separator elements 69 extending downwardly from the underside of the top wall of the slip sheet. As illustrated in Figure 13, each separator element 69 is configured to abut or seat against an upper surface of the slip sheet immediately below in the stack. Theseparator elements thereby maintain a controlled spacing between adjacent slip sheets and reduce the likelihood of engagement between the peripheral walls of adjacent sheets.

[0058] In the illustrated embodiment, the separator elements are formed as protruding features extending downwardly from the underside of the slip sheet. One or more such separator elements are positioned at locations susceptible to inter-engagement between adjacent sheets. In the example shown in Figure 13, the separator elements 69 are positioned around the periphery of the slip sheet so as not to interfere with the depressions forming the seats 58. In particular, separator elements may be positioned at or adjacent the comers of the slip sheet.

[0059] When stacked, the separator elements 69 contact the upper surface of the slip sheet immediately below, thereby limiting inter-engagement between adjacent sheets and enabling a single slip sheet to be readily separated by the robotic arm.

[0060] Figures 10(a) and 10(b) relate to the features shown in Figures 9(a) and 9(b) and illustrate perspective views of an end effector 68. Figure 10(a) provides an isometric view of the end effector 68 and Figure 10(b) shows a perspective view of the underside of the end effector 68. The end effector 68 comprises a plurality of gripper elements 40b configured to selectively engage with either storage containers 12 or a slip sheet 56. The spatial distribution of the gripper elements 40b corresponds to the spatial distribution of the gripper elements 40 of the grabber device 39 described with reference to Figure 5. This correspondence ensures compatibility between the end effector 68 and both components, allowing the same gripping arrangement to be used to pick up and manipulate the storage containers 12 and the slip sheet 56 without requiring reconfiguration or tooling changes.

[0061] Each gripper element 40b is moveable between a contracted position and an expanded position. In the contracted position, the gripper elements 40b are received within engagement features of the slip sheet 56 or storage containers 12. In the expanded position, the gripper elements 40b engage with the engagement features to secure the slip sheet 56 or storage containers 12 for lifting and manipulation by the robotic arm 66. The gripper elements 40b may be actuated by electric, pneumatic or hydraulic actuators mounted within the end effector 68 and may be controlled independently or in grouped sets. Thegripper elements 40b may include resilient or compliant gripping members configured to deform when inserted into an engagement feature, thereby accommodating variation while providing secure retention.

[0062] In alternative examples, the gripper elements 40b may comprise mechanical finger or jaw elements, resilient or compliant gripping members, magnetic coupling elements for engaging ferromagnetic regions of a slip sheet or container, or hybrid gripping systems combining mechanical retention with vacuum suction or adhesive pads. The number, arrangement and spacing of the gripper elements 40b may vary depending on the shape or configuration of the slip sheet 56 or the storage containers 12. The end effector 68 may include adjustable or telescopic gripper elements to alter spacing or reach, and may include self-aligning or compliant joints to accommodate minor positional or angular misalignments during engagement. The gripper elements 40b may also include integrated sensors, such as force sensors, proximity sensors or encoders, to detect secure engagement or provide feedback to the control system.

[0063] Figure 11 illustrates a top plan view of the slip sheet 56 showing the plurality of seats 58 arranged in a pattern with rotational symmetry about the marker 62 disposed substantially at the geometric centre of the slip sheet 56. Figure 11 systematically shows the position of the robotic arm 66 in relation to the slip sheet 56. In the example shown, the plurality of seats 58 comprises four seats 58, each seat 58 having a footprint that substantially corresponds to the footprint of the base of a storage container 12, or is slightly larger than the base of the storage container 12, to ensure that the storage container 12 is properly seated. Two of the seats 58 are oriented in a lengthwise direction and the other two seats 58 are oriented in a crosswise direction, thereby providing a pinwheel arrangement for rectangular storage containers 12. The slip sheet 56 shown is substantially square in shape with sides of equal length, and the arrangement of the seats 58 provides efficient utilisation of surface area.

[0064] Figure 11 further illustrates an example in which the marker 62 has rotational symmetry coinciding with axes of rotational symmetry of the pattern of seats 58. The marker 62 comprises one or more orientation elements formed by geometric features or contours that are detectable by the vision system when the slip sheet 56 is viewed from above. Theorientation elements may be defined by edges, arms, recesses, raised portions, vertices, surface contours, printed patterns or contrasting regions that provide sufficient visual distinction for detection by image acquisition sensors. The marker 62 may be cross-shaped or cruciform. The pattern of seats 58, and thus the spatial distribution of the seats 58 relative to the marker 62, is predetermined and stored in memory of the control system. The x and y distances between each seat 58 and the marker 62 may be predetermined, and the angular orientation of each seat 58 relative to the marker 62 may also be predetermined. The orientation and position of the marker 62 therefore provide an indication of the orientation and position of each seat 58. There is no inherent limitation on the sequence in which the robotic arm 66 places storage containers 12 onto the slip sheet 56. A loading sequence may be selected to reduce the likelihood of obstructions caused by previously placed storage containers and to provide an unobstructed approach to an empty seat. Accordingly, with reference to numbering of seats shown in Figure 11, a loading sequence may follow the order 4, 3, 2 and 1, and during unloading the sequence may be reversed.

[0065] The geometric features of the marker may be indicative of the orientation of the slip sheet 56. This is useful where the slip sheet 56 is not square. For a cross-shaped contour, one orientation element can be longer than another orientation element to provide directionality. A longer orientation element may indicate the Y-axis of a Cartesian coordinate system and the shorter orientation element may indicate the X-axis, as shown in Figure 12. In the example shown in Figure 11 , orientation elements along the X-axis and Y -axis may be equal in length such that the rotational symmetry of the marker 62 coincides with the rotational symmetry of the pattern of seats 58 about the geometric centre of the slip sheet 56. The orientation elements of the marker 62 may also coincide with positioning and orientation of engagement features of the slip sheet 56.

[0066] The orientation elements may comprise elongate arms extending along respective axes, the relative lengths, widths or shapes of the arms defining distinguishable geometric contours. Figure 12 relates to the features shown in Figures 7 to 11 and illustrates a top plan view of a second example of a slip sheet 56b. In this example, the slip sheet 56b comprises a marker 62b exhibiting a different order of rotational symmetry compared to the pattern of seats 58. The marker 62b has a cruciform or cross-shaped configuration in which anorientation element extending along the Y-axis is longer than an orientation element extending along the X-axis. This asymmetry imparts a two-fold rotational symmetry to the marker 62b. In contrast, the pattern of seats 58 arranged on the slip sheet 56b exhibits four-fold rotational symmetry about the geometric centre of the slip sheet 56b. Both the marker 62b and the pattern of seats 58 share the same rotational axis, which passes through the geometric centre of the slip sheet 56b.

[0067] The slip sheet 56b comprises four seats 58 arranged in a pattern exhibiting four-fold rotational symmetry. Each seat 58 is configured to receive and locate a storage container 12, and the seats 58 are positioned such that the pattern is rotationally symmetrical about the centre at intervals of ninety degrees. The arrangement enables efficient use of available surface area and maintains balance and stability of the stacked configuration. The marker 62b is positioned at or near the geometric centre and comprises orientation features enabling a vision system to determine the orientation of the slip sheet 56b. The cruciform shape includes a first arm extending along the Y-axis and a second arm extending along the X-axis, the first arm being longer than the second arm. The difference in arm lengths breaks four-fold symmetry and imparts two-fold rotational symmetry, enabling the vision system to distinguish different rotational positions and determine orientation with precision, particularly when the slip sheet 56b has a rectangular or square footprint.

[0068] The rotational symmetry of the marker 62b is a factor of the rotational symmetry of the pattern of seats 58. In the example shown in Figure 12, the marker 62b exhibits two-fold rotational symmetry, while the pattern of seats 58 exhibits four-fold rotational symmetry, such that the rotational symmetry of the seat pattern is a multiple of the rotational symmetry of the marker 62b. The provision of a marker 62b having a lower order of rotational symmetry than the pattern of seats 58 allows the vision system to determine the orientation of the slip sheet 56b unambiguously by detecting the marker 62b. The asymmetry of the marker 62b ensures that the vision system can distinguish between different rotational positions even when the pattern of seats 58 exhibits higher-order rotational symmetry, thereby enabling the control system to generate accurate positioning instructions for the robotic arm 66 and reducing the risk of misalignment.In operation, the vision system determines the orientation and positioning of the slip sheet 56 or 56b from the orientation and position of the marker 62 or 62b. The vision system detects the marker and transmits one or more signals to the control system. The control system uses predetermined spatial relationships between the marker and the plurality of seats 58, and optionally between the marker and the engagement features 60a, 60b, to calculate coordinates and angular orientations for seat locations and engagement locations. The control system then generates instructions for the robotic arm 66 to position the end effector 68 such that it can engage the slip sheet 56 or place a storage container 12 into a specific seat 58. The vision system may comprise one or more cameras mounted above the pallet 46 or attached to the robotic arm 66, and image processing may be used to identify the marker and determine its position and orientation. The control system may adjust the position and orientation of the end effector 68 in real time to compensate for positional variations of the slip sheet 56.

[0069] The marker may comprise other geometric features, including asymmetric shapes, barcodes, fiducial markers or patterns of contrasting colours detectable by the vision system. The marker may be printed, embossed, engraved or otherwise applied to a surface of the slip sheet. The control system may store multiple predetermined spatial relationships corresponding to different slip sheets or different seat configurations, allowing the robotic arm 66 to handle a variety of slip sheet designs without manual reconfiguration. The slip sheet 56, 56b may be fabricated as a unitary structure, for example as a single-piece component formed from a polymeric material. The slip sheet 56, 56b may be manufactured by moulding processes such as injection moulding, thermoforming, vacuum forming or blow moulding, depending on required structural rigidity, thickness and production volume. In such embodiments, the plurality of seats 58, the engagement features 60a, 60b and the marker 62, 62b may be formed integrally during the moulding process as recessed, raised or contoured regions of the slip sheet 56, 56b. The polymeric material may comprise high-density polyethylene, polypropylene, reinforced thermoplastics or other loadbearing plastics selected to provide sufficient stiffness, impact resistance and dimensional stability under repeated handling. In alternative embodiments, the slip sheet 56, 56b may be formed from composite materials, fibre-reinforced plastics, metal sheet material or reinforced fibreboard, provided that sufficient rigidity is achieved to maintain seatgeometry under load. The slip sheet 56, 56b may further include integrally moulded reinforcement ribs, stiffening structures or peripheral edge formations to enhance load-bearing capacity and resist bending when positioned between layers of storage containers 12. Surface textures, friction-enhancing regions or resilient inserts may optionally be incorporated in or around the seats 58 to increase resistance to slippage. The geometric features or contours of the orientation elements may be formed integrally with the slip sheet 56, 56b, for example as moulded raised or recessed structures, or may be applied to a surface of the slip sheet 56, 56b by printing, embossing, engraving or contrasting colour application.

[0070] Accordingly, a palletised assembly may comprise a pallet 46, a first layer of storage containers 12 disposed on the pallet 46, a slip sheet 56 disposed on the first layer, and a second layer of storage containers 12 disposed on the slip sheet 56 with the storage containers 12 seated in the plurality of seats 58. The slip sheet 56 reduces slippage between adjacent layers and maintains defined positioning of storage containers 12 through engagement between the seats 58 and container bases and through partial extension of depressions into the open mouths of the storage containers 12 below. The robotic material handling system comprising the robotic arm 66, the end effector 68, the vision system and the control system enables automated palletising and de-palletising by detecting the marker 62, determining slip sheet orientation and positioning, selecting engagement features 60a, 60b and aligning the end effector 68 for engagement, thereby enabling accurate placement of slip sheets 56 and storage containers 12 without requiring tool changes.

[0071] Accordingly, while the seats are described with reference to the container shown in the figures, the seats may be adapted to accommodate containers of differing shapes, dimensions, and structural configurations without departing from the scope of the present disclosure.

Claims

Claims1. A slip sheet for placement between layers of storage containers on a pallet to prevent relative slippage between the layers, the slip sheet comprising:a plurality of seats, each seat being shaped and sized to accommodate a respective storage container;the plurality of seats being arranged in a pattern that is rotationally symmetrical about a centre of the slip sheet;a plurality of engagement features configured to enable a robotic end effector to engage with and lift the slip sheet,a marker having a rotational symmetry that is a factor of the rotational symmetry of the pattern of seats and which shares the same rotational axis, the marker comprising orientation elements detectable by a vision system for determining the rotational orientation of the slip sheet and thereby, the orientation of the plurality of seats.

2. The slip sheet of claim 1, wherein the marker comprises one or more geometric features or contours forming said orientation elements that are detectable by a machine vision system when viewed from above.

3. The slip sheet of Claim 1 or 2, wherein the marker is disposed substantially at the geometric centre of the slip sheet so as to align with the rotational symmetry axis of the slip sheet.

4. The slip sheet of any preceding claim, wherein the marker defines a cross-shaped or cruciform pattern having an axis of rotational symmetry aligned with the axis of rotational symmetry of the plurality of seats.

5. The slip sheet of any preceding claim, wherein each seat comprises a depression bounded by peripheral walls configured to locate and laterally restrain a storage container.

6. The slip sheet of claim 5, further comprising one or more separator elements extending downwardly from an underside of the slip sheet and configured to abut an upper surfaceof an adjacent slip sheet when stacked, thereby maintaining spacing between stacked slip sheets and reducing engagement between the peripheral walls of adjacent slip sheets.

7. The slip sheet of any preceding claim, wherein the plurality of seats comprises four seats disposed around the centre of the slip sheet such that the pattern of seats has a four-fold rotational symmetry pattern.

8. The slip sheet of claim 7, wherein the marker has a two-fold rotational symmetry.

9. The slip sheet of claim 7 or 8, wherein one or more of the four seats is oriented differently around the centre of the slip sheet to enable nesting of four storage containers on the slip sheet.

10. The slip sheet of claim 9, wherein the one or more of the four seats are oriented along a first direction and others of the one or more of the four seats are oriented along a second direction substantially perpendicular to the first direction.

11. The slip sheet of any preceding claim, wherein the engagement features comprise apertures, recesses, or projections configured to mate with corresponding gripping or vacuum features of the end effector.

12. The slip sheet of any preceding claim, wherein the plurality of engagement features are configured to engage with the same robotic end effector used to handle the storage containers.

13. The slip sheet of any preceding claim, wherein the orientation of the marker coincides with the spatial distribution of the plurality of engagement features.

14. The slip sheet of any preceding claim, wherein the plurality of engagement features comprises a first set of engagement features and a second set of engagement features, the first set of engagement features being oriented differently to the second set of engagement features such that, in use, the robotic end effector is oriented differentlywhen engaging with the first set of engagement features to when engaging the second set of engagement features.

15. The slip sheet of any of preceding claim, wherein the rotational symmetry of the marker coincides with the rotational symmetry of the pattern of seats.

16. The slip sheet of any preceding claim, wherein the slip sheet is moulded as a single piece of polymeric material.

17. A palletised assembly comprising:a pallet;a first layer of storage containers disposed on the pallet;a slip sheet according to any of the claims 1 to 16 disposed on the first layer; and a second layer of storage containers disposed on the slip sheet in the plurality of seats.

18. A robotic material handling system comprising:a robotic end effector configured to engage with storage containers;a vision system configured to detect the orientation of a slip sheet according to any of claims 1 to 16; andcontrol system comprising one or more processors and memory storing instructions that when executed by the one or more processors cause the one or more processors to orient and position the slip sheet and / or storage containers based on the detected orientation of the marker.

19. The system of claim 18, wherein the robotic end effector is configured to engage with both the storage containers and the slip sheet using a common engagement mechanism.

20. A method of positioning a slip sheet of any of the claims 1 to 16 between layers of storage containers on a pallet, comprising:detecting a marker on the slip sheet using a vision system;determining an orientation of the slip sheet based on the detected marker;gripping the slip sheet using a robotic end effector that engages with the plurality of engagement features on the slip sheet; andplacing the slip sheet onto a layer of storage containers such that the plurality of seats on the slip sheet are aligned with the storage containers below.

21. The method of claim 20, further comprising placing a subsequent layer of storage containers into the plurality of seats of the slip sheet.

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