Winch Assembly for Load Handling Equipment

Abstract

A robotic load handling device for lifting and moving storage containers stacked in a grid framework structure comprising a track system comprising first and second sets of tracks arranged in a grid pattern, the robotic load handling device comprising: a wheel assembly comprising first and second sets of wheels arranged to engage the first or second sets of tracks, a wheel positioning mechanism for selectively engaging either the first set of wheels with the first set of tracks or the second set of wheels with the second set of tracks, a container lifting mechanism 251 comprising a container gripping assembly configured to releasably grip a container, and a lifting drive assembly configured to raise and lower the container gripping assembly. The lifting drive assembly comprises a single motor 252 configured to raise the container gripping assembly in a first rotational direction and lower the container gripping assembly in a second rotational direction. The container lifting mechanism 251 further comprises a first set of spools 257, 262 and a second set of spools 267, 268, where each spool of the first and second sets of spools carries a lifting tether 38 having a first end fixed to the container gripping assembly and a second end fixed to its respective spool, a drive pulley 253 connected to rotate with a single motor 252, and a plurality of timing pulleys 255, 261, 263, 265 connected to rotate with the first and second sets of spools 257, 262, 267, 268 and the drive pulley 253 such that the single motor 252 is configured to rotate the first and second sets of spools to raise and lower the container gripping assembly.The plurality of timing pulleys includes a first timing pulley 255 and a second timing pulley 261, the first timing pulley 255 and the second timing pulley 261 are rotationally connected to the drive pulley 253 by a single timing belt 254 forming a closed loop around the first timing pulley 255 and the second timing pulley 261 and the drive pulley 253 such that the drive pulley 253 drives the rotation of the first timing pulley 255 and the second timing pulley 261 in the same rotational sense, the first timing pulley 255 is disposed between the drive pulley 253 and the second timing pulley 261, and the lift drive assembly includes a first timing pulley 255 and a second timing pulley 261, the first timing pulley 255 and the second timing pulley 261 are rotationally connected to the drive pulley 253 by a single timing belt 254 forming a closed loop around the drive pulley 253 such that the drive pulley 253 drives the rotation of the first timing pulley 255 and the second timing pulley 261 in the same rotational sense .... The single timing belt 254 further includes a belt tensioning wheel 266a arranged between the timing pulley 255 and the second timing pulley 261, the belt tensioning wheel 266a being arranged to urge the single timing belt 254 against the first timing pulley 255 so that the tension in a first section T1 of the single timing belt 254 between the first timing pulley 255 and the drive pulley 253, which, in use, moves in a direction towards the drive pulley, is greater than the tension in a second section T2 of the single timing belt 254 between the first timing pulley 255 and the second timing pulley 261 when the single motor 252 rotates in a first rotational direction.

Description

[Technical field]

[0001] The present invention relates to the field of robotic load handling devices for handling storage containers or bins in automated storage systems comprising stacked containers arranged in a grid framework structure, and more particularly to winch assemblies for robotic load handling devices. [Background technology]

[0002] Storage and retrieval systems comprising a three-dimensional storage grid structure within which storage containers / receptacles are stacked on top of one another are known. PCT Publication No. WO2015 / 185628A (Ocado) describes a known storage and fulfilment system in which a stack of receptacles or containers is arranged within a grid framework structure. The receptacles or containers are accessed by robotically controlled load handling devices operable on tracks located on top of the grid framework structure. A system of this type is illustrated diagrammatically in Figures 1 to 3 of the accompanying drawings.

[0003] As shown in Figures 1 and 2, stackable containers known as bins 10 are stacked on top of each other to form a stack 12. For definition purposes, the terms "bin", "tote", "container" and "storage container" are used interchangeably in the description to refer to the same feature. The stack 12 is arranged in a grid framework structure 14 in a warehouse storage or manufacturing environment. The grid framework structure is made up of a number of storage columns or grid columns. Each grid cell in the grid framework structure has at least one grid column for storage of a stack of containers. Figure 1 is a schematic perspective view of the grid framework structure 14, and Figure 2 is a top-down view showing the stack 12 of bins 10 arranged within the framework structure 14. Each bin 10 typically holds a number of product items (not shown), which may be of different product types or may be the same depending on the application.

[0004] The grid framework structure 14 comprises a plurality of upright members 16 supporting horizontal grid members 18, 20. A first set of parallel horizontal grid members 18 are arranged at right angles to a second set of parallel horizontal grid members 20 to form a plurality of horizontal grid cells supported by the upright members 16. The members 16, 18, 20 are typically fabricated from metal. The containers 10 are stacked between the members 16, 18, 20 of the grid framework structure 14 such that the grid framework structure 14 prevents horizontal movement of the stack 12 of containers 10 and guides vertical movement of the containers 10.

[0005] The top level of the grid framework structure 14 includes rails or tracks 22 arranged in a grid pattern across the top of the stacks 12. With further reference to FIG. 3, the rails 22 support a plurality of load handling apparatuses 30. A first set 22a of parallel rails 22 guide movement of the robotic load handling apparatus 30 in a first direction (e.g., X direction) across the top of the grid framework structure 14, and a second set 22b of parallel rails 22 arranged perpendicular to the first set 22a guide movement of the load handling apparatus 30 in a second direction (e.g., Y direction) perpendicular to the first direction. In this manner, the rails 22 allow movement of the robotic load handling apparatus 30 laterally in two dimensions in the horizontal XY plane, such that the load handling apparatus 30 may be moved to a position above any stack 12.

[0006] A known load handling apparatus 30, shown in Figure 4, comprises a vehicle body 32 and is described in PCT Patent Publication No. WO2015 / 019055 (Ocado), which is incorporated herein by reference. Here, the load handling apparatus 30 comprises a wheel assembly comprising a first set of wheels 34, consisting of a pair of wheels at the front of the vehicle 32 and a pair of wheels 34 at the rear of the vehicle 32, for engaging a first set of rails or tracks for guiding movement of the apparatus in a first direction, and a second set of wheels 36, consisting of a pair of wheels 36 on each side of the vehicle 32, for engaging a second set of rails or tracks for guiding movement of the apparatus in a second direction. The vehicle body of the load handling apparatus comprises an upper portion and a lower portion. The wheels are arranged in the lower portion of the vehicle body around the periphery of a cavity or recess known as a container receiving recess 40. The load handling apparatus 30 as shown in FIG. 5 comprises a container lifting mechanism comprising a lifting drive assembly or winch assembly comprising a winch or crane mechanism for lifting storage containers or receptacles also known as totes from above, and a container gripping assembly or grabber device 39. The lifting mechanism is located on the upper part of the vehicle body. The grabber device is formed as a frame with four corner sections. The winch crane assembly comprises a lifting tether 38 wound on a spool or reel (not shown). Typically, the winch assembly comprises four spools, each of which carries a lifting tether having one end fixed to the spool and the other end fixed to a corner of the grabber device.

[0007] The container gripping assembly 39 is configured to grip the top of the storage container 10 in order to lift the storage container 10 from a stack of containers in a storage system of the type taught in PCT Patent Publication No. WO2015 / 019055 (Ocado). The winch assembly is driven by a drive mechanism (not shown), commonly known as a Z motor because the Z motor is configured to raise and lower the container gripping assembly in the Z direction as the storage container is lifted and lowered. During operation of the drive mechanism to lower the container gripping assembly, a lifting tether is paid out from the spool.

[0008] During the picking operation, especially when engaging with a storage container, it is essential that the container gripping assembly always remains horizontal, otherwise there is a potential risk that at least one of the lifting tethers holding the container gripping assembly may break if subjected to unbalanced and high loads. In order to have the necessary physical properties (Young's modulus) to withstand the load of a storage container, which can weigh as much as 35 kg, the lifting tethers are generally in the form of tapes or bands, usually made of metal (generally alloy steel). Typically, the container gripping assembly is configured as a frame, and four lifting tapes wound on separate spools are used to suspend the frame from the body of the load handling equipment. Conventionally, the lifting tethers wound on separate spools are located in the upper level of the housing or body of the load handling equipment. Separate motors are used to drive each of the four spools to raise and lower the container gripping assembly. Due to the increased weight and complexity of having separate motors to drive the four spools, recent developments have moved towards the use of a single motor and pulley system to raise and lower the container gripping assembly. WO2021 / 148657 (Ocado Innovation Limited) describes a lifting drive assembly comprising a single motor and multiple timing pulleys, timing belts, and / or gears configured to transmit rotation from the output of the single motor to raise and lower the container gripping assembly. The timing pulleys and their respective timing belts engage via teeth and corresponding grooves or recesses. In one particular embodiment of WO2021 / 148657 (Ocado Innovation Limited), a single timing belt is described for connecting the single motor to the multiple timing pulleys.

[0009] To ensure that the container gripping assembly remains level, it is important that the length of all tapes remain the same at all times during operation of the container gripping assembly. To ensure that the lengths of all tethers secured to the container gripping assembly are equal and therefore the container gripping assembly remains level during operation, the length of each of the tapes must be adjusted both initially and at various maintenance intervals. Adjustments are required because the tapes tend to stretch or elongate over time, which can be due to a number of factors such as the environment, motor wear, tape stretching, etc. In the extreme case where the length of any one of the tapes is not equal, the container gripping assembly may fail to engage the container, either because it does not drop enough or because it overshoots the container.

[0010] The lifting drive assembly itself may also play a role in influencing the orientation of the container gripping assembly as it is raised and lowered. As the four lifting tethers are fixed to the container gripping assembly, if any one of the timing pulleys connecting the single motor to the container gripping assembly slips or skips a tooth from one of their respective pulleys, this may cause any one of the spools carrying the lifting tethers to be out of kilter, i.e., lagging behind, with the other spools. This in turn may cause any one of the lifting tethers to be less unwound than the other spools. This problem is exacerbated when a single belt is used to connect a single motor to multiple timing pulleys that are used to drive multiple spools, as described in WO2021 / 148657 (Ocado Innovation Limited). Tension applied to the timing belt from a single motor may cause the belt to stretch, resulting in a section of the timing belt becoming loose, increasing the risk that the timing belt may become disengaged from the timing pulleys. The timing belt stretching problem is especially exacerbated when the lifting mechanism picks up fully loaded storage containers, which can weigh as much as 35 kg, because the high torque of the single motor when picking up a fully loaded storage container is transmitted through the timing belt to the timing pulleys. Because multiple spools are driven by multiple timing pulleys, slippage or disengagement of the timing belt connecting one or more of the timing pulleys can cause one or more lifting tethers to be wound differently on their respective spools, which in turn can cause the container gripping assemblies secured to these lifting tethers to become uneven. The unevenness when the container gripping assembly is engaged with the storage container can result in the storage container fouling against the vertical uprights of the grid framework structure, or in the worst case, the storage container can become jammed between the vertical uprights.Even if belt tensioning is provided to ensure that the tension of the timing belt is maintained during operation of a single motor, the use of belt tensioning only maintains the tension of the timing belt over a fixed, predetermined range of tension dictated by the tension of the belt tensioning, and the problem of belt stretching still exists when the tension of the timing belt exceeds the tension provided by the belt tensioning.

[0011] To correct for the container gripping assembly being uneven, it may be necessary to remove any slack in the reel by disconnecting the spool or reel from its rotating shaft and adjusting the tape by free rotation of the reel or spool relative to the rotating shaft. The reel or spool is then attached to the rotating shaft once the band has the desired length. A variation of this method is to provide adjustable lifting band connectors fixed to the container gripping assembly, as taught in WO2019 / 206438 (Autostore Technology). Each adjustable lifting connector comprises a bracket and a band connector hub. The bracket is connected to the container gripping assembly, and the band connector hub is connected to one of the lifting bands and to the bracket such that movement of the band connector hub relative to the bracket will adjust the vertical distance between the respective corner section of the container gripping assembly and the lifting band drive assembly.

[0012] SUMMARY OF THE PRESENT EMBODIMENT It is therefore a primary object of the present invention to provide a single motor based lifting drive mechanism for raising and lowering a container gripping assembly which does not suffer from the above mentioned problems. Summary of the Invention

[0013] The present invention mitigates the above problem by controlling the length of the section or segment of the timing belt under tension when connected to a single motor of the storage container lifting drive assembly. Applying the principles of Hooke's Law, the longer the length of the timing belt under tension, the greater the percentage of stretching of the timing belt and the greater the resulting slack in the timing belt, which increases the risk of the timing belt slipping on the timing pulley. Thus, the shorter the length of the timing belt under tension, the smaller the percentage of the timing belt that is under strain, thus reducing the risk of the timing belt slipping on the timing pulley. Since the torque of the motor is transferred to the timing belt when picking up a storage container, which can weigh up to 35 kg, timing belt slippage is more of an issue when raising the container gripping assembly than when lowering the container gripping assembly, which is more affected by gravity.

[0014] There are belt tensioning or guiding wheels that press the back side of the timing belt and make it take a serpentine shape with respect to the timing pulleys to allow the timing belt to pass over at least three timing pulleys with a wrap angle large enough to prevent the timing belt from slipping. The belt tensioning wheels are configured to urge the timing belt against the timing pulleys in the sense that they apply a force in a direction perpendicular to the tangential force of the timing belt on the timing pulleys. The amount of tension applied to different sections or segments of the timing belt can be controlled by controlling the position of the belt tensioning or guiding wheels with respect to the timing pulleys in the pulley system. The tension depends on the direction of rotation of the timing pulleys to raise or lower the container gripping assembly. The shorter the length of the timing belt between the belt tensioning wheels and the single motor that is under tension, the lower the risk of the timing belt slipping because a shorter timing belt is stretched during the operation of the single motor. Since the tension in the timing belt is greatest when the single motor pulls the timing belt toward the single motor, i.e., when the single motor is configured to raise the container gripping assembly, the belt tensioning wheel is positioned so that the tension in the timing belt is concentrated in the area of ​​the timing belt between the belt tensioning wheel and the single motor, which is moving in a direction toward the single motor. Since the belt tensioning wheel is configured to urge the timing belt against the timing pulley, the tension in the timing belt is highest between the motor and the timing pulley closest to the single motor, which is moving in a direction toward the single motor. Since this is a small section of the timing belt, any stretch in this section of the timing belt is minimal.

[0015] The present invention provides a robotic load handling apparatus for lifting and moving containers stacked in a stack on a grid framework structure including a first set of tracks extending in a first direction above the stack of containers and a second set of tracks extending in a second direction transverse to the first direction, the load handling apparatus being configured to move on the tracks above the stack, the load handling apparatus comprising: a wheel assembly comprising a first set of wheels for engaging a first set of tracks to guide movement of the load handling apparatus in a first direction and a second set of wheels for engaging a second set of tracks to guide movement of the load handling apparatus in a second direction; a wheel positioning mechanism for selectively engaging either the first set of wheels with the first set of tracks or the second set of wheels with the second set of tracks, where the wheel positioning mechanism is configured to raise or lower the first set of wheels or the second set of wheels with respect to the body, thereby enabling the load handling apparatus to selectively move in either a first direction or a second direction over the tracks of the grid framework structure; a container lifting mechanism comprising a container gripping assembly configured to releasably grip a container, and a lifting drive assembly configured to raise and lower the container gripping assembly; the lift drive assembly includes a single motor configured to raise the container gripping assembly in a first rotational direction and to lower the container gripping assembly (43) in a second rotational direction; a first set of spools and a second set of spools, where each spool of the first and second sets of spools carries a lifting tether having a first end fixed to the container gripping assembly and a second end fixed to its respective spool; a drive pulley connected for rotation with a single motor; a plurality of timing pulleys connected for rotation with the first and second sets of spools and the drive pulley such that a single motor is configured to rotate the first and second sets of spools to raise and lower the container gripping assembly; the plurality of timing pulleys comprises a first timing pulley and a second timing pulley, the first and second timing pulleys being rotatably connected to a drive pulley by a single timing belt forming a closed loop around the first and second timing pulleys and the drive pulley such that the drive pulley drives rotation of the first and second timing pulleys in the same rotational sense; The first timing pulley is disposed between the drive pulley and the second timing pulley, and the lifting drive assembly further comprises a belt tensioning wheel disposed between the first timing pulley and the second timing pulley, the belt tensioning wheel being arranged to urge the single timing belt against the first timing pulley such that a tension in a first section of the single timing belt between the first timing pulley and the drive pulley, which, in use, moves in a direction towards the single motor when the single motor rotates in a first rotational direction, is greater than a tension in a second section of the single timing belt between the first timing pulley and the second timing pulley.

[0016] The first and second timing pulleys are in contact with the inner surface of the timing belt such that the first and second timing pulleys, and therefore their respective spools, are driven in the same rotational direction. Optionally, a belt tensioning wheel allows the timing belt to be passed over the first and second timing pulleys and the drive pulley in a serpentine shape, thus allowing a larger wrap angle of the timing belt around the first timing pulley. Thus, the timing belt in the area where the belt tensioning wheel urges the single timing belt against the first timing pulley may be defined as the serpentine area of ​​the single timing belt. The terms "single timing belt" and "timing belt" are used interchangeably herein to mean the same feature. The term timing belt may encompass a rubber belt or a chain. Preferably, the length of the first section of the single timing belt is shorter than the second section of the belt. The second section of the single timing belt can be any section of the single belt that runs from the first timing pulley through the second timing pulley to the drive pulley, i.e., from the first timing pulley around the second timing pulley to the drive pulley. This includes the segment of the single timing belt between the first and second timing pulleys.

[0017] The shorter the length of the first section of the timing belt, the less the amount of the timing belt under tension and therefore the less the rate at which the timing belt stretches. There are various configurations of belt tensioning wheels for controlling the tension of the timing belt, which are highly dependent on the direction of rotation of the spool when raising the container gripping assembly, since the tension is greatest in the segment of the timing belt that is pulled toward the drive pulley (the drive pulley is connected to rotate to the single motor). In one example, the belt tensioning wheels are arranged to urge the single timing belt against the underside of the first timing pulley when the first rotation direction is counterclockwise and the second rotation direction is clockwise, so that the first section of the single timing belt (the lower portion of the single timing belt) assumes a serpentine shape. In another example, the belt tensioning wheel is positioned to urge the single timing belt against an upper side of the first timing pulley when the first rotational direction is a clockwise direction and the second rotational direction is a counterclockwise direction, so that a first section of the single timing belt (an upper portion of the single timing belt) assumes a serpentine shape.

[0018] There are different arrangements for connecting the multiple timing pulleys to a single motor to drive the rotation of the first and second sets of spools. Optionally, the first timing pulley and the first set of spools are mounted for rotation on the lifting shaft such that the lifting shaft is common to the first set of spools and the first timing pulley. Optionally, at least one of the second set of spools is driven by a single motor by being connected to the lifting shaft by a second timing belt. In this example, the second set of spools are each mounted for rotation on a separate shaft and are driven for rotation by being connected to a single motor by both a timing belt and a second timing belt. In this arrangement, preferably, the lifting drive assembly further comprises a third pulley mounted for rotation on the lifting shaft and a fourth pulley connected for rotation to at least one of the second set of spools, the second timing belt forming a closed loop around the third pulley and the fourth pulley such that the lifting shaft drives the rotation of at least one of the second set of spools. To maintain tension of the second timing belt, the lifting drive assembly preferably further comprises a second belt tensioning wheel arranged to urge the second timing belt against the third pulley. Preferably, the second belt tensioning wheel makes it possible to increase the wrap angle of the second timing belt around the third pulley, so that the second timing belt assumes a serpentine shape around the third and fourth timing pulleys.

[0019] In another example for driving the rotation of the first and second sets of spools by a single motor, the first and second sets of spools are each mounted on separate lifting shafts connected to the single motor by a single timing belt. Preferably, the lifting drive assembly further comprises a second lifting shaft, the lifting shafts defining a first lifting shaft, the second lifting shaft being substantially parallel to the first lifting shaft, the second set of spools and the second timing pulley being mounted for rotation on the second lifting shaft, the second lifting shaft being connected to the first lifting shaft by a single timing belt, thereby being rotated by the single motor.

[0020] To control the wrap angle of the timing belt on the first timing pulley, preferably the belt tensioning wheel is adjustable to adjust the force of the single timing belt on the first timing pulley, thereby controlling the wrap angle of the timing belt around the first timing pulley.

[0021] Optionally, the container lifting mechanism comprises a communications spool carrying a communications cable for sending and / or receiving communication signals to and from the container gripping assembly, the communications cable having a first end connected to the communications spool and a second end connected to the container gripping assembly, the communications spool being mounted for rotation on the lifting shaft such that a single motor is configured to raise and lower the second end of the communications cable together with the container gripping assembly.

[0022] Optionally, the robotic load handling apparatus comprises a vehicle body having an upper portion and a lower portion, the upper portion configured to house one or more operating components, the lower portion being disposed below the upper portion, and the lower portion comprising a container receiving space for accommodating at least a portion of a container.

[0023] A single motor preferably drives the first set of spools and the second set of spools synchronously to ensure that the orientation of the container gripping assemblies is substantially horizontal when raising and lowering the container gripping assemblies, with the lengths of each of the lifting tethers extending between the container gripping assemblies and their respective spools being substantially equal.

[0024] The present invention further provides a storage system comprising: a track system comprising a first set of parallel tracks and a second set of parallel tracks, where the first set of parallel tracks extend in a first direction and the second set of tracks extend in a second direction, the first direction being substantially perpendicular to the second direction such that the tracks are arranged in a grid pattern including a plurality of grid spaces or grid cells; a stack of containers positioned under the rail system, where each of the stacks of containers occupies a single grid space or grid cell; A load handling apparatus according to the present invention arranged to traverse along the track system over a plurality of grid spaces or grid cells such that when positioned above a stack of containers occupying said grid spaces or grid cells, the container lifting mechanism is configured to lift at least one container from said stack of containers.

[0025] Further features and aspects of the present invention will become apparent from the following detailed description of illustrative embodiments that proceeds with reference to the drawings. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram of a grid framework structure according to a known system. [Diagram 2] FIG. 2 is a schematic diagram from a top-down view showing a stack of containers arranged within the framework structure of FIG. [Diagram 3]FIG. 3 is a schematic diagram of a known storage system showing load handling equipment operable on a grid framework structure. [Figure 4] FIG. 4 is a schematic perspective view of the load handling apparatus showing a lifting device gripping a container from above. [Diagram 5] 5(a) and 5(b) are schematic perspective cutaway views of the load handling apparatus of FIG. 4, showing (a) a container accommodated within the container receiving space of the load handling apparatus, and (b) the container receiving space of the load handling apparatus. [Figure 6] FIG. 6 is a perspective view of an example of a known container lifting mechanism. [Figure 7] FIG. 7 is a side perspective view of a known container gripping assembly. [Figure 8] FIG. 8 is a bottom perspective view of a known container gripping assembly. [Figure 9] 9(a and b) are perspective views of another example of a known lift drive assembly for a gripper assembly, from (a) a top view and (b) a side view. [Figure 10] 10(a and b) are perspective views of a lifting drive assembly for a container gripping assembly from (a) a top view and (b) a side view, according to one embodiment of the present invention. [Figure 11] 11(a and b) are perspective views of a lifting drive assembly for a container gripping assembly according to another embodiment of the present invention, from (a) a top view and (b) a side view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present invention builds upon known features of storage systems, such as the grid framework structure and load handling apparatus described above with reference to Figures 1-5.

[0028] FIG. 6 shows a container lifting mechanism 50 known in the art, comprising a container gripping assembly 39, also known as a grabber device, for releasably connecting to an underlying storage container 10, and a lifting drive assembly 52 for raising and lowering the grabber device 39. For the avoidance of doubt, the terms "lifting drive assembly" and "container lifting assembly" are used interchangeably in this patent specification to refer to the same feature. To raise and lower the container gripping assembly 39, the lifting drive assembly known in the art comprises a set of lifting tapes or bands 38 that extend vertically between the container gripping assembly 39 and the lifting drive assembly 52. ​​For maximum stability and load capacity, typically four lifting tapes 38 wound on separate spools 53 are shown extending between each corner of the lifting drive assembly 52 and the grabber device 39. In an exemplary embodiment of the invention, the container gripping assembly 39 is formed as a frame having four corner sections, a top side 88, and a bottom side 90 (see FIG. 7). To grip the container 10, the grabber device 39 includes four locating or guide pins 80 near or at each corner of the grabber device 39 that mate with corresponding notches or holes (not shown) formed in the four corners of the container 10. Four gripping elements 84 are located on the bottom side of the grabber device 39 (see Figures 7 and 8) for engaging the rim of the container. The locating pins 80 help to properly align the gripping elements 84 with corresponding holes or openings in the rim of the container 10.

[0029] In the particular embodiment shown in FIG. 7, each of the gripping elements 84 comprises a pair of wings (see FIG. 6) that are foldable to be receivable into a corresponding hole or opening 86 in the rim of the container, and an open or expanded configuration (see FIG. 6) having at least one dimension sized larger than the hole 86 in the rim of the container to lock onto the container. The wings are actuated into the open and closed configurations by a suitable actuation mechanism coupled to a drive gear, although other actuation mechanisms for actuating gripping elements known in the art are applicable in the present invention. In the particular example shown in FIG. 7, the head of at least one of the wings comprises a number of teeth that mesh with the drive gear, such that when the gripping elements 84 are actuated by the actuation mechanism, rotation of the drive gear rotates the pair of wings from the folded configuration to the open and expanded configuration (see FIGS. 7 and 8). When in the folded or closed configuration, the gripping elements 84 are sized to be receivable into a corresponding hole 86 in the rim of the container, as shown in FIG. 6. Each leg of the pair of wings is provided with a stop 89, e.g. a boss, so that when received in a corresponding hole 86 in the rim of a container, the stop 89 engages the underside of the rim when in the expanded open configuration and locks onto the container as the grabber apparatus 39 is rolled upwardly towards the container receiving portion of the load handling apparatus.

[0030] 6 also shows that the four lifting tapes 38 are wound on separate spools or reels 53 and driven in rotational motion by a lifting drive mechanism or drive assembly 52 that includes a separate drive motor 54 for raising and lowering the grabber device 39. The lifting tapes 38 are wound in multiple layers on their respective spools 53. To ensure that the lifting tape 38 overlaps or wraps on itself as it is wound onto the spools 53, opposing ends of the spools 53 include flanges 56 for restraining the lifting tape 38 on the spools 53. The width of the spool between the flanges is approximately the width of the lifting tape.

[0031] The drive motors 54 are typically brushless DC electric motors. The separate drive motors 54 are driven synchronously to provide synchronous rotational movement of all spools 52. This helps to keep the container gripping assembly 39 level during operation so as to allow the container gripping assembly, particularly the gripping elements 84, to properly engage with the storage container 10. To reduce the cost of having separate drive motors to drive the rotation of the spools, a single motor has recently been used in the art to drive the rotation of the separate spools to raise and lower the container gripping assembly, based on having a pulley system connected to a single motor by one or more timing belts, as described in WO2021 / 148657 (Ocado Innovation Limited) and shown in Figures 9(a and b).

[0032] In the illustrated embodiment of a container lifting mechanism 151 described in WO2021 / 148657 (Ocado Innovation Limited) and shown in Figures 9(a and b), the lifting drive assembly 151 comprises a single motor 152, a drive pulley 153 attached to a drive shaft of the single motor 152, a first timing pulley 155 and a second timing pulley 161. The first timing pulley 155 is positioned between the drive pulley 153 and the second timing pulley 161. The drive pulley 153 is connected to the first timing pulley 155 and the second timing pulley 161 by a single timing belt 154 that extends around the drive pulley 153 and the first and second timing pulleys 155 and 161 such that an upper portion of the single timing belt 154 assumes a serpentine shape. In a particular embodiment of the invention, the single timing belt 154 includes a plurality of teeth that engage corresponding teeth on the first and second timing pulleys 155, 161. Thus, rotation of the drive pulley 153 by the single motor 152 causes corresponding rotation of the first and second timing pulleys 155, 161. Because the first and second timing pulleys 155, 161 are in contact with the inner surface of the single belt 154, the first and second timing pulleys 155, 161 each rotate in the same direction. The plurality of spools 157, 162, 167, 168 carrying the lifting tethers includes a first set of spools 157, 162 including the first spool 157 and the second spool 162, and a second set of spools 167, 168 including the third spool 167 and the fourth spool 168. The lifting tether 38 wound on a first set of spools is secured to one side of the container gripping assembly 39 and the lifting tether 38 wound on a second set of spools 167, 168 is secured to the other side of the container gripping assembly 39. In the embodiment shown in Figure 9a, the first set of spools 157, 162 are mounted on a lifting shaft 170 common to the first timing pulley 155 such that the first set of spools 157, 162 rotate with the first timing pulley 155.Compared to the first set of spools 157, 162, the second set of spools 167, 168 are each mounted on a separate shaft. The second timing pulley 161 is mounted on the same shaft as the third spool 167 such that the third spool 167 is connected for rotation with the second timing pulley 161 by a single timing belt 154. To drive the rotation of the fourth spool 168 of the second set of spools, the third timing pulley 163 is mounted for rotation on a lifting shaft 170 carrying the first set of spools 157, 162, and the fourth spool 168 is connected for rotation with the single shaft 170 by a second timing belt 164 around the third timing pulley 163 and the fourth timing pulley 165. The fourth timing pulley 165 is connected for rotation with the fourth spool 168. Thus, rotation of the drive pulley 153 by the single motor 152 synchronously drives rotation of the first set of spools 157, 162 and the second set of spools 167, 168 to raise and lower the container gripping assembly 39. The first and second timing pulleys 155, 161 are positioned in contact with the inner surface of the timing belt 154 such that the plurality of timing pulleys (first and second) 155, 161 rotate in the same rotational sense as the drive pulley 154. In the embodiment shown in Figure 9a, counterclockwise rotation of the first set of spools 157, 162 and the second set of spools 167, 168 raises the container gripping assembly and clockwise rotation of the drive pulley 153 lowers the container gripping assembly. The first set of spools 157, 162 and the second set of spools 167, 168 are connected to their respective timing pulleys, i.e., first timing pulley 155, second timing pulley 163, third timing pulley 161 and fourth timing pulley 165, such that the timing belt causes the timing pulleys and the first and second sets of spools to rotate synchronously. In the embodiment shown in Figure 9a, the spools are connected to rotate with their respective timing pulleys by one or more bolts.

[0033] The single timing belt 154 around the drive pulley 153, the first timing pulley 155 and the second timing pulley 161 is tensioned by a belt tensioning wheel 166a configured to urge the timing belt 154 against the first timing pulley 155. The belt tensioning wheel 166a presses against the outer surface of the timing belt 154 such that a section of the timing belt is formed into a serpentine shape. This increases the wrap angle of the timing belt 154 about the first timing pulley 155, thereby reducing the risk of the timing belt slipping on the first timing pulley 155. A similar belt tensioning wheel 166b for a similar purpose is provided to urge the second timing belt 164 against the third timing pulley 163, thus increasing the wrap angle on the third timing pulley 163.

[0034] While the use of belt tensioning wheels 166a, 166b increases the wrap angle of the timing belt on the timing pulleys, an arrangement of multiple timing pulleys connected by a single timing belt still suffers from belt slip on one or more of the timing pulleys. In a particular embodiment of the invention, slip of the belt on one or more of the timing pulleys involves slip of one or more teeth of the belt on one or more of the timing pulleys. One hypothesis of why the timing belt slips on the timing pulleys even when belt tensioning wheels 166a, 166b are used to increase the wrap angle of the timing belt on the timing pulleys is related to the amount of tension the timing belts 154, 164 are under when the torque of a single motor, which can be as much as 120 Nm, is transmitted to the single belt 154. Applying the principle of Hooke's Law, a timing belt is under strain (strain = elongation / length) when it is under applied tension. The greater the applied tension, the greater the stretch of the timing belt and therefore the greater the strain on the timing belt. Considering that the applied tension is greatest when lifting a fully loaded storage container, which can weigh as much as 35 kg, the strain on the timing belt is greatest when raising the container gripping assembly than when lowering a storage container that is under high tension under gravity. In accordance with the present invention, controlling the amount of the timing belt under applied tension and redistributing the applied tension to a smaller section of the timing belt when raising the container gripping assembly will reduce the amount of strain experienced by the timing belt and therefore the stretch of the belt.

[0035] According to the present invention, the amount of timing belt under tension can be controlled by the position of the belt tensioning wheel in the pulley system. Taking the example of a single belt and belt tensioning wheel 166a arrangement shown in FIG. 9b of WO2021 / 148657 (Ocado Innovation Limited), the belt tensioning wheel 166a is positioned to urge the timing belt 154 against the top of the first timing pulley 155 such that a section of the timing belt assumes a serpentine shape above the first timing pulley. When raising the container gripping assembly, the direction of rotation of the spool is counterclockwise, so the load path T1 from the single motor to the first pulley is via the second pulley 161, as shown by the arrow in FIG. 9b. The arrows in Figure 9b show the direction of the load path T1 as the single motor 152 attempts to pull a longer section of the timing belt 154 in an endless loop from the first timing pulley 155 through the second timing pulley 161 towards the drive pulley 153 when raising the container gripping assembly. Due to the position of the belt tensioning wheel 166a biasing the timing belt 154 against the top side of the first pulley 155, the tension in the second section of the timing belt 154 (shown as T2 in Figure 9b) between the drive pulley 153 and the first pulley 155 moving away from the drive pulley 153 is less than the tension in the section T1 of the timing belt moving from the first timing pulley 155 through the second timing pulley 161 towards the drive pulley 153. For ease of explanation, the section of the timing belt that is under maximum tension when raising the container gripping assembly 39 is the first section of the timing belt and the timing belt between the first and second timing pulleys is the second section. Since the section of the timing belt that is under maximum tension when raising the container gripping assembly 39 is the distance from the drive pulley 153 through the second pulley 161 to the first pulley 155, this section is considered to be the first section of the timing belt 154, indicated by T1 in FIG. 9b.A second section of the timing belt, which is much smaller than the first section, is between the drive pulley 153 and the first pulley 155, indicated by arrow T2 in Figure 9b. Note that the timing belt moves towards the drive pulley 153 in the first section of the timing belt and moves away from the drive pulley 153 in the second section of the timing belt.

[0036] As a result, a longer length of the timing belt is under the applied tension, which results in the first section of the timing belt, which extends from the first pulley 155 through the second pulley 161 to the drive pulley 153, being placed under increased strain. Depending on the material properties of the timing belt, which may be rubber or chain, the increased strain in the first section of the timing belt as a result of the stretching of the timing belt will introduce some slack into the timing belt, especially when the container gripping assembly is being raised upward. The amount of slack in the timing belt determines the level of slip of the timing belt on one or more timing pulleys, especially the first timing pulley 155, i.e., the timing belt misses one or more teeth on the first timing pulley 155. As more of the timing belt 154 stretches, the level of slack in the timing belt increases. Slippage of the timing belt 154 on the first timing pulley 155 causes the rotation of the first set of spools 157, 162 attached to the shaft 170 carrying the first pulley 155 to become out of sync with the rotation of the second set of spools 167, 168, with the result that the container gripping assembly secured to the lifting tether will become uneven because there will be periods in the rotation of the multiple timing pulleys where the timing pulleys do not rotate in sync.

[0037] An obvious solution would be to provide a much stronger timing belt to reduce the amount of slack on the timing belt when under applied tension when the single motor applies a torque in one rotational direction that can be as high as 120 Nm. However, such a solution would be expensive and would require a thicker timing belt, which is not practical given the limited available space in the container lifting mechanism. Even if the single motor were to incorporate a motor brake slip that would allow the shaft 170 of the single motor to slip when the torque of the single motor exceeds a predetermined level, the belt strain would typically exceed a predetermined level before the motor brake slip takes effect, resulting in belt slippage. For example, a torque of 62 Nm may be required to raise the container gripping assembly, and the motor brake slip takes effect when the torque on the single motor exceeds 120 Nm. In the arrangement shown in Figures 9(a and b), when the torque on the single motor in raising the container gripping assembly reaches 62 Nm, the timing belt would slip rather than the motor brake slip taking effect. Ideally, the lift drive assembly should be constructed so that the motor brake slip takes effect prior to any slippage of the timing belt on the timing pulleys.

[0038] According to an embodiment of the present invention, the position of the belt tensioning wheel 266a can be used to redistribute tension to a smaller section of the timing belt. According to the present invention, the load path from the first timing pulley 255 towards the drive pulley 253 is minimized when lifting the container gripping assembly, thereby reducing the strain on the timing belt 254. Based on the same rotational direction of the first and second sets of spools for lifting the container gripping assembly shown in Figures 9(a and b), i.e., counterclockwise direction, in one embodiment of the container lifting mechanism 251 according to the present invention as shown in Figures 10(a and b), the belt tensioning wheel 266a is repositioned to urge the timing belt 254 against the underside of the first pulley 255 so that the timing belt 254 assumes a serpentine shape under the first pulley 255. 10b, is minimized because the length of the section of the timing belt from the first pulley 255 to the drive pulley 253 or the single motor 252 (defined herein as the first section T1) is much shorter than the length of the section of the timing belt 254 from the drive pulley 253 to the first pulley 255 via the second pulley 261 (defined herein as the second section T2). With the smaller section of the timing belt under increased tension compared to the remainder of the timing belt 254, the degree of strain applied to this first section of the timing belt is minimized, thereby minimizing any stretching of the timing belt when raising the container gripping assembly, reducing slack in the timing belt and therefore reducing slippage of the timing belt on the first timing pulley 255 or the second timing pulley 261. Lower tension in the timing belt occurs as it leaves drive pulley 253 and passes through second timing pulley 261 to first timing pulley 255 (see load path T2 in FIG. 10b).Since there is a smaller wrap angle of the timing belt 254 around the first pulley 255 compared to the second pulley 261, any slippage of the timing belt as a result of slippage of one or more teeth on the first pulley is more likely to occur on the first pulley 255. In the particular embodiment of the invention shown in Figures 10(a and b), when the rotation direction of the first timing pulley 255 and the second timing pulley 261 for raising the container gripping assembly is in a counterclockwise direction, the tension applied in the first section T1 of the timing belt between the drive pulley 253 and the first timing pulley 255 is greater than the tension applied in any segment of the second section T2 of the timing belt 254 between the first timing pulley 255 and the drive pulley 253 via the second timing pulley 261. Since the length of the first section T1 of the timing belt 254 is less than the length of the second section T2 of the timing belt, according to Hooke's law, the level of elongation of the first section T1 of the timing belt is less than when the second section T2 of the timing belt is under increased tension as shown in Fig. 9(a and b). Applying increased tension to a larger section of the belt, in this case T2 as shown in Fig. 10(a and b), increases the level of slack built into the belt, thereby increasing the risk of slipping on one or more of the timing pulleys. This reduced elongation results in minimal slack in the timing belt, thus reducing the possibility of slipping of the timing belt on the first pulley 255. In other words, the first section T1 of the timing belt between the drive pulley 253 and the first pulley 255 experiences a greater tension when the timing belt 254 is pulled towards the drive pulley 253, resulting in strain on the first section of the timing belt as a result of the single motor lifting the container gripping assembly. Because the length of this section of the timing belt is shorter, any stretch in this section of the timing belt is minimal, causing little or no slippage of the belt on the first timing pulley 255 .Although not explicitly shown in Fig. 10a, the above-mentioned redistribution of timing belt tension by the belt tensioning wheel over a smaller section of the timing belt also applies to the second timing belt 264 on the third timing pulley 263. Due to the increased wrap angle of the timing belt around the second timing pulley 261 and / or the fact that the force when lowering the container gripping assembly is mainly gravity, there is less of an issue with the belt slipping when lowering the container gripping assembly. Furthermore, because the wrap angle of the timing belt 254 on the second pulley 261 is larger, the risk of the timing belt 254 slipping on the second pulley 261 is significantly reduced.

[0039] The present invention is not limited to the rotation direction being counterclockwise when lifting the container gripping assembly, but can also be applied when the rotation direction of the single motor is clockwise when lifting the container gripping assembly. In a second example of a container lifting mechanism 351 according to the present invention shown in Fig. 11 (a and b), clockwise rotation of the single motor 352 lifts the container gripping assembly (not shown) and counterclockwise rotation lowers the container gripping assembly. A common arrangement in both examples of the present invention is to control the tension in a section of the timing belt that is pulled towards the drive pulley. Since the rotation direction is clockwise when lifting the container gripping assembly, the first section T1 of the timing belt 354 that experiences increased tension in the timing belt when lifting the container gripping assembly is above the first pulley 355, since in this region there is an initial pull of the timing belt towards the drive pulley 353. As a result, the belt tensioning wheel 366a is repositioned so that the timing belt 354 is urged above the first timing pulley 355, which repositions the maximum tension of the timing belt between the drive pulley 353 and the first timing pulley 355, i.e., the first section T1 of the timing belt. The second section T2 of the timing belt is between the first timing pulley 355 and the drive pulley 353 via the second pulley 361. The second section of the timing belt experiences maximum tension when lowering the container gripping assembly, which is a counterclockwise rotation. The reduced tension of the second (longer) section T2 of the timing belt when raising the container gripping assembly reduces any strain on the first (shorter) section of the timing belt. Because the force on the timing belt when lowering the container gripping assembly is primarily due to gravity, the tension in the second section of the timing belt is not great enough to cause the belt to slip on the second pulley.Furthermore, since there is a larger wrap angle of the timing belt around the second pulley 361, the risk of slipping of the timing belt around the second pulley 361 is greatly reduced. The position of the belt tensioning wheel 266a is similar to the arrangement in the art as shown in Figures 9(a and b), but the direction of rotation of the single motor is reversed when raising and lowering the container gripping assembly so that the first section of the timing belt is between the drive pulley 353 and the first pulley 355.

[0040] The diameter of the timing pulleys in the pulley systems in both embodiments of the invention shown in Figures 10(a & b) and 11(a & b) are the same as the timing pulleys shown in Figures 9(a & b), and as a result, the variations in tension in the timing belt all result from the different placement of the timing pulleys. The inventive concept of the invention shown in Figures 10(a & b) and 11(a & b) is the distribution of the timing belt tension towards the shorter segment of the timing belt that is pulled towards the drive pulley when lifting the container gripping assembly.

Claims

1. 1. A robotic load handling device for lifting and moving containers stacked in a stack on a grid framework structure, the grid framework structure including a first set of tracks extending in a first direction above the stack of containers and a second set of tracks extending in a second direction transverse to the first direction, the load handling device configured to move on the tracks above the stack, the load handling device: a wheel assembly comprising a first set of wheels for engaging the first set of tracks to guide movement of the load handling apparatus in the first direction and a second set of wheels for engaging the second set of tracks to guide movement of the load handling apparatus in the second direction; a wheel positioning mechanism for selectively engaging either the first set of wheels with the first set of tracks or the second set of wheels with the second set of tracks, wherein the wheel positioning mechanism is configured to raise or lower the first set of wheels or the second set of wheels relative to a body, thereby enabling the load handling apparatus to selectively move in either the first direction or the second direction across the tracks of the grid framework structure; a container lifting mechanism comprising a container gripping assembly configured to releasably grip a container, and a lifting drive assembly configured to raise and lower the container gripping assembly; the lifting drive assembly including a single motor configured to raise the container gripping assembly in a first rotational direction and to lower the container gripping assembly in a second rotational direction; a first set of spools and a second set of spools, where each spool of the first and second sets of spools carries a lifting tether having a first end secured to the container gripping assembly and a second end secured to its respective spool; a drive pulley connected for rotation with the single motor; a plurality of timing pulleys connected for rotation with the first and second sets of spools and the drive pulley, such that the single motor is configured to rotate the first and second sets of spools to raise and lower the container gripping assembly; the plurality of timing pulleys comprises a first timing pulley and a second timing pulley, the first and second timing pulleys being rotationally connected to the drive pulley by a single timing belt forming a closed loop around the first and second timing pulleys and the drive pulley such that the drive pulley drives the rotation of the first and second timing pulleys in the same rotational sense; 11. A robotic load handling apparatus comprising: a lift drive assembly including a first timing pulley and a second timing pulley; and a belt tensioning wheel disposed between the first timing pulley and the second timing pulley, the belt tensioning wheel being arranged to urge the single timing belt against the first timing pulley such that a tension in a first section of the single timing belt between the first timing pulley and the drive pulley, the first section moving in a direction toward the drive pulley when the single motor rotates in the first rotational direction, is greater than a tension in a second section of the single timing belt between the first timing pulley and the second timing pulley.

2. 2. The robotic load handling device of claim 1, wherein a length of the first section of the single timing belt is less than a length of the second section of the single timing belt.

3. 3. The robotic load handling apparatus of claim 1, wherein the belt tensioning wheel is positioned to urge the single timing belt against an underside of the first timing pulley when the first rotational direction is a counterclockwise direction and the second rotational direction is a clockwise direction.

4. 3. The robotic load handling apparatus of claim 1, wherein the belt tensioning wheel is positioned to urge the single timing belt against an upper side of the first timing pulley when the first rotational direction is a clockwise direction and the second rotational direction is a counterclockwise direction.

5. 5. The robotic load handling apparatus of claim 1, wherein the first timing pulley and the first set of spools are mounted for rotation on a lifting shaft such that the lifting shaft is common to the first set of spools and the first timing pulley.

6. 6. The robotic load handling device of claim 5, wherein at least one of the second set of spools is connected to the shaft by a second timing belt thereby being driven by the single motor.

7. 7. The robotic load handling apparatus of claim 6, wherein the lift drive assembly further comprises a third pulley rotatably mounted on the lift shaft and a fourth pulley rotatably connected to the at least one of the second set of spools, the second timing belt forming a closed loop around the third and fourth pulleys such that a lift shaft drives rotation of the at least one of the second set of spools.

8. 8. The robotic load handling apparatus of claim 7, wherein the lifting drive assembly further comprises a second belt tensioning wheel positioned to urge a second belt against the third pulley.

9. 6. The robotic load handling apparatus of claim 5, wherein the lifting drive assembly further comprises a second lifting shaft defining a first lifting shaft, the second lifting shaft being substantially parallel to the first lifting shaft, the second set of spools and second timing pulleys being mounted for rotation on the second lifting shaft, the second lifting shaft being connected to the first lifting shaft by the single timing belt such that it is rotated by the single motor.

10. The robotic load handling apparatus of any one of claims 1 to 9, wherein the belt tensioning wheel is adjustable to adjust the force of the single timing belt on the first timing pulley.

11. 11. The robotic load handling apparatus of claim 1, wherein the container lifting mechanism comprises a communications spool carrying a communications cable for sending and / or receiving communication signals to and from the container gripping assembly, the communications cable having a first end connected to the communications spool and a second end connected to the container gripping assembly, the communications spool being rotatably mounted on the lifting shaft such that a single motor is configured to raise and lower the second end of the communications cable together with the container gripping assembly.

12. 12. The robotic load handling apparatus of claim 1, further comprising a vehicle body having an upper portion and a lower portion, the upper portion configured to house one or more operating components, the lower portion being disposed below the upper portion, the lower portion comprising a container receiving space for accommodating at least a portion of a container.

13. A robotic load handling device according to any preceding claim, wherein the single motor drives the first set of spools and the second set of spools synchronously.

14. The robotic load handling apparatus of any one of claims 1 to 13, wherein the container gripping assembly comprises a frame structure.

15. 1. A storage and retrieval system comprising: a track system comprising a first set of parallel tracks and a second set of parallel tracks arranged in a grid pattern comprising a plurality of grid spaces or grid cells; a stack of containers positioned beneath the rail system, each of the stacks of containers occupying a single grid space or grid cell; a load handling apparatus according to any one of claims 1 to 14, arranged to traverse along the track system over a plurality of grid spaces or grid cells such that when positioned above a stack of containers occupying a grid space or grid cell, the container lifting mechanism is configured to lift at least one container from the stack of containers; A grid framework structure comprising: A storage and retrieval system comprising:

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