Transfer mechanism, system, and method

Abstract

A transfer mechanism, system and method are provided for transferring one or more items between a first region and a second region. The first region is enclosed and maintained at a first environmental

Description

Technical Field The disclosure relates to a transfer mechanism, system, and method for transferring items between a first region and a second region at different environmental conditions. For example, the transfer mechanism may transfer items from the first region at a frozen temperature to the second region at a chilled or ambient temperature, for picking and packing of the items for fulfilling customer orders. The transfer mechanism may be provided as part of a customer fulfilment centre. Background Fulfilment of customer orders can include items at different temperatures, for example grocery orders with ambient, chilled, and frozen goods. While storage and retrieval systems are commonly deployed for the storage and retrieval of ambient food items and chilled food items, there are challenges associated with the automated storage and retrieval of frozen food items, which require lower temperatures than ambient and chilled goods for safe storage. For example, a freezer section within a wider storage and retrieval system needs to be separated from other sections of the system that are operating in different environments, in order to maintain the appropriate environmental conditions. Picking customer orders in certain environmental conditions (for example, low temperatures) is problematic. There are issues relating to comfort and health and safety of human workers when working at freezing temperatures. Machinery is generally not rated to low temperatures, and providing machinery that can operate in harsh environmental conditions may require bespoke parts that are more expensive. It is therefore desirable to provide a storage and retrieval system for storing and retrieving items in different environmental conditions, that enables transfer of items between the regions with different environments while keeping the environmental conditions separate. There is a need to minimize the time that certain items spend in certain conditions. For example, there are strict regulations on food safety, which limit how long frozen items can spend at ambient temperatures. This issue can be addressed by ensuring fast and efficient transfer of items, while allowing a more comfortable and safer working environment for human workers and protecting machinery from detrimental environmental conditions. Summary A transfer mechanism is provided for transferring one or more items between a first region and a second region, wherein the first region is enclosed and maintained at a first environmental condition and the second region is at a second environmental condition, and the first and second regions are separated to restrict the passage of air between the first region and the second region, the transfer mechanism comprising: a fixed structure having at least one side wall, a first opening to the first enclosed region, and a second opening to the second enclosed region; a moveable structure mounted on a turntable arranged to rotate the moveable structure within the fixed structure, the moveable structure comprising one or more compartments; a ceiling above the moveable structure; wherein the turntable is configured to rotate the moveable structure to move a compartment of the one or more compartments between: i) a first open position in which the compartment is aligned with the first opening of the fixed structure to permit items to be transferred between the compartment and the first region; ii) a second open position in which the compartment is aligned with the second opening of the fixed structure to permit items to be transferred between the compartment and the second region; and iii) a closed position between the first open position and the second open position, in which access to the compartment is blocked by the at least one side wall of the fixed structure. The first and second environmental conditions may comprise temperature, atmosphere, and / or humidity. For example, the first environmental condition may comprise a frozen temperature, and the second environmental condition may comprise a chilled or ambient temperature. The first region may be maintained at the required temperature by a temperature control system (e.g. HVAC system). Cooling in the first region may be provided by chiller units. In other examples the first and second environmental conditions may comprise different atmospheres. For example, if a region is used for growing plants the atmosphere may be richer in carbon dioxide, or if a region is a laboratory for performing chemical reactions the atmosphere may be an inert atmosphere. Certain items may be required to be packaged in a sterile atmosphere. A region used for growing plants may also require a higher humidity and / or different intensity and wavelengths of light. The transfer mechanism facilitates the transfer of items between the first region and the second region, while keeping the air in the first region separated from the air in the second region. One application of the transfer mechanism is in fulfilment centres, where frozen goods are picked and packed to fulfil customer orders. In this example the first region is maintained at a frozen temperature and comprises a storage system for the frozen goods, and the second region is at a chilled or ambient temperature. Picking and packing of the goods takes place in the second (chilled or ambient) region, which has the advantage that human workers can work at a comfortable temperature without the need for personal protective equipment adapted for low temperatures. The second region being at a chilled temperature has the advantage of minimising the temperature differential between the first and second region, thus reducing thermal leakage and making it easier to keep the environmental conditions in the two regions separate, while still being an acceptable working environment. Also any machinery or equipment used for picking and packing can be maintained at ambient or chilled temperature, i.e. within its usual operating range. The transfer mechanism can also be used for replenishment, i.e. to restock the storage system with items. The one or more items can be individual products for customer orders ("eaches"), storage containers, storage frames, part completed orders, and / or completed orders. In the first open position the compartment is open to the first region, i.e. to an enclosed and controlled environment. The temperature and environment within the compartment will quickly equalise with that of the first region since air can pass freely into the compartment from the first region. In examples where the first region is at a frozen temperature, the compartment in the first open position is open to the frozen temperature so items in the compartment will also be at the frozen temperature. This is advantageous in situations where the items are frozen goods, because the goods are maintained at the appropriate temperature to maintain freshness and shelf life. In the second open position the compartment is open to the second region, e.g. to a chilled or ambient temperature. Items can be picked from the compartment at a chilled or ambient temperature. This arrangement of two distinct open positions means that a compartment in the moveable structure is never open at both the first and the second region at the same time. This helps to prevent the first and second environmental conditions from mixing, and in particular helps to maintain the first enclosed region at the first environmental condition. The fixed structure and the moveable structure together form an enclosure, which helps to maintain the environmental condition within the compartments of the moveable structure. The ceiling above the moveable structure may be supported by or mounted on the moveable structure, or supported by or mounted on the fixed structure. Alternatively, the ceiling above the moveable structure could be the ceiling of the building in which the transfer mechanism is located. The purpose of the ceiling is to separate the air inside the transfer mechanism from the air in the first and second regions. The moveable structure may comprise two or more compartments. Advantageously, multiple compartments increases the efficiency of the transfer mechanism; as items are being placed into or removed from a compartment in the first open position from the first region, items may be picked from a compartment in the second open position to the second region. The compartments may be separated by one or more dividers defining the compartments. The one or more dividers may substantially prevent the passage of air between the two or more compartments. The one or more dividers may be insulated in order to reduce heat transfer between compartments. The two or more compartments may comprise a first compartment and a second compartment, and the at least one side wall may comprise a pair of side walls, wherein the turntable is configured to rotate the moveable structure between: a first angular position in which the first compartment is in the first open position and the second compartment is in the second open position; and a second angular position in which both the first and second compartments are in the closed position. When the moveable structure is in the first angular position, the first compartment is in the first open position in which items can be transferred through the first opening between the first region and the first compartment, and the second compartment is in the second open position in which items can be transferred through the second opening between the second region and the second compartment. When the moveable structure is in the second angular position, both the first and second compartments are in the closed position in which the first opening and the second opening are each aligned with a respective one of the pair of side walls to block access to the first and second compartments respectively. When the moveable structure is in the second angular position the compartments and the side walls are aligned such that the passage of air into and out of the first and second compartments is restricted. The two or more compartments may comprise a first pair of compartments and a second pair of compartments, each compartment having a respective opening, and the at least one side wall comprises a pair of side walls, wherein the turntable is configured to rotate the moveable structure between: a first angular position in which the first pair of compartments are in the open position and the second pair of compartments are in the closed position; and a second angular position in which the first pair of compartments are in the closed position and the second pair of compartments are in the open position. When the moveable structure is in the first angular position, one of the first pair of compartments is in the first open position in which items can be transferred through the first opening between the compartment and the first region, the other of the first pair of compartments is in the second open position in which items can be transferred through the second opening between the compartment and the second region, and the second pair of compartments is in the closed position in which the second pair of compartments are aligned with the pair of side walls to block access to the second pair of compartments and restrict the passage of air into and out of the second pair of compartments. When the moveable structure is in the second angular position, the first pair of compartments are in the closed position, one of the second pair of compartments is in the first open position, and the other of the second pair of compartments is in the second open position. The ceiling may be supported by the at least one side wall of the fixed structure. Advantageously, the ceiling being supported by the fixed structure rather than the moveable structure reduces the weight of the moveable structure, and therefore the turntable requires less power to operate. The moveable structure and the fixed structure may be substantially cylindrical in shape. The side walls of the fixed structure may be shaped like an arc of a circle corresponding to the circular cross section of the moveable structure. The moveable structure is arranged to rotate inside the fixed structure in a similar manner to a revolving door. The moveable structure and the fixed structure may be arranged with a small gap between them and one or more seals and / or brushes are provided to restrict the flow of air through the gap. A gap is necessary for clearance to allow the moveable structure to rotate freely within the fixed structure, but keeping the gap small reduces the flow of air through the gap. Seals and / or brushes can further restrict airflow through the gap, thus helping to maintain the different environmental conditions in the first and second regions. The transfer mechanism may further comprise an air exchanger configured to exchange air inside a compartment of the one or more compartments of the rotatable enclosure with air at a different environmental condition outside the compartment. The air exchanger may exchange the air in the compartment with air in another compartment of the same transfer mechanism, or with air in a compartment of another transfer mechanism (for example, a second transfer mechanism may be adjacent or in close proximity to the transfer mechanism). In other examples, the air exchanger may exchange the air inside the compartment with air in the first region, or the second region. An advantage of the air exchanger is that the air in the compartment can be exchanged for air at a different environmental condition, e.g. a different temperature, so that when the compartment is moved into the open position the air inside the compartment is at the same environmental condition as the air in the first or second region. In cases where the first region is at a frozen temperature and the second region is at a chilled or ambient temperature, before a compartment is rotated into the first open position open to the colder air, the warmer air in the compartment is exchanged with colder air. This means that the compartment does not release warmer air into the colder first region. As a result, the energy required to maintain the first region at a colder temperature is not wasted. The air exchanger may comprise a first duct configured to remove the air inside the compartment, and a second duct configured to transfer the air at a different environmental condition into the compartment. The transfer of air into the compartment and out of the compartment may be done simultaneously. Fans may be used to direct the air along the first and second ducts. The air exchanger may be mounted in a fixed orientation relative to the fixed structure, and the first and second ducts may communicate with the moveable structure via one or more apertures in the ceiling. The purpose of mounting the air exchanger in a fixed orientation relative to the fixed structure is to enable air exchange while the air exchanger itself remains stationary. It would be impractical for the air exchanger to rotate with the moveable structure. The air exchanger may comprise a humidifier and / or a dehumidifier. The air exchanger may comprise sensors, for example temperature and humidity sensors. The air exchanger may comprise a control system that determines when to operate the air exchanger. For example, the control system may only operate the air exchanger when the compartment is in the closed position. The use of an air exchanger in examples where the moveable structure comprises four compartments is particularly advantageous. When the moveable structure is positioned so that two of the compartments are in the open position (one in the first open position and one in the second open position) and the other two compartments are in the closed position, the air exchanger can operate on the two compartments in the closed position at the same time as the compartment in the first open position can be loaded or unloaded with items, and the compartment in the second position is available for picking. This arrangement enables more efficient transfer of items, since the tasks of air exchange, picking, and loading / unloading can be carried out simultaneously. The moveable structure may comprise three compartments. An advantage of this arrangement is that a faster throughput of items can be achieved by the compartments being loaded and unloaded and picked simultaneously. This is particularly useful in examples where the items are arranged on storage frames. While items are being picked in the second region from a storage frame in a first compartment, a storage frame can be loaded into a second compartment from the first region ready for picking, and simultaneously an already-picked storage frame can be moved from a third compartment back into the first region. Each of the one or more compartments may comprise a compartment turntable configured to rotate within the compartment. The compartment turntable can change the orientation of a storage frame inside the compartment, for example to rotate the storage frame into a more convenient position for picking. The transfer mechanism may further comprise a dehumidifier for reducing humidity of air inside the moveable structure. A dehumidifier could be provided as part of the air exchanger described above, or separately. Dehumidification is particularly useful in examples where the first region is at a frozen temperature and the second region is at a chilled or ambient temperature. Given that warmer air can hold more moisture, there is a risk of condensation when items move from a warmer temperature to a colder temperature. Condensation can damage items or machinery, particularly if the first region is at a frozen temperature and the condensed moisture then freezes. The first opening and second opening of the fixed structure may each comprise a door. The door can be opened to permit items can be transferred through the first or second opening into or out of the one or more compartments of the moveable structure. The door can be closed to block access to the first or second opening. The provision of a door has the advantage that the door can be closed when the transfer mechanism is not in use, to provide further insulation. Also in examples where the transfer mechanism is provided with an air exchanger, the presence of a door permits the air exchanger to be used when the compartment is in the open position and the door closed. In the absence of a door, the air exchanger cannot be used when the compartment is in the open position (i.e. communicating with the first or second region), but only when the compartment is in the closed position. Each of the one or more compartments may be substantially airtight. Reducing or preventing the movement of air into and out of a compartment (except when the compartment is in the open position) helps to maintain the different environmental conditions in the two regions. The moveable structure may be insulated from the first and second regions. Insulation has the advantage of reducing thermal leakage between the first region and the second region through transfer mechanism. The compartments of the moveable structure may be insulated. Components of the moveable structure and / or the fixed structure and / or the ceiling may be insulated. A storage and retrieval system is provided, comprising: a first region comprising a storage system, wherein the first region is enclosed and maintained at a first environmental condition; a second region, wherein the second region is at a second environmental condition maintained at a second environmental condition; a wall separating the first region and the second region to substantially prevent the passage of air between the first region and the second region; at least one transfer mechanism as defined herein; and a work station located in the second region, located such that the second opening is accessible from the work station. The work station may be a pick station for picking items for customer orders, and / or a replenishment station for transferring items to the storage system. A separate pick station and replenishment station may be provided, or one work station can function both as a pick station and a replenishment station depending on requirements. The transfer mechanism permits items from the storage system in the first region to be picked at the pick station in the second region, and / or permits items from the second region to be transferred into the first region to restock the storage system, while maintaining separation of the first and second environmental conditions. The first and second environmental conditions may comprise temperature, atmosphere, and / or humidity. The first environmental condition may comprise a frozen temperature, and the second environmental condition may comprise a chilled or ambient temperature. The storage and retrieval system may further comprise one or more storage frames for moving items between the first region and the second region via the transfer mechanism. The one or more storage frames may contain one or more storage containers for holding items to be picked at the pick station. The one or more storage frames may comprise wheels such that the one or more storage frames can be rolled into and out of the moveable structure. This enables faster and more convenient throughput of storage frames and / or items on the storage frames. The one or more storage frames may comprise presentation positions for presenting the one or more storage containers such that items can be picked from the one or more storage containers in the presentation positions at the pick station. A storage container in a presentation position may be a convenient height, position, and angle for picking, therefore improving speed of picking and hence efficiency and throughput of the storage and retrieval system. The presentation positions ensure that picking is a more ergonomic process. Picking can be carried out by a human worker or a robot. In either case, the arrangement of items in presentation positions increase the efficiency of picking. The one or more storage frames may comprise one or more autonomous vehicles. For example, the one or more storage frames may comprise autonomous mobile robots (AMR). AM Rs can be used as an alternative to compartment turntables, or in addition. An advantage of using AM Rs instead of compartment turntables is reducing the complexity and number of moving parts in the transfer mechanism, and some storage and retrieval systems may already use AM Rs for other purposes An AM R carrying one or more items can pass through the transfer mechanism between the first region and the second region in order to move items between the storage system and the work station. The AMR can turn within the compartment in order to present the storage containers in the presentation positions to a worker at the work station. In examples where the AMR comprises a double-sided storage frame with presentation positions on both sides, once items have been picked from one side the AMR can rotate so that the presentation positions on the other side are accessible from the work station. Alternatively an AMR can be used to place a storage frame in a compartment in the appropriate orientation, or to retrieve a storage rack from a compartment, but the AMR remains within the same region. A method of transferring items between the first region and the second region is provided, using the transfer mechanism as defined herein, the method comprising steps of: i) when a compartment of the moveable structure is in the first open position, moving one or more items from the first region through the first opening into the compartment; ii) rotating the moveable structure until the compartment is in the second open position where the storage frame is accessible from the second region through the second opening; iii) transferring an item from the compartment to the second region through the second opening; OR wherein the method comprises the above steps carried out in reverse order to transfer items from the second region to the first region. The method steps can also be described as follows: i) when a compartment of the moveable structure is in the first or second open position, transferring one or more items into the compartment from the first or the second region respectively; ii) rotating the moveable structure to move the compartment from the first or second open position to the other of the first or second open position; and iii) transferring one or more items out of the compartment into the other of the first or the second region. The one or more items to be transferred may comprise a storage frame. Alternatively, the one or more items may comprise individual items for customer orders ("eaches"), partially or fully completed orders, storage containers, or pallets of items to be stored in the storage system. In examples where the work station is a pick station, the storage frame may be removed from the compartment and moved closer to the pick station for more convenient and faster picking, or the storage frame may remain inside the compartment while items are picked from the storage frame through the second opening. In examples where the work station is a replenishment station, the one or more items to be transferred may include pallets or containers of items to be restocked in the storage system. In examples where the transfer mechanism comprises two or more compartments, the method may further comprise the step of moving a second storage frame from the first region into a second compartment through the first opening. This step can be carried out whenever possible depending on arrangement of compartments. In arrangements where the first and second compartments can both be in the first open position at the same time, the second storage frame can be moved from the first region into the second compartment in parallel with step i). In arrangements where the first and second compartments are disposed on opposite sides of the moveable structure, the second storage frame can be loaded into the second compartment of the transfer mechanism at the same time as items are being picked from the first storage frame in the first compartment. In other arrangements, step ii) may comprise rotating the moveable structure to a position in between the first open position and the second open position, such that the second compartment is the first open position and the second storage frame can be loaded into the second compartment. In examples where each of the one or more compartments comprises a compartment turntable, the method may further comprise the step of: before step iii), rotating the compartment turntable to change the orientation of the storage frame to enable items in the storage frame to be picked at the work station. Advantageously, the compartment turntable can rotate the storage frame to a position more convenient for picking. In examples where the transfer mechanism comprises an air exchanger, step ii) may comprise exchanging the air inside a compartment of the moveable structure with air at a different environmental condition outside the compartment. Air can be exchanged when the compartment is in the closed position. In some examples, the air exchange may be carried out while the moveable structure is rotating. Brief description of figures The disclosure is described with reference to the following figures, which are non-limiting examples of how the transfer mechanism may be implemented. Figure 1 is a schematic illustration of a transfer mechanism with compartments in the first and second open positions. Figure 2 is a schematic illustration of the same transfer mechanism with compartments in the closed position. Figure 3 is a top view of the transfer mechanism with compartments in the first and second open positions. Figure 4(a to n) is a schematic illustration of the use of a transfer mechanism with: (a) a first compartment in the first open position and a second compartment in the second open position (b) a first storage frame in the first region, preparing to enter the first compartment (c) the first storage frame within the first compartment (d) the first storage frame rotated within the first compartment (e) the moveable structure rotated such that the first and second compartments are in the closed position (f) the moveable structure rotated further such that the first compartment is in the second open position accessible to the pick station in the second region, and the second compartment is in the first open position with a second storage frame preparing to enter the second compartment from the first region (g) the second storage frame within the second compartment (h) the second storage frame rotated within the second compartment (i) the moveable structure rotated such that the first and second compartments are in the closed position (j) the moveable structure rotated further such that the first compartment is in the first open position and the second compartment is in the secondopen position accessible to the pick station in the second region (k) the first storage frame rotated in the first compartment preparing to exit into the first region, with a third storage frame preparing to enter the first compartment from the first region (I) the first storage frame having exited the first compartment (m) the third storage frame within the first compartment (n) the third storage frame rotated within the first compartment. Figure 5(a to c) is a top view of a transfer mechanism with (a) two compartments (b) three compartments (c) four compartments. Figure 6 is a schematic illustration of a transfer mechanism with an air exchanger. Figure 7 is a schematic illustration of a transfer mechanism with an air exchanger. Figure 8 is a schematic illustration of a transfer mechanism with air exchanger, showing air exchange between two compartments. Figure 9(a and b) shows two alternative arrangements of an air exchanger, (a) showing air exchange between two transfer mechanisms, and (b) showing air exchange between a compartment of a transfer mechanism and the first or second region. Figure 10 is a schematic illustration of a wall separating the first and second regions, with several transfer mechanisms arranged along the wall. Detailed description Figure 1 is a schematic illustration of a transfer mechanism 1. The transfer mechanism 1 is positioned between a first region 3a and a second region 3b. A wall 2 separates the first region 3a from the second region 3b. The position of the wall 2 is illustrated by a dashed line. The ceiling of the transfer mechanism is not shown for ease of illustration and understanding. The transfer mechanism 1 comprises a fixed structure 5 and a moveable structure 11. Both are substantially cylindrical in shape, and the moveable structure 11 is positioned inside the fixed structure 5. The moveable structure 11 is mounted on a turntable 13, which permits the moveable structure 11 to rotate within the fixed structure 5. The fixed structure 5 comprises side walls 7. In the illustrated example, the side walls comprise two side walls 7, namely a first side wall 7a and a second side wall 7b. The side walls 7a, 7b have a cross section shaped like an arc of a circle, in order to co-operate with the cylindrical shape of the moveable structure 11. The fixed structure comprises two openings 9, namely a first opening 9a and a second opening 9b. The first opening 9a is on the side of the transfer mechanism in the first region 3a, and the second opening 9b is on the side of the transfer mechanism in the second region 9b. The openings 9a, 9b are positioned between the first and second side walls 7a, 7b of the fixed structure 5. In this example the moveable structure 11 comprises two compartments 15, namely a first compartment 15a and a second compartment 15b. In the illustrated example the two compartments 15 are cut-outs from the cylindrical block of the moveable structure 11. In other examples, the moveable structure may have only a single compartment, or more than two compartments, for example three or four compartments. Any suitable number, shape, and arrangement of compartments can be used. The transfer mechanism 1 can be used to transfer items between the first region 3a and the second region 3b. The items could be products for customer orders, storage containers, storage frames, part completed orders, and / or completed orders. The figure illustrates a storage frame 25 inside each of the two compartments 15, and two further storage frames 25 in the first region 3a. The storage frames contain storage containers 27. A pick station 23 is located within the second region 3b. The storage frame 25 within the compartment 15b in the second open position is accessible from the pick station 23. In the illustrated example the storage frames comprise presentation positions in which the storage containers are presented at the pick station 23. The presentation positions are at an appropriate height and angle for ergonomic picking by a worker at the pick station 23. The compartments 15 are each provided with a compartment turntable 17 located inside the compartment, for changing the orientation of a storage frame 25 inside the compartment. In other examples, storage frames 25 can be manipulated by autonomous mobile robots (AMRs), and / or the storage frames themselves can be autonomous vehicles. In the illustrated example, a storage frame 25 is located at an input position 19 within the first region 3a close to the first opening 9a of the transfer mechanism. Another storage frame 25 is located at an output position 21. The input position 19 and the output position 21 are each provided with a turntable for orienting the storage frame 25 for entry into or exit from the transfer mechanism. An advantage of providing separate input and output positions 19, 21 is that as soon as a storage frame 25 has exited the compartment to the output position 21, another storage frame in the input position 19 can be ready to enter the compartment 15a. This improves the throughput of storage frames 25 between the first and second regions 3a, 3b, and therefore improves the efficiency and speed of picking. In use, as the moveable structure 11 rotates within the fixed structure 5, the compartments 15 change their position. In Figure 1, the first compartment 15a is in a first open position, i.e. the first compartment 15a is aligned with the first opening 9a and open to the first region 3a. In the first open position, items can be transferred between the first region 3a and the compartment through the first opening 9a. The second compartment 15b is in a second open position, i.e. the second compartment 15b is aligned with the second opening 9b and open to the second region 3b. In the second open position, items can be transferred between the second region 3b and the compartment through the second opening 9b. The transfer mechanism works in a similar way to a revolving door; items enter through one opening, the moveable structure rotates, and the items can exit through the other opening. This arrangement permits fast and convenient transfer of items through the transfer mechanism, while keeping the environmental conditions of the two regions separate. Figure 2 schematically illustrates the transfer mechanism 1 in a different position. The moveable structure 11 has rotated clockwise by around 90° from the position as illustrated in Figure 1. The first compartment 15a is now in a closed position i.e. the first compartment 15a is aligned with the first side wall 7a. The first side wall 7a is blocking the exit of the first compartment 15a. Similarly the second compartment 15b is in a closed position, i.e. aligned with the second side wall 7b such that the second side wall 7b is blocking the exit of the second compartment 15b. In this position, no items can enter or exist the compartments 15 (again, the ceiling is not shown for ease of illustration). Once the moveable structure 11 has rotated clockwise by a further 90°, the moveable structure will be in the opposite orientation to that illustrated in Figure 1, i.e. the first compartment 15a will be in the second open position, open to the second region 3b through the second opening 9b, and the second compartment 15b will be in the first open position, open to the first region 3a through the first opening 9a. Figure 3 is a top view of the transfer mechanism 1 with compartments in the first and second open positions. The compartment turntables 17a and 17b of the first and second compartments 15, 15b respectively can more easily be seen. The pick station 23 is located close to the second opening 9b of the fixed structure, so items can be picked directly from a storage frame in a compartment 15b in the second open position. In other examples, the storage frame may be moved from the compartment into the second region 3b for ease of picking. Figure 4 is a series of top views of a transfer mechanism, showing the transfer mechanism in various positions to illustrate its operation. Again, the ceiling is not shown for ease of visualisation. In Figure 4(a), the first compartment 15a is in the first open position open to the first region 3a, and the second compartment 15b is in the second open position open to the second region 3b. In Figure 4(b), a first storage frame 25a in the first region 3a is at the input position 19, preparing to enter the first compartment 15a. The arrow indicates the direction of movement. In Figure 4(c) the first storage frame 25a has entered the first compartment 15a through the first opening 9a. In Figure 4(d) the compartment turntable 17a in the first compartment 15a has rotated anticlockwise by around 45° from the position in Figure 4(c), to align the first storage frame 25a within the first compartment 15a. The arrow indicates the direction of rotation of the compartment turntable 17a. In Figure 4(e) the moveable structure 11 has rotated around 90° anticlockwise. The first and second compartments 15a, 15b are now in the closed position. The arrow indicates the direction of rotation of the moveable structure 11. The compartments 15a, 15b are aligned with the side walls 7 such that access to the inside of the compartments is blocked. In Figure 4(f) the moveable structure rotated a further 90°. The first and second compartments 15a, 15b have exchanged places from the position illustrated in Figure 4(a). The first compartment 15a is in the second open position accessible to the pick station 23 in the second region 3b, and the second compartment 15b is in the first open position accessible from the first region 3a. A second storage frame 25b is in the input position 19 in the first region 3a, preparing to enter the second compartment 15b. In Figure 4(g), the second storage frame 25b has entered the second compartment 15b through the first opening 9a. In Figure 4(h), the second storage frame 25b has been rotated within the second compartment 15b by the compartment turntable 15b. In all of Figures 4(f), 4(g), and 4(h), items can be picked from the first storage frame 25a through the second opening 9b. In the illustrated arrangement the items can be picked directly from the first storage frame 25a while the first storage frame 25a remains inside the first compartment 15a. In Figure 4(i), the moveable structure 11 has rotated a further 90° anticlockwise. The first and second compartments 15a, 15b are now in the closed position again. In Figure 4(j), the moveable structure 11 has rotated a further 90° anticlockwise, and is now back in the starting position as illustrated in Figure 4(a), having completed one full turn. The first compartment 25a is in the first open position and the second compartment 15b is in the second open position. The second storage frame 25b is now accessible to the pick station 23 in the second region 3b. In Figure 4(k), the first storage frame 25a has been rotated by the compartment turntable 17a in the first compartment 15a preparing to exit into the first region 3a. A third storage frame 25c is in the input position 19, preparing to enter the first compartment 15a from the first region 3a. In Figure 4(1), the first storage frame 25a has exited the first compartment 15a through the first opening 9a. The first storage frame 25a is now in the output position 21 in the first region 3a, preparing to move away from the transfer mechanism 1 and back to the storage system. In Figure 4(m), the third storage frame 25c has entered the first compartment 15a through the first opening 9a. In Figure 4(n), the third storage frame 25c has been rotated by the compartment turntable 17a within the first compartment 15a. The sequence of movements continues in a similar manner, in order to present a series of different storage frames 25 at the pick station 23. Once a storage frame 25 has been picked, it is returned through the transfer mechanism 1 back to the first region 3a, from which it can be taken back into the storage structure. The storage frame is replaced by the next storage frame in the sequence. Although Figures 1-4 have been described above with reference to picking, the transfer mechanism can equally be used for replenishment of stock in a storage system in the first region. A replenishment station may be provided instead of or as well as the pick station 23 illustrated. Figures 1-4 illustrate a transfer mechanism with two compartments. In other examples, different numbers of compartments can be provided. Figure 5(a to c) is a top view of a transfer mechanism with (a) two compartments (b) three compartments (c) four compartments, showing the input and output positions of in the first region. Figure 5(a) shows a transfer mechanism with two compartments, as described above. The compartments 15a and 15b are arranged on opposite sides of the moveable structure 11, so that when the first compartment 15a is in the first open position, the second compartment 15b is in the second open position, and vice versa. An input position 19 and an output position 21 are located close to the first opening 9a in the first region 3a. Advantageously, separate input and output positions allow the next storage frame to enter the compartment as soon as the compartment has been vacated by the previous storage frame. Figure 5(b) shows a transfer mechanism with three compartments. In this arrangement, two compartments 15a, 15c are in the first open position at the same time, while another compartment 15b is in the second open position. The first opening may be wide enough to provide access to two compartments, or alternatively two first openings can be provided, one for each of the two compartments in the first open position. The input position 19 is adjacent to one compartment in the first open position, and the output position 21 is adjacent to the other compartment in the first open position. Advantageously, in this arrangement a storage frame can be loaded into the compartment 15a from the input positon 19, and in parallel a storage frame can be unloaded from the compartment 15c to the output position 21. This makes the transfer of items through the transfer mechanism faster and more efficient. The moveable structure 11 then rotates by around 120° anticlockwise, so the full compartment 15a moves to the second open position to be picked from, and the empty compartment 15c moves to a position adjacent to the input position 19 for another storage frame to be loaded into the compartment. Figure 5(c) shows a transfer mechanism with four compartments. In this arrangement, three compartments 15a, 15c, 15d are in the first open position at the same time, while another compartment 15b is in the second open position. The first opening may be wide enough to provide access to three compartments, or alternatively three first openings can be provided, one for each of the three compartments in the first open position. As well as the input position 19 and output position 21, an input / output position 20 is provided. This improves the flexibility of the system, since the input / output position can be used either to input a storage frame into the compartment or to output a storage frame from the compartment, depending on the specific requirements at that time. As an alternative arrangement, a transfer mechanism with four compartments may be arranged such that when a first compartment is in the first open position, a second compartment is in the second open position, and the third and fourth compartments are in the closed position. In this arrangement the moveable structure would be the same as illustrated in Figure 5(c), but positioned centrally between the first region 3a and the second region 3b, and with the fixed structure 11 having a first opening arranged for one compartment. The above arrangements are non-limiting examples only; any suitable number or arrangement of compartments can be used. Figures 6 and 7 are schematic illustrations of a transfer mechanism 1 with an air exchanger 29. The air exchanger 29 is configured to exchange the air within a compartment with air outside the compartment at a different environmental condition, for example a different temperature and / or humidity. In Figure 6 the two compartments 15a and 15b are in the closed position, and in Figure 7 the first compartment (not shown) is in the first open position and the second compartment 15b is in the second open position. The transfer mechanism 1 comprises a ceiling 39, which is supported by and mounted on the side walls 7 of the fixed structure 5. The ceiling is shown in Figure 7, but not shown in Figure 6 for ease of visualisation. Other features of the transfer mechanism 1 areas described above with reference to Figures 1 and 2, so will not be described in detail here. The air exchanger 29 in this example is configured to exchange air between two compartments 15a and 15b when in the closed position. The air exchanger 29 comprises a first connector 33a and second connector 33b that connect to apertures in the ceiling 39, and ducting 31 extending between the first connector 33a and the second connector 33b. When the two compartments 15a, 15b are in the closed position, the air exchanger 29 communicates with the compartments. Air can flow between the compartments, through the apertures to the connectors 33a, 33b and into the air exchanger. Figure 8 is a schematic illustration of a transfer mechanism 1 with air exchanger 29, showing air exchange between two compartments 15a, 15b. The ducting 31 comprises a first duct 31a and a second duct 31b. Two connectors 33a, 33b are provided, with a first connector 33a connecting the ducts 31a, 31b to the first compartment 15a, and a second connector 33b connecting the ducts 31a, 31b to the second compartment 15b. The connectors are mounted on the ceiling 39, which is supported by the side walls 7 of the fixed structure 11. The connectors 33a, 33b comprise a first aperture 35a and second aperture 35b respectively in the ceiling 39. The apertures 35a, 35b are positioned such that the connectors 33a, 33b communicate with the compartments 15a, 15b respectively when in the closed position. Fans 37 are provided to direct the flow of air through the first and second ducts 31a 31b. The direction of airflow is indicated by the arrows on Figure 8. In use, when the moveable structure 11 is rotated such that the compartments 15a, 15b are in the closed position, the fans 37 are activated in order to push air along the first and second ducts 31a, 31b. The first duct 31a carries air from the first compartment 15a to the second compartment 15b, and in parallel the second duct 31b carries air in the opposite direction, from the second compartment 15b to the first compartment 15a. This permits the air in the two compartments 15a, 15b to be exchanged. For example, Figure 4 (d) illustrates a transfer mechanism with the first compartment 15a in the first open position and the second compartment 15b in the second open position. If the first region 3a is at a frozen temperature and the second region 3b is at a chilled or ambient temperature, the air inside the first compartment 15a will be at a frozen temperature and the air inside the second compartment 15b will be at a chilled or ambient temperature. When the turntable rotates the moveable structure 11 so that the compartments 15a, 15b are in the closed position as in Figure 4(e), the air exchanger can be operated to swap the air in the compartments so that the first compartment 15a is at a chilled or ambient temperature and the air inside the second compartment 15b is at a frozen temperature. When the turntable rotates further so that the first compartment 15a in the second open position and the second compartment 15b is in the first open position as in Figure 4(e), the chilled or ambient temperature of the air inside the first compartment 15a will be substantially the same chilled or ambient temperature as the air in the second region 3b on the other side of the second opening 9b. Similarly, the frozen temperature of the air inside the second compartment 15b will be substantially the same frozen temperature as the air in the first region 3a on the other side of the first opening 9a. This means that heat is not lost through the openings 9a, 9b as the moveable structure rotates to transfer items into and out of the transfer mechanism. Figure 9(a and b) shows two alternative arrangements of an air exchanger. Figure 9(a) illustrates two adjacent transfer mechanisms la and lb, each with a single compartment 15. The transfer mechanisms la, lb share an air exchanger 29. Instead of exchanging air between different compartments of the same transfer mechanism, in the illustrated arrangement air is exchanged between different transfer mechanisms la, lb. Again, the ducting 31 comprises a first duct 31a and a second duct 31b. Each transfer mechanism la, lb is provided with a respective connector 33a, 33b. The first connector 33a connects the ducts 31a, 31b to the compartment 15 of the first transfer mechanism la, and a second connector 33b connects the ducts 31a, 31b to the compartment 15 of the second transfer mechanism lb. The connectors 33a, 33b are each mounted on the ceiling 39 of the respective transfer mechanisms la, lb. The first connector 33a has a first aperture 35a in the ceiling 39 of the first transfer mechanism la, and the second connector 33b has a second aperture 35b in the ceiling 39 of the second transfer mechanism lb. The apertures 35a, 35b are positioned such that the connectors 33a, 33b communicate with the compartments 15 of the respective transfer mechanisms. Although in the example illustrated here the transfer mechanisms la, lb have only a single compartment 15, in other examples the air exchanger can exchange air between transfer mechanisms having a different number of compartments. Figure 9(b) illustrates air exchange between a compartment 15 of a transfer mechanism 1 and the first or second region 3a, 3b. In this example the air is exchanged with the first or second region directly rather than with another compartment. Again, this arrangement saves energy by ensuring that the air inside the compartment 15 is at the same temperature as the air on the other side of the opening 9a, 9b before being moved into the first / second open position. The transfer mechanism 1 is provided with a connector 33 mounted on the ceiling 39, with an aperture 35 in the ceiling to allow air to pass between the connector 33 and the compartment 15. The connector 33 connects the ducts 31a, 31b to the compartment 15 of the transfer mechanism 1. The first duct 31a transfers air between the connector 33 and the first region 3a, and the second duct 31b transfers air between the connector 33 and the second region 3b. In use, the compartment 15 in the first open position receives items to be transferred. In the first open position, the compartment 15 will fill with air from the first region 3a (which may be at a frozen temperature). The turntable rotates the moveable structure 11 until the compartment 15 is in the closed position. While in the closed position, the air inside the compartment 15 is returned to the first region, through the aperture 35 into the connector 33 and along the first duct 31a, directed by the fan 37. In parallel, air from the second region (which may be at a chilled or ambient temperature) passes through the second duct 31b into the connector 33 and through the aperture 35 into the compartment 15. The compartment 15 is now filled with air from the second region. The turntable rotates the moveable structure into the second open position. Since the air in the compartment has been exchanged, the air inside the compartment is at the same temperature (or other environmental condition) as the air in the second region 3b on the other side of the first opening 3b. The same steps can be carried out in reverse to transfer items from the second region 3b to the first region 3a. In this way, no energy is lost through air passing between the first region 3a and the second region 3b. Although this example is illustrated using a transfer mechanism 1 with a single compartment 15, in other examples the air exchanger can exchange air between one of several compartments in a transfer mechanism and the first / second regions. Figure 10 is a schematic illustration of a wall 2 (indicated by a dashed line) separating the first and second regions 3a, 3b, with several transfer mechanisms 1 arranged along the wall 2. The transfer mechanisms 1 can be used for picking customer orders, or for replenishing the storage system, or a combination of both. In some examples, transfer mechanisms 1 can be used flexibly, i.e. used either 5 to transfer items to be picked for customer orders or to transfer items to restock the storage system, depending on the requirements at any particular time. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and / or shown in 10 the drawings, whether or not particular emphasis has been placed thereon. 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.

Claims

1. A transfer mechanism for transferring one or more items between a first region and a second region, wherein the first region is enclosed and maintained at a first environmental condition and the second region is at a second environmental condition, and the first and second regions are separated to restrict the passage of air between the first region and the second region, the transfer mechanism comprising:a fixed structure having at least one side wall, a first opening to the first enclosed region, and a second opening to the second enclosed region;a moveable structure mounted on a turntable arranged to rotate the moveable structure within the fixed structure, the moveable structure comprising one or more compartments;a ceiling above the moveable structure;wherein the turntable is configured to rotate the moveable structure to move a compartment of the one or more compartments between:i) a first open position in which the compartment is aligned with the first opening of the fixed structure to permit items to be transferred between the compartment and the first region;ii) a second open position in which the compartment is aligned with the second opening of the fixed structure to permit items to be transferred between the compartment and the second region; andiii) a closed position between the first open position and second open position, in which access to the compartment is blocked by the at least one side wall of the fixed structure.

2. The transfer mechanism of any one of the preceding claims, wherein the moveable structure comprises two or more compartments.

3. The transfer mechanism of claim 2, wherein the two or more compartments comprise a first compartment and a second compartment, and the at least one side wall comprises a pair of side walls, wherein the turntable is configured to rotate the moveable structure between:a first angular position in which the first compartment is in the first open position and the second compartment is in the second open position; anda second angular position in which both the first and second compartments are in the closed position.

4. The transfer mechanism of claim 2, wherein the two or more compartments comprise a first pair of compartments and a second pair of compartments, each compartment having a respective opening, and the at least one side wall comprises a pair of side walls, wherein the turntable is configured to rotate the moveable structure between:a first angular position in which the first pair of compartments are in the first and second open position and the second pair of compartments are in the closed position; anda second angular position in which the first pair of compartments are in the closed position and the second pair of compartments are in the first and second open position.

5. The transfer mechanism of any preceding claim, wherein the ceiling is supported by the at least one side wall of the fixed structure.

6. The transfer mechanism of any one of the preceding claims, wherein the moveable structure and the fixed structure are substantially cylindrical in shape.

7. The transfer mechanism of claim 6, wherein the moveable structure and the fixed structure are arranged with a small gap between them and one or more seals and / or brushes are provided to restrict the flow of air through the gap.

8. The transfer mechanism of any one of the preceding claims, further comprising an air exchanger configured to exchange air inside a compartment of the one or more compartments of the moveable structure with air at a different environmental condition outside the compartment.

9. The transfer mechanism of claim 8, wherein the air exchanger comprises a first duct configured to remove the air inside the compartment, and a second duct configured to transfer the air at a different environmental condition into the compartment.

10. The transfer mechanism of claim 8 or claim 9, wherein the air exchanger is mounted in a fixed orientation relative to the fixed structure, and the air exchanger exchanges air with the moveable structure via one or more apertures in the ceiling.

11. The transfer mechanism of any one of the preceding claims, wherein each of the one or more compartments comprises a compartment turntable configured to rotate within the compartment.

12. The transfer mechanism of any one of the preceding claims, wherein the first opening of the fixed structure comprises a door and / or second opening of the fixed structure comprises a door.

13. A storage and retrieval system, comprising:a first region comprising a storage system, wherein the first region is enclosed and maintained at a first environmental condition;a second region, wherein the second region is at a second environmental condition maintained at a second environmental condition;a wall separating the first region and the second region to restrict the passage of air between the first region and the second region;at least one transfer mechanism as defined in any one of the preceding claims; anda work station located in the second region, located such that the second opening is accessible from the work station.

14. The storage and retrieval system of claim 13, wherein the work station is a pick station for picking items for customer orders, and / or a replenishment station for transferring items to the storage system.

15. The storage and retrieval system of claim 13 or claim 14, wherein the first and second environmental conditions comprise temperature, atmosphere, and / or humidity, optionally wherein the first environmental condition comprises a frozen temperature and the second environmental condition comprises a chilled or ambient temperature.

16. The storage and retrieval system of any one of claims 12 to 15, further comprising one or more storage frames for moving items between the first region and the second region via the transfer mechanism, optionally wherein the one or more storage frames comprise wheels such that the one or more storage frames can be rolled into and out of the moveable structure.

17. The storage and retrieval system of claim 16, wherein the one or more storage frames comprise presentation positions for presenting one or more storage containers such that items can be picked from the one or more storage containers in the presentation positions at the work station.

18. The storage and retrieval system of claim 16 or claim 17, wherein the one or more storage frames comprises one or more autonomous vehicles.

19. A method of transferring items between the first region and the second region, using the transfer mechanism as defined in any one of claims 1 to 12, the method comprising steps of:i) when a compartment of the moveable structure is in the first open position, moving one or more items from the first region through the first opening into the compartment;ii) rotating the moveable structure until the compartment is in the second open position where the storage frame is accessible from the second region through the second opening;iii) transferring an item from the compartment to the second region through the second opening;ORwherein the method comprises the above steps carried out in reverse order to transfer items from the second region to the first region.

20. The method of claim 19, wherein the one or more items to be transferred comprises a storage 5 frame.

21. The method of claim 20, wherein the transfer mechanism comprises two or more compartments, the method further comprising a step of moving a second storage frame from the first region into a second compartment through the first opening..

022. The method of claim 20 or 21, wherein each of the one or more compartments comprises a compartment turntable, the method further comprising the step of:before step iii), rotating the compartment turntable to change the orientation of the storage frame to enable items in the storage frame to be picked at the work station..

523. The method of any one of claims 19 to 22, wherein the transfer mechanism comprises an air exchanger, and step ii) comprises exchanging the air inside a compartment of the moveable structure with air at a different environmental condition outside the compartment.21

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