Patent Description:
Some commercial and industrial activities require systems that enable the storage and retrieval of a large number of different products. One known type of system for the storage and retrieval of items in multiple product lines involves arranging storage containers (also known as bins or totes) in stacks on top of one another, the stacks being arranged in rows. The storage containers are removed from the stacks and accessed from above by load handling devices, removing the need for aisles between the rows and thereby allowing a large number of containers to be stored in a given space.

<CIT> describes a storage and fulfilment system in which stacks of storage containers are arranged within a grid framework structure. The containers are accessed by load handling devices operative on tracks located on the top of the grid framework structure.

The storage containers in such storage systems are typically made of a thermoplastic material and may be formed by injection moulding or blow moulding, for example. Examples of thermoplastic materials include polypropylene, polyethylene (e.g. high density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS) and polycarbonate.

<CIT> (Autostore Tech AS) teaches a service vehicle for extinguishing fire on and within an automated storage and retrieval system and a method for operating such a service vehicle. The service vehicle comprises caterpillar tracks allowing movement of the service vehicle across a rail system and a fire extinguisher compartment for containing firefighting equipment.

<CIT>) teaches a container assembly having a container body and exterior shelf structures that are each reversibly attached to exterior surfaces of first and second sidewalls of the container body.

<CIT>) teaches a method and device for the production of thermoplastics containing coarse-scale and/or nanoscale, coated, deagglomerated magnesium hydroxide particles that are supplied to the thermoplastic in the form of a dispersion or suspension in an aqueous or organic solvent, and mixed with the themoplastic. The thermoplastics filled with magnesium hydroxide particles demonstrate improved mechanical properties, particularly an improved modulus of elasticity and low brittleness.

A problem with using thermoplastic storage containers in the storage systems described above is that they can be highly flammable, and given that the storage system may contain hundreds or thousands of storage containers, the storage containers pose a significant risk in the event of a fire.

In a first aspect, the present invention provides a storage system comprising:.

In the storage system of the present invention, a large number of thermoplastic storage containers may be densely arranged within the grid structure. Due to the flammability of thermoplastic, this may present a fire risk, particularly if the storage containers are being used to store food items, which act as a source of fuel. The dense arrangement of storage containers may also hinder firefighting measures, particularly if a fire starts in a central region of the grid structure, which may not easily accessible. By using thermoplastic storage containers comprising a fire retardant agent within the grid structure, the spread of a fire within the grid structure can be slowed down to allow more time for firefighting systems to control the fire and limit damage to the rest of the storage system.

According to the invention the fire retardant agent is magnesium hydroxide and/or aluminium hydroxide. These fire retardant agents are generally considered safe when used as an additive in plastic articles that are intended to come into contact with food, and are therefore useful in storage systems intended to store food items.

The material of each storage container may comprise <NUM> to <NUM> wt% magnesium hydroxide.

The material of the invention comprises <NUM> to <NUM> wt% magnesium hydroxide. The material may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material may comprise approximately <NUM> wt% magnesium hydroxide.

The thermoplastic may comprise a polyolefin, e.g. polypropylene or polyethylene, including copolymers thereof. The thermoplastic may comprise high-density polyethylene (HDPE). The thermoplastic may be acrylonitrile butadiene styrene (ABS) or polycarbonate. The thermoplastic may be a single thermoplastic, or a blend of thermoplastics.

The material may consist essentially of thermoplastic and magnesium hydroxide. The proportion of the material that is not magnesium hydroxide may comprise <NUM> to <NUM> wt% thermoplastic. The proportion of the material that is not magnesium hydroxide may comprise <NUM> to <NUM> wt% thermoplastic. The material may consist of thermoplastic, magnesium hydroxide and <NUM> to <NUM> wt% other substances. The material may consist of thermoplastic, magnesium hydroxide and <NUM> to <NUM> wt% other substances. Such other substances may be one or more impact modifiers for improving the impact resistance of the material, or other additives. The material may comprise one or more impact modifiers. The material may comprise one or more impact modifiers up to a total of <NUM> wt%. The impact modifiers may be any known or commercially available impact modifiers. The material may comprise magnesium hydroxide in the proportions mentioned above and one or more impact modifiers up to <NUM> wt%, with the remaining portion being essentially thermoplastic.

The material may be free of any halogenated fire retardants (e.g. chlorinated or brominated fire retardants) and/or may be free of any phosphorous fire retardants.

The material is preferably food contact safe, i.e. meets the requirements of at least one regulation governing plastic materials intended to come into contact with food. For example, the material may meet the requirements of Commission Regulation (EU) No <NUM>/<NUM> of <NUM> January <NUM> and/or US FDA <NUM> CFR.

Each storage container may comprise one or more non-perforated sidewalls, i.e. the sidewalls do not comprise any apertures/cutouts extending horizontally through the sidewalls. Thus, when the storage containers are stacked, there are minimal openings between the storage containers in the stack for air to pass through. This may help to reduce the supply of oxygen to a fire, which may help to reduce the spread of the fire.

Each storage container may have been formed by injection moulding or blow moulding.

The storage system may further comprise a plurality of upright columns supporting the grid structure from below. The upright columns may be arranged to form a plurality of vertical storage locations for each stack of storage containers.

The horizontal gap between stacks of storage containers in adjacent grid cells may be at least approximately <NUM>. For example, the gap may be <NUM>, <NUM>, <NUM>, or any distance therebetween.

Each of the plurality of grid members may comprise a track or a rail. The track or the rail may be mounted to each of the plurality of grid members, or integrated with each of the plurality of grid members as a single body.

In a second aspect, the present invention provides a storage container for storing one or more items in a storage system according to the first aspect, the storage container comprising a base, at least one sidewall extending from the base, and a rim, wherein the rim defines at least one aperture for engaging with a corresponding member of a grabber device, and wherein the storage container is made of a material comprising thermoplastic and a fire retardant agent.

The fire retardant agent of the invention is magnesium hydroxide and/or aluminium hydroxide.

The material of the storage container may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material of the invention comprises <NUM> to <NUM> wt% magnesium hydroxide. The material may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material may comprise approximately <NUM> wt% magnesium hydroxide.

The storage container may have been formed by injection moulding or blow moulding.

The storage container may comprise four side walls extending from the base. The rim of the storage container may define four corners of the storage container. The rim may define four apertures, each aperture being located at or near a corner of storage container.

As shown in <FIG> and <FIG>, storage containers <NUM>, also known as bins or totes, are stacked on top of one another to form stacks <NUM>. The stacks <NUM> are arranged in a grid framework structure <NUM> in a warehousing or manufacturing environment. The grid framework is made up of a plurality of storage columns or grid columns. Each grid in the grid framework structure has at least one grid column for storage of a stack of containers. <FIG> is a schematic perspective view of the grid framework structure <NUM>, and <FIG> is a top-down view showing a stack <NUM> of containers <NUM> arranged within the framework structure <NUM>. Each container <NUM> typically holds a plurality of product items (not shown), and the product items within a container <NUM> may be identical, or may be of different product types depending on the application. Each container <NUM> may be used to store grocery items (i.e. food items), for example.

The grid framework structure <NUM> comprises a plurality of upright members or upright columns <NUM> that support horizontal members <NUM>, <NUM>. A first set of parallel horizontal grid members <NUM> is arranged perpendicularly to a second set of parallel horizontal grid members <NUM> to form a plurality of horizontal grid structures supported by the upright members <NUM>. The members <NUM>, <NUM>, <NUM> are typically manufactured from metal and typically welded or bolted together or a combination of both. The containers <NUM> are stacked between the members <NUM>, <NUM>, <NUM> of the grid framework structure <NUM>, so that the grid framework structure <NUM> guards against horizontal movement of the stacks <NUM> of containers <NUM>, and guides vertical movement of the containers <NUM>. The horizontal gap (indicated by the label "D" in <FIG>) between stacks <NUM> of containers <NUM> in adjacent grid cells may be at least approximately <NUM>. For example, the gap may be approximately <NUM>, e.g. <NUM>, <NUM>, <NUM>, or any distance therebetween.

The top level of the grid framework structure <NUM> includes rails <NUM> arranged in a grid pattern across the top of the stacks <NUM>. Referring additionally to <FIG>, the rails <NUM> support a plurality of load handling devices <NUM>. A first set 22a of parallel rails <NUM> guide movement of the robotic load handling devices <NUM> in a first direction (for example, an X-direction) across the top of the grid framework structure <NUM>, and a second set 22b of parallel rails <NUM>, arranged perpendicular to the first set 22a, guide movement of the load handling devices <NUM> in a second direction (for example, a Y-direction), perpendicular to the first direction. In this way, the rails <NUM> allow movement of the robotic load handling devices <NUM> laterally in two dimensions in the horizontal X-Y plane, so that a load handling device <NUM> can be moved into position above any of the stacks <NUM>.

A known load handling device <NUM> shown in <FIG> and <FIG> comprises a vehicle body <NUM> and is described in <CIT>, hereby incorporated by reference, where each load handling device <NUM> only covers one grid space of the grid framework structure <NUM>. Here, the load handling device <NUM> comprises a wheel assembly comprising a first set of wheels <NUM> comprising a pair of wheels on the front of the vehicle body <NUM> and a pair of wheels <NUM> on the back of the vehicle <NUM> for engaging with the first set of rails or tracks to guide movement of the device in a first direction and a second set of wheels <NUM> comprising a pair of wheels <NUM> on each side of the vehicle <NUM> for engaging with the second set of rails or tracks to guide movement of the device in a second direction. Each of the set of wheels are driven to enable movement of the vehicle in X and Y directions respectively along the rails. One or both sets of wheels can be moved vertically to lift each set of wheels clear of the respective rails, thereby allowing the vehicle to move in the desired direction.

The load handling device <NUM> is equipped with a lifting device or crane mechanism to lift a storage container <NUM> from above. The crane mechanism comprises a winch tether or cable <NUM> wound on a spool or reel (not shown) and a grabber device <NUM>. The lifting device comprises a set of lifting tethers <NUM> extending in a vertical direction and connected nearby or at the four corners of the grabber device <NUM> (one tether near each of the four corners of the grabber device) for releasable connection to a storage container <NUM>. The grabber device <NUM> is configured to releasably grip the top of a storage container <NUM> to lift it from a stack <NUM> of containers in a storage system of the type shown in <FIG> and <FIG>.

The wheels <NUM>, <NUM> are arranged around the periphery of a cavity or recess, known as a container-receiving recess <NUM>, in the lower part. The recess is sized to accommodate the container <NUM> when it is lifted by the crane mechanism, as shown in <FIG>. When in the recess, the container is lifted clear of the rails beneath, so that the vehicle can move laterally to a different location. On reaching the target location, e.g. another stack, an access point in the storage system or a conveyor belt, the container can be lowered from the container receiving portion and released from the grabber device.

In the particular embodiment shown in <FIG>, the grabber device <NUM> comprises four locating pins or guide pins <NUM> nearby or at each corner of the grabber device <NUM> which mate or engage with corresponding holes or apertures <NUM> formed at four corners of the container <NUM>. Four gripper elements (not shown) arranged at the bottom side of the grabber device <NUM> engage with the rim of the container. The locating pins <NUM> help to properly align the gripper elements with the rim of the container. The gripper elements may be driven to engage with the storage container <NUM> by a suitable drive mechanism housed within the grabber device <NUM>, which is powered and controlled by signals carried through the tethers <NUM> themselves or through a separate control cable (not shown).

<FIG> shows a perspective view of an example storage container 10a that may be stored in a stack within the grid framework structure <NUM>. The storage container 10a has a substantially rectangular base <NUM> with four sidewalls 104a extending from the base to form an open-topped container. The sidewalls 104a are "vented" in that they comprise apertures <NUM> extending horizontally through the sidewalls 104a. The apertures <NUM> allow for ventilation and air circulation through the storage containers 10b when stacked, which may be useful when storing certain items and when the items in the storage containers 10b need to be held at a certain temperature in a temperature controlled environment (e.g. for chilled food items). The sidewalls 104a also comprise apertures <NUM> extending horizontally through the sidewalls 104a which act as handles and apertures/cutouts <NUM> which extending horizontally through the sidewalls 104a which allow other containers to be inserted into and removed from the storage container 10a more easily. The storage container 10b further comprises an overhanging rim <NUM> that forms the top surface of the storage container. The rim <NUM> comprises vertically extending apertures <NUM> for receiving gripping members of the grabber device <NUM> to allow the load handling device <NUM> to grab and lift the storage container 10a. The rim <NUM> further comprises four vertically extending apertures/cutouts <NUM> formed at the four corners of the container, which receive the locating pins <NUM> of the grabber device <NUM> to help locate the grabber device <NUM> into the correct position to align the gripping members with the apertures <NUM>.

<FIG> shows a perspective view of another example of a storage container 10b that may be stored in a stack within the grid framework structure <NUM>. The storage container 10b is similar to storage container 10a in all respects (including its shape and the features of the rim <NUM>), except that the sidewalls 104b are "solid". In particular, the sidewalls 104b do not comprise any apertures/cutouts extending horizontally through the sidewalls <NUM> (such as the apertures <NUM>, <NUM> and <NUM> of storage container 10a). The sidewalls <NUM> may also be described as non-perforated. Due to the solid sidewalls <NUM>, a stack of storage containers 10b will not have any significant openings for air to pass between the storage containers 10b in the stack.

It is desirable for the storage container <NUM> to be flame retardant, especially in a warehouse environment containing the gird structure framework <NUM> of <FIG>, where there may be hundreds or thousands of storage containers stacked within the structure.

In the present invention, the storage container <NUM> is made of a material comprising thermoplastic and a fire retardant.

The thermoplastic component of the material may be a polyolefin. For example, the thermoplastic may comprise polypropylene or polyethylene (e.g. HDPE), including copolymers thereof (or other polyolefin copolymers). The thermoplastic may comprise polycarbonate or acrylonitrile butadiene styrene (ABS). The thermoplastic component may be a single thermoplastic, or may comprise a blend of two or more thermoplastics, such as a blend of polypropylene and HDPE.

The fire retardant component of the material may be magnesium hydroxide, Mg(OH)<NUM>. When heated, magnesium hydroxide undergoes endothermic decomposition and releases water vapour, thereby acting as a fire retardant. Magnesium hydroxide is also considered non-toxic, which is desirable because the storage container <NUM> may be used to store grocery items (i.e. food items) in use. Magnesium hydroxide is generally allowed by many national and supranational regulations to be present as an additive in plastic articles that are intended to come into contact with food, e.g. Commission Regulation (EU) No <NUM>/<NUM> of <NUM> January <NUM> on plastic materials and articles intended to come into contact with food.

On the other hand, introducing magnesium hydroxide into the thermoplastic material of the storage container <NUM> may have a detrimental effect on some of the mechanical properties of the storage container. In use, the storage container <NUM> may be located in a stack <NUM> of storage containers within the grid framework structure <NUM> and therefore it is desirable for each storage container <NUM> to be mechanically strong enough to support the weight of multiple containers above it. Furthermore, it is desirable for each storage container <NUM> to have small dimensional tolerances because the grabber device <NUM> of the load handling device <NUM> needs to be able to precisely engage with corresponding elements of the storage container <NUM> (e.g. apertures <NUM>) in order to grab and lift each storage container <NUM> in a repeatable and reliable manner.

It is therefore desirable that the material of the storage container <NUM> gives the storage container <NUM> fire retardant properties while still maintaining physical properties that are adequate for the storage container <NUM> to be used in the storage system.

The material of the storage container <NUM> may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material of the storage container <NUM> may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material of the storage container <NUM> may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material of the storage container <NUM> may comprise <NUM> to <NUM> wt% magnesium hydroxide. The material of the storage container <NUM> may comprise approximately <NUM> wt% magnesium hydroxide.

The remaining proportion of the material is preferably essentially thermoplastic. Put another way, the material of storage container <NUM> preferably consists essentially of thermoplastic and magnesium hydroxide. The use of the word "essentially" means that other substances may be present in trace or small amounts (e.g. less than or equal to <NUM> wt%, or less than or equal to <NUM> wt%), which may be a result of additives or impurities from the manufacturing process.

To increase mouldability and impact resistance of the storage containers, one or more impact modifiers may be added to the material before or during manufacture of the storage container in order to increase the impact resistance of the final product. Other known additives may be added to increase the mouldability of the material for manufacture, for example. The material may comprise one or more impact modifiers up to a total of <NUM> wt%. Any known or commercially available impact modifiers (e.g. core/shell impact modifiers having a rubber core and polymer shell) may be used to give the desired properties of the storage container. The impact modifiers are preferably food contact safe.

The material of the storage container <NUM> is preferably free of any halogenated fire retardants (e.g. chlorinated or brominated fire retardants) and/or phosphorous fire retardants, as at least some of these substances may be considered toxic and not suitable for contacting food items.

The storage container <NUM> may be formed by known manufacturing processes for moulding plastic articles, such as injection moulding or blow moulding.

The feedstock for the moulding process may be formed by incorporating the fire retardant agent (e.g. magnesium hydroxide) into the thermoplastic using conventional techniques, e.g. using a mixer, blender or extruder (single screw or twin screw). As mentioned above, commercially available impact modifiers may be added to the material in order to increase mouldability of the material and the impact resistance of the final product.

The magnesium hydroxide particles may be in the form of surface coated particles to aid dispersion of the particles in the thermoplastic. An example surface coating is vinyltrimethoxy silane.

As an alternative to magnesium hydroxide, aluminium hydroxide may be used in the storage container material in the same or similar weight percentages to the weight percentages specified above for magnesium hydroxide. Alternatively, a mixture of magnesium hydroxide and aluminium hydroxide may be used with overall weight percentages that are the same or similar to the weight percentages specified above for magnesium hydroxide.

Example polypropylene material samples containing varying proportions of magnesium hydroxide were manufactured using an injection moulding process for cone calorimeter testing. The proportions of magnesium hydroxide tested were: <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt% and <NUM> wt%.

Fire testing of each example sample was carried out using a cone calorimeter test according to the ASTM E1354 test method using a heat flux of <NUM> kW/m<NUM>. As a comparative example, an injection-moulded polypropylene sample comprising no (i.e. <NUM>%) magnesium hydroxide was also tested. The rate of heat release over time for each sample is shown in the graph of <FIG>.

As <FIG> shows, the addition of magnesium hydroxide at a proportion of at least <NUM> wt% decreased the heat release rate by approximately <NUM>% compared to the comparative example containing no magnesium hydroxide. The heat release rate lowered as the proportion of magnesium hydroxide increased, but there were diminishing returns as the proportion of magnesium hydroxide increased above about <NUM> wt%.

The mechanical properties of injection moulded samples containing varying proportions of magnesium hydroxide were also tested. The injection moulding feedstock was a mix of polypropylene and magnesium hydroxide. The proportions of magnesium hydroxide tested were: <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt% and <NUM> wt%. To improve mouldability and toughness of the material, one or more impact modifiers totalling <NUM> wt% were included in the material for the samples containing <NUM> wt% and above magnesium hydroxide.

The mechanical tests carried out for each sample were: shore hardness using the ASTM D2240 test method (type D with a <NUM> second delay); specific gravity using the ASTM D792 test method; tensile strength using the ASTM D412A test method; flexural modulus using the ASTM D790 test method and Izod impact test using the ASTM D4812 test method.

The results are summarised in Table <NUM>. Table <NUM> also shows some mechanical property data from the polypropylene material containing no magnesium hydroxide as a comparative example.

Polypropylene storage containers containing varying proportions of magnesium hydroxide were manufactured using an injection moulding process. Polypropylene storage containers containing the following proportions of magnesium hydroxide were formed: <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt%, <NUM> wt% and <NUM> wt%. To improve mouldability and toughness of the materials containing <NUM> wt% and above magnesium hydroxide, one or more impact modifiers totalling <NUM> wt% were included in the material feedstock. The storage containers were approximately <NUM> in length, <NUM> in width, <NUM> in height and <NUM> in thickness.

In a first set of tests, three storage containers were arranged in a vertical stack and ignited to observe the behaviour of the resulting fire. Separate tests were carried out for polypropylene storage containers containing <NUM> wt%, <NUM> wt%, and <NUM> wt% magnesium hydroxide. It was observed that the stacks of storage containers containing magnesium hydroxide had the following advantageous effects compared to the stack of storage containers containing no magnesium hydroxide: (i) the stack retained its structural integrity (i.e. remained upright) for longer; (ii) a longer amount of time passed before the burning storage container material started melting/dripping; and (iii) the fire did not spread horizontally when the stacks were quenched with water.

A second set of tests were carried out on grid framework structures loaded with multiple stacks of storage containers to see how effective the storage containers were at preventing or slowing the spread of a fire within the grid framework structure.

Claim 1:
A storage system comprising:
a plurality of grid members (<NUM>, <NUM>) arranged in a grid pattern to form a grid structure comprising a plurality of grid cells;
one or more stacks of storage containers (<NUM>), wherein each stack is located vertically below a respective grid cell, and each storage container (<NUM>) in each stack is made of a material comprising thermoplastic and a fire retardant agent; and
at least one load handling device (<NUM>) comprising a grabber device (<NUM>) operative to move on the grid structure to releasably grab one or more of the storage containers from each stack in the storage system;
characterised in that the material comprises <NUM> to <NUM> wt% magnesium hydroxide.