Load handling devices and sortation systems

Abstract

A load handling device 110, such as an automated guided vehicle, comprising a body mounted with movement means such as wheels and an item-carrying tray 114 rotatably mounted to the body by support arm

Description

The disclosure herein relates to load handling devices for use in sortation systems and sortation systems comprising such load handling devices. In particular, the disclosure relates to sortation systems comprising a plurality of destination containers and load handling devices for depositing items into the destination containers. Background Distribution and fulfilment operations typically involve retrieving one or more items (that make up the order) from a warehouse or storage facility, consolidating those items into a single order and dispatching the order to a customer. In order to improve the efficiency of fulfilment operations, most warehouses / fulfilment centres make use of significant automation throughout the process. For example, many systems use at least some automation when retrieving items from storage. In addition, many systems then also use at least some automation when sorting and / or consolidating retrieved items into orders. For example, automated sortation often involves using robotic load handling devices, such as automated guided vehicles (AGV) or autonomous mobile robots (AMR), to collect an item to be sorted from a pick-up point and to deliver the item to an appropriate destination, such as to an order consolidation container etc. Examples of robotic load handling devices that are used in sortation systems are described in WO2018175910A1 and WO2020117874A1. WO2018175910A1 describes systems for automatically sorting objects in which automated carriers are used to deliver objects to an associated destination. In the embodiments shown in Figures 4 and 16 of WO2018175910A1, the automated carriers comprise a bomb-bay door that opens in order to drop an object from the carrier. Figure 24 then shows an alternative embodiment of the automated carrier in which the carrier has a conveyor that is actuable to move a bin or box on the carrier in either of two opposing directions in order to deposit an object from the carrier. Figure 27 of then shows a further alternative embodiment of the automated carrier in which the carrier includes a tilt tray that is actuable to tip an object from the carrier. WO2020117874A1 then describes robotic vehicles for delivering articles to a destination in, for example, an order processing facility. According to WO2020117874A1, the robotic vehicles comprise a tilt tray having a first section and a second section that can each tilt independently in order to separately deposit articles carried on the first and second sections. In the embodiment shown in Figure 1 of WO2020117874A1 the first and second sections tilt in opposite directions, whereas in the embodiment shown in Figure 5 of WO2020117874A1 the first and second sections tilt in the same direction. WO2020117874A1 also describes how each section of the tilt tray may have a conveyor for conveying articles down the tilt tray. Whilst these may be suitable for automatically sorting robust items and parcels, they risk damaging more fragile items when the items fall from the carrier or vehicle. They are also incapable of 5 ensuring that items are deposited into specific areas of a destination as items are likely to roll and / or bounce after falling from the carrier or vehicle. Summary of the invention According to a first aspect, there is provided a load handling device comprising a body mounted on movement means, and a tray arranged to carry one or more items, the tray being mounted to the body by one or more support arms, and the one or more support arms being arranged to move the tray between a retracted position and an extended position. In the retracted position the tray is disposed at least partially within a footprint of the body and in the extended position the tray is disposed away from the body. The load handling device is arranged to allow the tray to be tipped when extended beyond the retracted position. The tray may be rotationally mounted to the one or more support arms in order to allow the tray to tip. The load handling device may be arranged to tip the tray from a carry position towards a tipped end position. The load handling device may be arranged to tip the tray between a first tipped end position and a second tipped end position, wherein the carry position is between the first tipped end position and the second tipped end position. The load handling device may be arranged to tip the tray away from the carry position. The carry position may be substantially horizontal. The load handling device may further comprise a backstop mounted to the body and located immediately behind the tray when in the retracted position. The backstop may be arranged to prevent items from falling off the tray when in the retracted position. The carry position may be any of (i) substantially horizontal and (ii) tipped towards the backstop when in the retracted position. The load handling device may further comprise a tipping mechanism arranged to tip the tray. The tipping mechanism may comprises a motor, a telescopic drive shaft and a gear assembly, the motor being arranged to drive the telescopic drive shaft and the gear assembly being arranged to translate rotation of the telescopic drive shaft into rotation of the tray. Preferably, the motor remains within the footprint of the body and the telescopic drive shaft is arranged to extend and retract with the tray. The load handling device may be arranged to move the tray away from the tipped end position to the carry position when moving away from the extended position towards the retracted position. The load handling device may be arranged to ensure that the tray is in the carry position when in the retracted position. The load handling device may be arranged to allow the tray to be lowered and tipped when extended beyond the retracted position. The load handling device may be arranged move the tray from an upper position towards a lower position when the tray is extended beyond the retracted position. The load handling device may be arranged to only move the tray away from the upper position when extended beyond the retracted position. The load handling device may be arranged to move the tray away from the lower position to the upper position when moving from the extended position to the retracted position. The load handling device may be arranged to ensure that the tray is in the upper position when in the retracted position. The load handling device may be arranged to tilt the one or more support arms in order to lower the tray when extended beyond the retracted position. Each of the one or more support arms may be pivotally mounted to the body in order to allow the support arm to tilt relative to the body and thereby move the tray between the upper position and the lower position. Each of the one or more support arms may be pivotally mounted to the body in order to allow the support arm to tilt thereby adjusting the vertical position of the distal end of the support arm and the tray mounted thereto. It will be appreciated that the load handling device may be arranged to tilt the one or more support arms to elevate the tray when extended beyond the retracted position. The load handling device may further comprise a tilting mechanism that is configured to control the angular position of each of the one or more support arms relative to the body. The tilting mechanism may comprise one or more linear actuators, each of the one or more linear actuators being pivotally mounted between the body and the one or more of the support arms. Each of the one or more linear actuators may be pivotally mounted between the body and a proximal end of one or more of the support arms, the proximal end of each of the one or more support arms being opposite to a distal end to which the tray is mounted.Each of the one or more support arms may be extendable in order to allow the tray to move between the retracted position and the extended position. Each of the one or more support arms may comprise a base section mounted to the body and an extending end section movably mounted to the base section, the tray being mounted to the extending end section. The load handling device may further comprise a stabilising mechanism mounted to the body, the stabilising mechanism comprising one or more engagement devices arranged to engage cooperating features providing on one or more of (i) a surface on which the load handling device operates and (ii) a destination container. The load handling device may be arranged to stabilise the load handling device when the tray is beyond the footprint of the body. Each of the one or more engagement devices may be arranged to engage with a destination container located immediately adjacent to the load handling device. A destination container is a container into which the load handling device is depositing an item from the tray. Each of the one or more engagement devices may be parallel with the one or more supports arm and extend away from the body of the load handling device. According to a second aspect, there is provided a sortation system comprising a sortation surface, a plurality of destination containers disposed adjacent to the sortation surface and a plurality of load handling devices according to the first aspect. The plurality of load handling devices are arranged to travel on the sortation surface and to deposit items into the destination containers. According to a third aspect, there is provided a method of operating a load handling device in order to deposit an item into a destination container. The method comprises receiving the item in a tray of the load handling device, travelling across a sortation surface to a drop-off point adjacent to the destination container, moving the tray from a retracted position towards an extended position such that the tray is disposed over the destination container, and rotating the tray from a carry position towards a tipped end position such that the item is tipped from the tray into the destination container. The method may further comprise, after tipping the item from the tray, rotating the tray back towards the carry position, and moving the tray back towards the retracted position. The method may further comprise, after moving the tray from a retracted position towards an extended position, lowering the tray from an upper position towards a lower position or raising the tray from an upper position towards an elevated position by tilting the support arms. The method may then further comprise, after tipping the item from the tray, respectively raising or lowering the tray back towards the upper position. The method may further comprise, prior to receiving the item in a tray of the load handling device, travelling across the sortation surface to a pick-up point at which the item is deposited on to the tray. Other variations and advantages will become apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS 10 1224 These and other aspects of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of an example of a sortation system as described herein; 5 Figures 2a to 2d illustrate of an example of a load handling device suitable for use in the system of Figure 1; Figures 3a to 3f are a sequence showing the load handling device of Figures 2a to 2d operating to deposit an item in a destination container; Figure 4 illustrates the load handling device of Figures 2a to 2d in a possible mode of operation; 10 Figure 5 illustrates the load handling device of Figures 2a to 2d in another possible mode of operation; Figures 6a and 6b illustrate an example of a support arm, extension mechanism and tipping mechanism suitable for use with the load handling device of Figures 2a to 2d; Figure 7 illustrates an alternative example of a load handling device suitable for use in the system of 15 Figure 1; Figure 8 illustrates an example of a stabilising mechanism of the load handling device of Figure 7; Figures 9a and 9b illustrate an embodiment of a load handing device with a conveyor tray; Figures 10a and 10b illustrate an embodiment of a load handing device with a trap door tray; and Detailed description 20 The following embodiments represent preferred examples of how the invention may be practiced, but they are not necessarily the only examples of how this could be achieved. These examples are described in sufficient detail to enable those skilled in the art to practice the invention. Other examples may be utilised and structural changes may be made without departing from the scope of the invention as defined in the appended claims. Moreover, direction references and any other 25 terms having an implied orientation are given by way of example to aid the reader's understanding of the particular examples described herein. They should not be read to be requirements or limitations, particularly as to the position, orientation, or use of the invention unless specifically set forth in the appended claims. Similarly, connection references (e.g., attached, coupled, connected, joined, secured, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other, unless specifically set forth in the appended claims. Similarly, wording such as "movement in the n-direction" and any comparable wording, where n is one of x, y or z, is intended to mean movement substantially along or parallel to the n-axis, in either direction (i.e., towards the positive end of the n-axis or towards the negative end of the n-axis). Figure 1 illustrates schematically an example of a sortation system 100, the sortation system 100 comprising a sortation surface 101, a plurality of destination containers 102 disposed adjacent to the sortation surface 101 and a plurality of load handling devices 110 arranged to travel on the sortation surface 101 and to deposit items into the destination containers 102. The sortation surface 101 comprises at least one supply zone 103 where the load handling devices 110 receive items (I) that are to be sorted. In the illustrated example, the supply zone 103 comprises an area on the sortation surface 101 into which the load handling devices 110 can travel and that defines one or more pickup points at which the load handling devices 110 can stop in order to receive items. For example, the supply zone 103 may be located adjacent to a pick station at which items are picked from a storage container (e.g. manually by a pick operative or automatically by a robotic pick device) or a conveyor and deposited on to a load handling device 110 for sortation. The system 100 then further comprises a plurality of destination zones 104 at which the destination containers 102 are located adjacent to the sortation surface 101. In the illustrated example, each destination zone 104 is provided by a bay or recess defined by the sortation surface 101, with each bay being arranged to receive a destination container 102. In particular, the sortation surface 101 is arranged such that the sortation surface 101 extends around the sides of the destination zones 104 whilst also providing an opening through which destination containers 102 can be moved into and out of the destination zone 104. The region of the sortation surface 101 immediately adjacent to a destination zone 104 therefore defines various drop-off points at which the load handling devices 110 can be positioned in order to deposit items into a destination container 102. This arrangement provides that the load handling devices 110 can access multiple sides (e.g. three out of four) of a destination container 102 located within a destination zone 104 and can therefore more easily deposit items into any and all areas of the destination container 102. The sortation surface 101 then provides a transit zone 105 that allows the plurality of load handling devices to travel between a supply zone 103 and each of the destination zones 104. In the illustrated example, the transit zone 105 comprises an area of the sortation surface 101 that provides sufficient space for multiple load handling devices 110 to operate simultaneously, travelling between any supply zones 103 and the destination zones 104. The sortation system 100 then further comprises a central control system 106 that is responsible for controlling and coordinating the movement and operation of the load handling devices 110 of the system 100. The central control system 106 therefore provides the instructions to the load handling devices 110. For example, these instructions may comprise, at least, information directing the load handling device 110 to a pickup point within the supply zone 103 (i.e. in order to collect item(s) to be sorted) and to a corresponding drop-off point adjacent to a target destination container 102. These instructions may also further comprise information directing the load handling device 110 on how to transport and deposit any item(s) being handled by the load handling device 100. The central control system 106 may therefore comprise any necessary components such as a memory, one or more processors, one or more transceivers for communicating with the load handling devices 110 and any other systems, and one or more sensors for monitoring the status of the sortation system 100. By way of example, the central control system 106 may comprise a computer vision system that allows the central control system 106 to monitor the locations, pose and load of the load handling devices 110. Figures 2a to 2d then illustrate an example of a load handling device 110 suitable for use with the sortation system 100 of Figure 1. In particular, the load handling device 110 of Figures 2a to 2d is arranged to be able to transport an item and carefully deposit the item into a destination container 102. The load handling device 110 is therefore arranged to move along the sortation surface 101 from where the load handling device 110 can receive an item at a pickup point within an induction zone 103 and deposit an item at a drop-off point immediately adjacent to a destination zone 104. Figures 3a to 3g then illustrate the load handling device 110 of Figures 2a to 2d in various different stages of operation. The load handling device 110 comprises a body 111 mounted on movement means 112, 113 that are arranged to allow the load handling device 110 to move around a surface beneath the load handling device 110. The load handling device 110 then further comprises a tray 114 arranged to carry one or more items, the tray 114 being mounted to the body by a pair of moveable support arms 115. In the example of Figures 2a to 2d, the movement means 112,113 comprises a pair of differentially driven wheels 112 located on opposite sides of the body 111, approximately halfway along the longitudinal (X) axis of the body 111, and a pair of caster wheels 113 located at opposite ends of the body 111 and aligned with the longitudinal (X) axis of the body 111. However, in an alternative example, the movement means may comprise one or more driven wheels and one or more steerable wheels. In a further alternative example, the movement means may comprise continuous tracks. The support arms 115 are arranged to move the tray 114 between a retracted position and an extended position. In the retracted position the majority of the tray 114 is disposed within a footprint of the body 111, as shown in Figure 2d, and in the extended position the tray 114 is disposed outside the footprint of the body 111. This arrangement provides that the tray 114 can be extended beyond the body 111 of the load handling device 110, such that the tray 114 can be positioned directly above the surface of an adjacent destination container 102. Then, when retracted so as to be at least mostly within the footprint of the body 111, any items carried by the tray 114 will also be within the footprint of the body 111, thereby ensuring that the centre of gravity remains within the footprint of the body 111, which in turn improves the stability of the load handling device 110 when moving. In the example of Figures 2a to 2d, the load handling device 110 is arranged such that, when the tray 114 is in the retracted position, the majority of the tray 114 is disposed above the body 111. However, in an alternative arrangement, the body 111 may comprise a cavity or recess that is arranged to receive the tray 114 when in the retracted position. In such an arrangement, at least a majority of the tray 114 may then be within the body 111 when in the retracted position. The load handling device may be arranged to move the tray 114 to any point between the retracted position and the extended position. In particular, the load handling device 110 may be instructed to move the tray 114 to anywhere between the retracted position and the extended position in dependence upon where within a target destination container 102 the item(s) on the tray 114 are to be deposited. By way of example, if it is desirable to deposit an item towards the middle of a destination container 102, then the load handling device 110 may be instructed to only extend the tray 114 to a partially extended position (i.e. rather than to fully extend the tray 114 to the extended position). In the example of Figures 2a to 2d, the load handling device 110 is arranged such that, when in the extended position, the tray 114 is disposed away from the body 111. In particular, the tray 114 is arranged to move in the longitudinal (X) direction (i.e. forwards and backwards) such that the tray 114 is disposed longitudinally away from the body 111 (e.g. with the tray 114 in front of the body 111), as shown in Figure 3b. However, in an alternative arrangement, the tray 114 may be arranged to move in the lateral (Y) direction (i.e. side to side) such that the tray 114 is disposed laterally away from the body 111 (i.e. with the tray 114 to one side of the body 111) when in the extended position. In the example of Figures 2a to 2d, the support arms 115 are extendable in order to allow the tray 114 to move between the retracted position and the extended position. In particular, as shown in Figures 3b to 3d, the support arms 115 are telescopic. Each of the support arms 115 is therefore provided by a telescopic linear rail that comprises a base section 115a mounted to the body 111, an extending intermediate section 115b movably mounted to the base section 115a, and an extending end section 115c movably mounted to the extending intermediate section 115b. The tray 114 is then mounted towards a distal end of the extending end section 115c. In an alternative arrangement, the telescopic support arms 115 may comprise just two sections (i.e. a base section and an extending end section directly mounted to the base section) or more than three sections (i.e. a base section, an extending end section and two or more extending intermediate sections mounted between the base section and the extending end section). The load handling device 110 then further comprises an extension mechanism 116 that is arranged to extend and retract the support arms 115. For example, the extension mechanism 116 may comprise one or more motorised pulleys, one or more linear actuators etc. The load handling device 110 is also arranged to allow the tray 114 to be lowered and tipped when extended beyond the retracted position. This arrangement provides that, when extended beyond the retracted position, the tray 114 can be lowered towards the surface of an adjacent destination container 102 and the tray 114 tipped such that any items carried on the tray 114 will slide gently off the tray 114 and onto a surface beneath the tray 114. In doing so, this arrangement provides that items can be carefully deposited onto a surface beyond the load handling device 110 without the items falling or dropping from a height. The load handling device 110 is therefore arranged to move the tray 114, when the tray 114 is extended beyond the retracted position, between a carry position and a tipped end position. In the carry position, the tray 114 is positioned such that any items carried on the tray 114 will remain on the tray 114. Consequently, when in the carry position the tray 114 may be substantially horizontal or level, as shown in Figures 3a and 3b. However, as will be described in more detail below, when in the carry position the tray 114 may be tipped towards a backstop 120 such that items on the tray 114 are supported between the tray 114 and the backstop 120. In a tipped end position, the tray 114 is then tipped such that any items carried on the tray 114 will be unloaded from the tray. Preferably, when in a tipped end position, the tray 114 is tipped such that the tray 114 is at angle (0) of 30 degrees or more below the horizontal. To ensure that items are reliably tipped from the tray 114, the load handling device 110 may be arranged such that, when in the tipped end position, the tray 114 is at angle (0) of at least 90 degrees below the horizontal (i.e. such that the tray 114 is perpendicular to the sortation surface 101). In any case, the load handling device 110 may be arranged to tip the tray 114 to any angle between a carry position and a tipped end position. In particular, the load handling device 110 may be instructed to tip the tray 114 to anywhere between a carry position and a tipped end position in dependence upon the nature of the items being deposited. By way of example, for an item that will easily roll from the tray 114, the load handling device 110 may be instructed to tip the tray 114 to an angle of between 30 and 45 degrees, whereas for an item that is harder to tip off, such as a heavy bag, the load handling device 110 may be instructed to tip the tray 114 to an angle of 90 degrees so as to ensure that the item will not remain on the tray 114 after being tipped. This approach of adapting the tipping angle used when depositing an item can save time by optimising the extent to which the tray 114 needs to be tipped for each deposition operation. The tray 114 is rotationally mounted to the support arms 115 in order to allow the tray 114 to tip. Specifically, the tray 114 is mounted to the support arms 115 by a tipping mechanism 117 that is configured to control the rotational position of the tray 114 relative to the support arms 115. The tipping mechanism 117 is therefore configured to rotate the tray 114 around a tipping axis in both a first rotational direction (Ri) and an opposite, second rotational direction (Rj), with the tipping axis being perpendicular to the extension and retraction of the tray 114. In the example of Figure 2, the tipping axis is parallel to the transverse (Y) direction and perpendicular to the longitudinal (X) direction. When rotated in the first rotational direction (Ri), a distal edge of tray 114 is lowered and an opposing proximal edge is raised, wherein the distal edge is that which is furthest from the body 111 when the tray 114 is extended and the proximal edge is that which is closest to the body 111 when the tray 114 is extended. When rotated in the second rotational direction (R2), the proximal edge of tray 114 is lowered and the distal edge is raised. In the example of Figures 2a to 2d, the load handling device 110 is arranged such that the tipping mechanism 117 is able to rotate the tray 114 to any angle between a first tipped end position and a second tipped end position. In the first tipped end position the tray 114 is tipped such that the distal edge of the tray 114 is at a lowest position, whilst in the second tipped end position the tray 114 is tipped such that the proximal edge of the tray 114 is at a lowest position (i.e. tipped back towards the body 111 of the load handling device 100). When tipping any items from the tray 114, the load handling device 110 may then either tip the tray 114 in the first rotational direction (F) from the carry position towards the first tipped end position or in the second rotational direction (R) from the carry position towards the second tipped end position. By way of example. Figure 4 shows the load handling device 100 of Figures 2a to 2d with the tray 114 in an at least partially extended position and tipped towards a second tipped end position. Enabling the load handling device 100 to tip to opposing first and second tipped end positions provides that the load handling device 110 can deposit items into areas of the destination container 102 that are close to the load handling device 110, thereby ensuring that the entire surface area of the destination container 102 can be utilised. In the example of Figures 2a to 2d, the tipping mechanism 117 comprises a motor 117a arranged to drive a telescopic drive shaft 117b that in turn drives a gear assembly 117c that is configured to translate rotation of the telescopic drive shaft 117b into rotation of the tray 114 around the tipping axis. This arrangement provides that the motor 117a of the tipping mechanism 117 may be disposed and remain within the footprint of the body 111, which improves the stability of load handling device 110, with the telescopic drive shaft 117b then transferring the rotation generated by the motor 117a to the distal end of the corresponding support arm 115 at any point between the retracted and extended positions. In the example of Figures 2a to 2d, the gear assembly 117c is mounted to the distal end of the corresponding support arm 115 and the motor 117a is then mounted to an opposite end of the support arm, with the telescopic drive shaft 117b extending between the motor 117a and the gear assembly 117c. In the example of Figures 2a to 2d, the tray 114 defines a shallow, concave support surface that when horizontal urges items deposited on to the tray 114 towards the lowest point, away from the edges of the tray 114. In a preferred arrangement, the surface of the tray 114 is smooth in order to minimise friction and thereby ensure that items will easily slide off the tray 114. In an alternative arrangement, the tray 114 may be provided with ribs 114a that extend perpendicularly relative to the tipping axis (i.e. longitudinally, from front to back) across the surface of the tray 114. Such ribs 114a can encourage items deposited on to the tray 114 to orient themselves perpendicularly, which assists in minimising the impact force experienced by items when they are tipped off the tray 114. Further alternative arrangements are illustrated in figures 9a, 9b, 10a and 10b. In figures 9a and 9b the tray 230 is a conveyor that is arranged to remain substantially horizontal. Other features of the load handling device are similar to those described above. In this example, the tray 230 is moved to an extended position to be positioned directly above the surface of the destination container 102 and the conveyor operated to carefully deposit the item on a surface beyond the load handling device. In figures 10a and 10b the tray 231 comprises a trap door arrangement that is arranged to remain substantially horizontal. Other features of the load handling device are similar to those described above. In this example, the tray 231 is divided into two doors 232a, 232b. In a carry position, the doors 232a, 232b are closed to support the item 1. When the tray 231 is moved to an extended position directly above the surface of the destination container 102 and trap doors 232a, 232b are opened to carefully deposit the item on a surface beyond the load handling device. The trap door arrangement may be suitable for more delicate items 1. In the example of Figures 2a to 2d, the load handling device 110 further comprises a backstop 120 located immediately behind the proximal edge of the tray 114 and arranged to prevent items from falling off the tray 114. In the illustrated arrangement, the backstop 120 comprises a guide surface that slopes downwards towards the proximal edge of the tray 114, which will therefore urge items on to the tray 114. This arrangement also provides that, if necessary, the load handling device 110 may be configured to implement a carry position in which the tray 114 is tipped towards the backstop 120 such that items on the tray 114 are supported between the tray 114 and the backstop 120. By way of example, Figure 5 shows the load handling device 110 of Figures 2a to 2d in which the tray 114 is in the retracted position and is tipped towards the backstop 120. In this example, the tray 114 is tipped towards the backstop 120 at angle of approximately 10 degrees below the horizontal. Such a configuration may be useful when transporting large items, which may otherwise be more likely to topple off the load handling device 110, as they can then be wedged between the tray 114 and the backstop 12. Similarly, such a configuration may be useful when transporting rounded items, which may otherwise be at risk of rolling off the tray 114, as the combination of the tray 114 and the backstop 120 then provides a deeper recess than the concave surface of the tray 114 alone. The load handling device 110 may then be arranged to move the tray 114 to a substantially horizontal position when stationary at a drop-off point and prior to implementing a deposition operation in which item(s) are tipped from the tray 11. The load handling device 110 is then also arranged to move the tray 114 between an upper position and a lower position when the tray 114 is extended beyond the retracted position. Figures 3a, 3b and 3g show the tray 114 in the upper position, whilst Figure 3d shows the tray 114 in the lower position. Preferably, the load handling device 110 is arranged such that, when in the lower position, the tray 114 is close to the surface of a target destination container 102 so as to minimise the height that item(s) fall when item(s) are unloaded from the tray 114. In particular, in a preferred arrangement the sortation system 100 is arranged such that, when located at a destination zone 104 adjacent to the sortation surface 101, the destination containers 102 are positioned such that a surface of the destination container 102 is lower than the sortation surface 101. This then provides that the height of the load handling device 110 does not need to be increased in order to be able to reach over the side walls of a destination container 102. Consequently, it is preferable that the lower position of the tray 114 is beneath the lowest point of the load handling device 110 (i.e. below the movement means 112, 113) such that the tray 114 can be lowered down to the surface of an adjacent destination container 102. The load handling device 110 is then further arranged such that, when in the upper position, the tray 114 is above the sidewall of a destination container 102 located at a destination zone 104, such that the tray 114 can be extended and retracted without contacting the side wall. The load handling device 110 may be arranged to move the tray 114 to any height between the upper position and the lower position. In particular, the load handling device 110 may be instructed to adjust the height of the tray 114 to anywhere between the upper position and the lower position in dependence upon the nature of the items being deposited and / or the desired location of the items in a target destination container 102. By way of example, if it is desirable to deposit an item on top of another item that is already in a target destination container 102, then the load handling device 110 may be instructed to not lower the tray 114 before tipping the tray 114, or may be instructed to only lower the tray 114 a portion of the distance between the upper position and the lower position. This approach of adapting the height of the tray 114 when depositing an item can save time by optimising the extent to which the tray 114 needs to be lowered for each deposition operation.In the example of Figures 2a to 2d, the load handling device 110 is arranged to tilt the support arms 115 in order to raise and lower the tray 114 when extended beyond the retracted position. The load handling device 110 then further comprises a tilting mechanism 118 that is configured to control the angular position of the support arms 115 relative to the body 111. Specifically, the support arms 115 are pivotally mounted to the body 111 in order to allow the support arms 115 to tilt thereby adjusting the vertical position of the distal ends of the support arms 115 and the tray 114 mounted thereto. In the example of Figures 2a to 2d, the tilting mechanism 118 comprises a pair of linear actuators pivotally mounted between the body 111 and a proximal end of the support arms 115, the proximal end of the support arms 115 being opposite to the distal end to which the tray 114 is mounted. Extension of the linear actuators therefore causes the support arms 115 to rotate around a pivot 119 in a first tiling direction (Ti) such that the distal end of the support arms 115 is lowered, whilst retraction of the linear actuators causes the support arms 115 to rotate around the pivot 119 in an opposite, second tiling direction (Ta) such that the distal end of the support arms 115 is raised. As described above, in the example of Figures 2a to 2d, each of the support arms 115 has a base section 115a mounted to the body 111, with the tray 114 then being mounted towards the distal end of an extending end section 115c that is arranged to extend away from and retract towards the base section 115a. A first end of the base section 115a is then mounted to the body 111 by the pivot 119 such that the base section 115a can rotate relative to the body 111, with the first end of the base section 115a being that from which the extending end section 115c extends. An opposite, second end of the base section 115a is then attached to the body 111 by a pivotally mounted linear actuator of the tilting mechanism 118 such that extension of the linear actuator will cause the support arm 115 to tilt. It will be appreciated that when rotated in the second tiling direction (T2), when in the extended position, the tray 114 will be elevated above the upper position. This position may be preferable when placing items on top of items already placed in the destination container. The load handling device 110 then further comprises various other components required to operate the load handling device 110. For example, these components may include motors that drive the differentially driven wheels 112, batteries that provide electrical energy to power the load handling device 110, and electronics that are involved in the control of the load handling device 110 and communication between the load handling device 110 and the central control facility 106 of the sortation system 100. In the example of Figures 2a to 2d, these components are mounted within the body 111 towards the rear of the load handling device 110 in order to ensure that the centre of gravity of the load handling device 110 is as low and rearward as possible to counterbalance the weight of items in the tray 114 when in the extended position. Preferably, the load handling device 110 is configured to operate as an automated or autonomous vehicle, e.g. an automated guided vehicle (AGV) which is capable of following fixed routes, or an autonomous mobile robot (AMR) which is capable of planning its own routes. The load handling device 110 may therefore also comprise any components necessary in order to allow the load handling device 110 to function as an automated or autonomous vehicle, such as sensors, memory, processors, transceivers etc. A method of operating the load handling device 110 of Figures 2a to 2d in order to deposit an item will now be described with reference to Figures 3a to 3g. The central control facility 106 provides instructions to the load handling devices 110 that includes information directing the load handling device 110 to a pickup point within a supply zone 103 and to a corresponding drop-off point adjacent to a destination zone 104 at which a target destination container 102 is present. The load handling device 110 then travels to the pickup point within the supply zone 103 and receives one or more items before travelling to the drop-off point. Whilst travelling, the load handling device 110 retains the tray 114 in the retracted position, such that a majority of the tray 114 is within the footprint of the body 111, and such that the tray 114 is in the carry and upper positions. Once located at the drop-off point, the load handling device 110 then initiates the movement of the tray 114 from the retracted position to the extended position. To do so, the load handling device 110 uses the extension mechanism to drive the extension of the support arms 115 from the retracted position, which in turn results in the extension of the telescopic drive shaft 117b. During this extension step, the load handling device 110 retains the tray 114 in the carry and upper positions. In particular, the load handling device 110 uses the tilting mechanism 118 to retain the tray 114 in the upper position and uses the tipping mechanism 117 to retain the tray 114 in the carry position. When in the extended position, the tray 114 is then disposed over a designated area of the target destination container 102, as shown in Figure 3b. The load handling device 110 then initiates the movement of the tray 114 from the upper position towards the lower position. To do so, the load handling device 110 uses the tilting mechanism 118 to drive the tilting of the support arms 115 so as to lower the tray 114 from the upper position towards the lower position. In the illustrated arrangement, the linear actuators of the tilting mechanism 118 extend so as to cause the support arms 115 to rotate around the pivot 119 in the first tiling direction (Ti) such that the distal ends of the support arms 115 are lowered. During this tilting step, the load handling device 110 retrains the tray 114 in the carry position. In particular, the load handling device 110 uses the tipping mechanism 117 to retain the tray 114 in the carry position by rotating the tray 114 in the second rotational direction (R2), in opposition to the tilting of the support arms 115 in the first tiling direction (Ti). When in the lower position, the tray 114 is then disposed vertically closer to the surface of the target destination container 102, as shown in Figure 3d. The load handling device 110 then initiates the tipping of the item from the tray 114 into the target destination container 102. To do so, the load handling device 110 uses the tipping mechanism 117 to drive the rotation of the tray 114 in the first rotational direction (Ri) from the carry position towards a tipped end position. In the illustrated arrangement, the load handling device 110 simultaneously raises and retracts the tray 114, at least partially, as shown in Figure 3e. To do so, the load handling device 110 uses the extension mechanism 116 to drive the partial retraction of the support arms 115 from the extended position towards the retracted position and partially retracts the linear actuators of the tilting mechanism 118 so as to cause the support arms 115 to rotate around the pivot 119 in the second tiling direction (T2) such that the distal ends of the support arms 115 are raised. Raising the tray 114 during the tipping step allows the lower edge of the tray 114 to remain close to or in contact with the surface of the target destination container 102 whilst the tray 114 is being tipped, so as to minimise the risk of an item falling from the tray 114, without the destination container 102 blocking the tipping movement of the tray 114. Retraction of the tray 114 during the tipping step then assists with withdrawing the tray 114 from beneath the item(s) being deposited and sliding the item(s) off the tray 114 without unnecessarily tipping the item(s) themselves. After the item(s) have been tipped from the tray 114, load handling device 110 then initiates the levelling of the tray 114 and continues the retraction and raising of the tray 114. To do so, the load handling device 110 uses the tipping mechanism 117 to drive the rotation of the tray 114 in the second rotational direction (R2) towards the carry position, as shown in Figure 3f. The load handling device 110 also uses the tilting mechanism 118 to the drive the rotation of the support arms 115 around the pivot 119 in the second tiling direction (T2) such that the distal ends of the support arms 115 are raised to the upper position, and uses the extension mechanism 116 to drive the partial retraction of the support arms 115 to the retracted position, as shown in Figure 3g. Preferably, the retraction of the support arms 115 by the extension mechanism 116 and the rotation of the tray 114 towards the carry position by the tipping mechanism 117 is substantially simultaneous and is coordinated so as to ensure that the tray 114 does not contact either the just deposited item(s) or the side walls of the destination container 102. The load handling device 110 then moves away from the target destination container 102 and is free to travel back to the supply zone 103 in order to collect further item(s) that require sorting. In addition to depositing items into a destination container 102, a load handling device 110 such as that illustrated in Figures 2a to 2d may also be used to reposition items already located within a destination container 102. To do so, the load handling device 110 tips the tray 114 towards a tipped end position and, if necessary, lowers the tray 114 towards the lower position, and then uses the tipped tray 114 as a blade to push and / or pull items across the surface of a destination container 102. Then, if an item has moved into an undesirable position within a destination container 102, a load handling device 110 can be used to reposition the items in the tray 114 without need for any other device or system, or direct intervention from a human. Figure 6a illustrates a top-down view of the support arms 115 of the load handling device 110 of Figures 2a to 2d, together with the extension mechanism 116 and tipping mechanism 117. Figure 6b then illustrates a side-on view in which a portion of a housing has been removed from the gear assembly 117c of the tipping mechanism 117. As described above, each of the support arms 115 is provided by a telescopic linear rail that comprises a base section 115a mounted to the body 111, an extending intermediate section 115b movably mounted to the base section 115a, and an extending end section 115c movably mounted to the extending intermediate section 115b. In this example, the extension mechanism 116 that is arranged to extend and retract the support arms 115 comprises a motorised pulley system. The tipping mechanism 117 then comprises a gear assembly 117c mounted adjacent to the distal end of the extending end section 115c, a motor 117a mounted adjacent to an opposite end of the base section 115a, and a telescopic drive shaft 117b that extends between the motor 117a and the gear assembly 117c. The telescopic drive shaft 117b therefore rotates around an axis that is parallel to the extension and retraction direction of the tray 114, whereas the tipping axis of the tipping mechanism 117 is perpendicular to the extension and retraction direction of the tray 114. The gear assembly 117c is therefore required to translate the rotation of the telescopic drive shaft 117b by 90 degrees in order to drive the tipping of the tray 114 around the tipping axis. In the example shown in Figure 4b, the gear assembly 117c comprises a bevel gear attached to a distal end of the telescopic drive shaft 117b that cooperates with a spur or straight-cut gear in order to translate rotation of the telescopic drive shaft 117b by 90 degrees. However, any other suitable arrangement of gears could be used. Figure 7 then illustrates an alternative example of a load handling device 210 suitable for use with the sortation system 100 of Figure 1. The load handling device 210 of Figure 7 is substantially similar to that of Figures 2a to 2d. However, in contrast with the load handling device 110 of Figures 2a to 2d, the load handling device 210 of Figure 7 further comprises a stabilising mechanism mounted to the body 211 that is arranged to assist with stabilising the load handling device 210 when implementing a deposition operation in which item(s) are tipped from the tray 214. In particular, the stabilising mechanism comprises engagement devices 221, 222 mounted to the body 211 of the load handling device 210 that are arranged to engage with cooperating features provided on a destination container 102. Figure 8 therefore shows the stabilising mechanism in isolation and engaged with a destination container 102. The engagement of the load handling device 210 with the destination container 102 serves to anchor the load handling device 210 in order to prevent the load handling device 210 from toppling when the tray 214 is extended beyond the footprint of the body 211. In the example of Figures 7 and 8, the engagement devices 221, 222 comprise first engagement devices 221 and second engagement devices 222. Each of the first engagement devices 221 comprises a prong or projection that extends forward from the body 211 of the load handling device 210. The destination containers 102 then comprise cooperating features in the form of corresponding sockets 102a provided on the side walls of the destination container 102, with each of the first engagement devices 221 being arranged to fit within a corresponding socket 102a. Each of the second engagement devices 222 comprises a set of rollers that are mounted forward of the body 211 of the load handling device 210 and that are arranged to engage cooperating features that are provided by an upper edge 102b of the side wall of the destination container 102. When approaching a destination container 102, the load handling device 210 aligns each of the prongs that provide the first engagement devices 221 with a corresponding socket 102a on a side wall of the destination container 102 and locates each first engagement device 221 within the corresponding socket 102a. Providing a destination container 102 with a plurality of sockets 102a along each side wall of the destination container 102 then allows a load handling device 210 to engage with the destination container 102 at multiple different positions such that the load handling device 210 can deposit items into different areas within the destination container 102. When approaching a destination container 102, the rollers of the second engagement devices 222 move over an upper edge of the side wall of the destination container 102. The engagement of the first and second engagement devices 221, 222 with the destination container 102 then prevents the load handling device 210 from toppling forwards when the load-bearing tray 214 is in the extended position. Whilst in the example of Figures 7 and 8 the stabilising mechanism of the load handling device 210 comprises both prongs and rollers, the stabilising mechanism may comprise just one of these types of engagement device. In particular, the load handling device 210 may have prongs but no rollers or rollers but no prongs. In an alternative arrangement, the stabilising mechanism may comprise one or more engagement devices that each comprise a clamp or catch that is arranged to releasably engage an upper edge of the destination container 102 when the load handling device 210 is immediately adjacent to the destination container 102. In a further alternative arrangement, the stabilising mechanism may comprise one or more engagement devices that are arranged to engage with the sortation surface 101, rather than a destination container 102. For example, the or each engagement device may comprise a permanent or electromagnet that is arranged to magnetically interact with the sortation surface 101 itself, or with magnetic rails or pads embedded within the sortation surface 101, and thereby resist the separation of the load handling device 210 from the sortation surface 101. As an alternative example, the or each engagement device may comprise a projection extending from the bottom of the load handling device 210 and arranged to function as a runner or glider when located within a track embedded within the sortation surface 101. As a further example, the or each engagement device may comprise a retractable anchor that is arranged to engage with anchor points embedded within the sortation surface 101 (e.g. at drop-off points). It will be appreciated that the features described hereinabove may all be used together in a single system. In other embodiments of the invention, some of the features may be omitted. The features may be used in any compatible arrangement. Many variations and modifications not explicitly described above are possible without departing from the scope of the invention as defined in the appended claims. It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. By way of example, in the arrangements illustrated in the Figures the tray is mounted to the body by a pair of moveable support arms, one on either side of the tray. However, in an alternative arrangement, the tray may be mounted to the body by a single support arm or more than two support arms. By way of further example, in the arrangements illustrated in the Figures almost the entirety of the tray is disposed within the footprint of the body when in the retracted position. In particular, as shown in Figure 2d, only a front edge of the tray is outside of the footprint of the body when in the retracted position. However, in an alternative arrangement, the entirety of the tray may be disposed within the footprint of the body when in the retracted position. Furthermore, a larger portion of the tray could be outside of the footprint of the body when in the retracted position provided that the centre of the tray is within the footprint, such that the majority of the tray is disposed within the footprint of the body when in the retracted position. By way of yet further example, in the arrangements illustrated in the Figures the tilting mechanism comprises a pair of linear actuators pivotally mounted between the body and a proximal end of the support arms. However, any suitable tilting mechanisms may be used, such as a tipping motor arranged to rotate the support arms around a pivot. By way of yet further example, the tray may be from a compliant material, and the support arms arranged to move in the Y direction. The arms may be moved towards each other in order to bend the tray into a funnel shape in order to direct placement of items.

Claims

1. A load handling device comprising:a body mounted on movement means;a tray arranged to carry one or more items, the tray being mounted to the body by one or more support arms, the one or more support arms being arranged to move the tray between a retracted position and an extended position;wherein in the retracted position the tray is disposed at least partially within a footprint of the body and in the extended position the tray is disposed away from the body; and wherein the load handling device is arranged to allow the tray to be tipped when extended beyond the retracted position.

2. The load handling device according to claim 1, wherein the tray is rotationally mounted to the one or more support arms in order to allow the tray to tip.

3. The load handling device according to any of claims 1 and 2, wherein the load handling device is arranged to tip the tray away from a carry position.

4. The load handling device according to claim 3, wherein the load handling device is arranged to tip the tray from the carry position towards a tipped end position.

5. The load handling device according to claim 4, wherein the load handling device is arranged to tip the tray between a first tipped end position and a second tipped end position, wherein the carry position is between the first tipped end position and the second tipped end position.

6. The load handling device according to any of claims 4 and 5, wherein the carry position is substantially horizontal.

7. The load handling device according to any of claims 1 to 6, and further comprising a backstop mounted to the body and located immediately behind the tray when in the retracted position.

8. The load handling device according to claim 7 when dependent upon claim 3, wherein the carry position is any of (i) substantially horizontal and (ii) tipped towards the backstop when in the retracted position.

9. The load handling device according to any of claims 1 to 8, wherein the tray comprises a conveyor, OR wherein the tray comprises a trap door arrangement.

10. The load handling device according to any of claims 1 to 8, and further comprising a tipping mechanism arranged to tip the tray.

11. The load handling device according to claim 10, wherein the tipping mechanism comprises a motor, a telescopic drive shaft and a gear assembly, the motor being arranged to drive the telescopic drive shaft and the gear assembly being arranged to translate rotation of the telescopic drive shaft into rotation of the tray.

12. The load handling device according to claim 11, wherein the motor remains within the footprint of the body and the telescopic drive shaft is arranged to extend and retract with the tray.

13. The load handling device according to any of claims 1 to 12, wherein the load handling device is arranged to allow the tray to be lowered or elevated and tipped when extended beyond the retracted position.

14. The load handling device according to claim 13, wherein the load handling device is arranged to move the tray from an upper position towards a lower position when the tray is extended beyond the retracted position, or from an upper position to towards and elevated position when the tray is extended beyond the retracted position.

15. The load handling device according to any of claims 13 and 14, wherein the load handling device is arranged to tilt the one or more support arms in order to lower or elevate the tray when extended beyond the retracted position.

16. The load handling device according to claim 15, wherein each of the one or more support arms is pivotally mounted to the body in order to allow the support arm to tilt relative to thebody and thereby move the tray between the upper position, the lower position and the elevated position.

17. The load handling device according to any of claims 15 and 16, wherein the load handling device further comprises a tilting mechanism that is configured to control the angular position of each of the one or more support arms relative to the body.

18. The load handling device according to claim 17, wherein the tilting mechanism comprises one or more linear actuators, each of the one or more linear actuators being pivotally mounted between the body and the one or more of the support arms.

19. The load handling device according to any of claims 1 to 18, wherein each of the one or more support arms is extendable in order to allow the tray to move between the retracted position and the extended position.

20. The load handling device according to claim 19, wherein each of the one or more support arms comprises a base section mounted to the body and an extending end section movably mounted to the base section, the tray being mounted to the extending end section.

21. The load handling device according to any of claims 1 to 20, and further comprising:a stabilising mechanism mounted to the body, the stabilising mechanism comprising one or more engagement devices arranged to engage cooperating features providing on one or more of (i) a surface on which the load handling device operates and (ii) a destination container.

22. A sortation system comprising:a sortation surface, a plurality of destination containers disposed adjacent to the sortation surface and a plurality of load handling devices according to any of claims 1 to 21, wherein the plurality of load handling devices are arranged to travel on the sortation surface and to deposit items into the destination containers.

23. A method of operating a load handling device in order to deposit an item into a destination container, the method comprising:receiving the item in a tray of the load handling device;travelling across a sortation surface to a drop-off point adjacent to the destinationcontainer;moving the tray from a retracted position towards an extended position such that the tray is disposed over the destination container; androtating the tray from a carry position towards a tipped end position such that the item is tipped from the tray into the destination container.

24. The method of operating a load handling device according to claim 23, and further comprising:after tipping the item from the tray:rotating the tray back towards the carry position;moving the tray back towards the retracted position.

25. The method of operating a load handling device according to any of claims 23 and 24, and further comprising:after moving the tray from a retracted position towards an extended position:lowering the tray from an upper position towards a lower position or raising the tray from an upper position towards an elevated position.

26. The method of operating a load handling device according to claim 25, and further comprising:after tipping the item from the tray:respectively raising or lowering the tray back towards the upper position.

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