A system, an aisle cart and a rack

Abstract

A system (1) for storing an item (2), the system (1) comprising a rack (10), an aisle cart (40) and a row cart (60), the rack (10) comprising: an aisle (20); an aisle rail (22), being a rail extending along the aisle (20); and a plurality of rows (30), each row (30) having a respective entrance at the aisle (20); the aisle cart (40) being a cart configured to travel on the aisle rail (22) and to transport the row cart (60) and the item (2) to the entrance of a designated row (30); the row cart (60) being a cart configured to transport the item (2) from the aisle cart (40), along the designated row (30), to a storage position (16) in the designated row (30); wherein the aisle rail (22) comprises a hollow beam (50); wherein the aisle cart (40) comprises a support wheel (46), being a wheel arranged to roll on a top surface (54t) of the hollow beam (50) of the aisle rail (22) and to support the aisle cart (40) when the aisle cart (40) travels on the aisle rail (22); and a guide member (110), being a member configured to guide the aisle cart (40) along the hollow beam (50) of the aisle rail (22) by engaging the rack (10).

Description

[0001] A SYSTEM, AN AISLE CART AND A RACK

[0002] TECHNICAL FIELD

[0003] The present inventive concept relates, in general, to storage of items in a rack.

[0004] BACKGROUND

[0005] Automated storage systems are often used in warehouses and distribution facilities. Such a system may comprise a rack, wherein automated vehicles transport items to and from their storage positions in the rack. The rack often comprises several stories, wherein each story comprises aisles and rows. For each aisle there are generally a plurality of rows extending from the aisle, wherein the items are stored in the rows.

[0006] There are many types of automated vehicles that can be used to transport items within the rack. In some cases aisle carts and row carts are used. The aisle cart transports the row cart and the item to the entrance of a row. The row cart then leaves the aisle cart and carries the item into the row and places the item at the storage position in the row.

[0007] SUMMARY

[0008] It is an objective of the present inventive concept to facilitate low maintenance of an automated storage system. It is a further objective to facilitate smooth transport in the automated storage system. It is a further objective to facilitate fast transport in the automated storage system.

[0009] These and other objectives of the inventive concept are at least partly met by the invention as defined in the independent claims. Preferred embodiments are set out in the dependent claims.

[0010] According to a first aspect there is provided a system for storing an item, the system comprising a rack, an aisle cart and a row cart, the rack comprising: an aisle; an aisle rail, being a rail extending along the aisle; and a plurality of rows, each row having a respective entrance at the aisle; the aisle cart being a cart configured to travel on the aisle rail and to transport the row cart and the item to the entrance of a designated row; the row cart being a cart configured to transport the item from the aisle cart, along the designated row, to a storage position in the designated row; wherein the aisle rail comprises a hollow beam; wherein the aisle cart comprises a support wheel, being a wheel arranged to roll on a top surface of the hollow beam of the aisle rail and to support the aisle cart when the aisle cart travels on the aisle rail; and a guide member, being a member configured to guide the aisle cart along the hollow beam of the aisle rail by engaging the rack.

[0011] The item may be a pallet, with or without goods. Alternatively, the item may be any form of goods, crate or box.

[0012] The aisle may extend in a first direction. Each row may extend in a second direction from its respective entrance at the aisle. The first direction, in which the aisle extends, may be perpendicular to the second direction, in which the rows extend. There may be rows extending from the aisle both on the left and right side of the aisle.

[0013] The designated row may be any one of the plurality of rows in which the item is intended to be stored.

[0014] The rack may further comprise at least one loading position where the aisle cart may collect the item. The aisle cart may approach the loading position and collect the item by pulling the item onto the aisle cart, e.g. by using a belt conveyor of the aisle cart. The loading position may be a position at the edge of the rack. The loading position may be an elevator configured to transport the item to a designated story of the rack. The loading position may be a buffer conveyor, e.g. a buffer conveyor at a designated story of the rack, where items are waiting for further transport to their respective designated storage position. Thus, the system may be configured to move the item from the loading position, via the aisle and the designated row, to the storage position, or vice versa.

[0015] The aisle may comprise a pair of aisle rails. Similarly, each row may comprise a row rail, being a rail extending along the row. Each row may comprise a pair of row rails. The aisle cart may comprise a set of support wheels, e.g. four support wheels, e.g. a left pair of support wheels and a right pair of support wheels. One or more of the support wheels may be driven by a motor, e.g. a motor comprised in the aisle cart to propel the aisle cart along the aisle rail.

[0016] The row cart may comprise a wheel, e.g. a set of wheels, e.g. four wheels, e.g. a left pair of wheels and a right pair of wheels. One or more of the wheels of the row cart may be driven by a motor, e.g. a motor comprised in the row cart to propel the aisle cart along the row rail.

[0017] The aisle cart may comprise a platform, being configured to support the support wheel of the row cart while the aisle cart transports the row cart. When the aisle cart transports the row cart and the item along the aisle, the row cart may stand on the platform of the aisle cart. When the aisle cart transports the row cart and the item along the aisle, the item may stand on the belt conveyor.

[0018] The row cart may comprise a lifting device. Before the row cart transfers the item into the designated row, the row cart may lift the item using the lifting device. Thus, the item may be lifted up from the belt conveyor of the aisle cart. The lifting device may be configured to lift the item by lowering the support wheels of the row cart, e.g. lowering the support wheels of the row cart relative to the chassis of the row cart. In other words, a separation between the support wheels of the row cart and the chassis of the row cart may be increased to lift the item.

[0019] The row cart may place the item at the storage position in the designated row by lowering the item using the lifting device. The lifting device may be configured to lower the item by raising the wheels of the row cart, e.g. raising the wheels of the row cart relative to the chassis of the row cart. In other words, a separation between the support wheels of the row cart and the chassis of the row cart may be reduced to lower the item.

[0020] It is a realization that an aisle rail comprising a hollow beam is advantageous. The hollow beam may have a high resistance to several types of ferees as illustrated by the examples below. As a first example, the hollow beam may have a high resistance to bending forces in multiple directions. For example, a hollow beam mounted horizontally may have a high resistance to bending both around the horizontal and vertical axis. In contrast, an I-beam with an upper and a lower flange may, when mounted horizontally, may have a high resistance to bending around the vertical axis but a low resistance to bending around the horizontal axis. As a second example, the hollow beam may have a high resistance to shear forces in multiple directions. As a third example, the hollow beam may have a high resistance to torsion.

[0021] The hollow beam may be a hollow structural section (HSS) metal profile. A HSS beam with a square cross-section is sometimes referred to as a square hollow section (SHS). A HSS beam with a square cross-section is sometimes referred to as a rectangular hollow section (RHS).

[0022] The hollow beam of the aisle rail may have a square or rectangular cross-section. Thus, the hollow beam may be a SHS metal profile or a RHS metal profile.

[0023] The hollow beam may be made of steel.

[0024] It is a realization that the system is a low maintenance system. This may be, at least partly, due to the above mentioned high resistance to several types of ferees. The aisle rail may be straight and / or smooth due to the above mentioned high resistance to several types of ferees. For example, when an aisle rail comprises two or more hollow beams, the top surfaces of the hollow beams may align well such that smooth joints are provided. Smooth joints may result in less wear on the support wheels of the aisle cart. Time and / or money spent on maintenance may thus be low.

[0025] Further, as the aisle rail may be straight and / or smooth, the aisle cart may travel faster. There may also be little vibrations and / or bumps affecting sensitive items. Thus, storage of sensitive items is facilitated.

[0026] It is a realization that the guide member may prevent derailing of the aisle cart. Thus, the guide member may be configured to prevent derailing of the aisle cart. Prevention of derailing may be particularly important when using an aisle rail comprising a hollow beam as a hollow beam may lack flanges to steer a support wheel. Thus, the hollow beam and the guide member may cooperate to provide an advantageous system.

[0027] The guide member may be a member configured to prevent movements of the aisle cart that deviates more than a threshold distance from the aisle rail.

[0028] The guide member may be a member configured to prevent movements of the aisle cart that deviates more than a threshold distance in the horizontal direction from the aisle rail. The threshold distance in the horizontal direction may be equal to a factor times the width of the hollow beam. The factor may be 0.01 , 0.1 , 0.5, 0.7 or 0.9.

[0029] The guide member may be a member configured to prevent movements of the aisle cart that deviates more than a threshold distance in the vertical direction from the aisle rail. The threshold distance in the vertical direction may be at least 1 mm. The threshold distance in the vertical direction may be less than 15 mm. In particular, threshold distance in the vertical direction may be 5 mm.

[0030] The guide member may be configured to engage the hollow beam of the aisle rail of the rack; and / or engage a portion of the rack that extends in parallel with the hollow beam of the aisle rail of the rack.

[0031] The guide member may e.g. be configured to engage a side surface of the hollow beam and / or engage a bottom surface of the hollow beam and / or engage a ledge extending in parallel with the hollow beam of the aisle rail.

[0032] The guide member may be part of one of the support wheels of the aisle cart. For example, the guide member may comprise one or more flange of the support wheel. Said flange being configured to extend along a side surface of the hollow beam and engage said side surface if the aisle cart starts to deviate from the aisle rail.

[0033] Alternatively, and advantageously, the guide member may be a member separate from the support wheel. Such a member separate from the support wheel may provide smooth guiding and / or guiding with little friction.

[0034] The guide member of the aisle cart may comprise a first guide wheel, being a wheel arranged to roll on a first side surface of the hollow beam. The first side surface of the hollow beam may be a surface of the hollow beam perpendicular to the top surface of the hollow beam. The first guide wheel may be configured to rotate around a vertical axis.

[0035] The guide member of the aisle cart may further comprise a second guide wheel, being a wheel arranged to roll on second side surface of the hollow beam, the second side surface of the hollow beam being opposite to the first side surface of the hollow beam. The second side surface of the hollow beam may be a surface of the hollow beam perpendicular to the top surface of the hollow beam. The second guide wheel may be configured to rotate around a vertical axis.

[0036] One or more guide wheels may provide smooth guiding of the aisle cart. Thus, the aisle cart may travel faster. Further, the aisle cart may follow the aisle rail with a low amount of vibrations and / or bumps. Thus, storage of sensitive items is facilitated. Further, the aisle cart may follow the aisle rail with little friction. Thus, energy efficient transport is facilitated. A guide wheel (first or second) may be arranged such that a horizontal distance between the center of the support wheel and said guide wheel is at least half the hollow beam width (HBW). For example, said horizontal distance may be 0.51 *HBW, such that the aisle cart moving with the support wheel centered at the hollow beam top surface is prevented from deviating by more than 0.01 *HBW from its course. This may correspond to a threshold distance in the horizontal direction from the aisle rail of 0.01 *HBW.

[0037] The first and second guide wheel may be arranged at a distance of at least 1.02*HBWfrom each other.

[0038] The guide member of the aisle cart may comprise a protrusion protruding in a direction of an axis of the support wheel, the protrusion being configured to slide under a surface of the rack when the aisle cart travels on the aisle rail and to, by engaging the surface, prevent the aisle cart from jumping off the aisle rail, wherein the surface of the rack extends along the aisle in a direction of the aisle rail.

[0039] The axis of the support wheel may be an axis around which the support wheel rotates. The protrusion may prevent the support wheel of the aisle cart from being lifted more than a threshold distance above the hollow beam, the threshold distance being in the range of 1-15 mm (in particular 5 mm). The system may be configured such that the protrusion slides in parallel with the surface, when the aisle cart travels on the aisle rail. The system may be configured such that the protrusion slides at a distance in the range of 1- 15 mm (in particular 5 mm) under the surface, when the aisle cart travels on the aisle rail. Thus, the protrusion may slide freely, e.g. without any friction. The protrusion may engage the surface e.g. in the event of a collision which makes the aisle cart jump. In such a situation the protrusion may impact the surface and prevent the aisle cart from moving further away from the aisle rail.

[0040] The surface of the rack may be a bottom surface of a ledge extending in parallel with the hollow beam of the aisle rail. Alternatively, the surface of the rack may be a bottom surface of the hollow beam of the aisle rail. It may be advantageous to use a ledge extending in parallel with the hollow beam of the aisle rail. Such a ledge may be free from supporting structures underneath which may interfere with the protrusion. Thus, the protrusion may slide freely underneath the ledge without the risk of hitting a supporting structure. Thereby, the area underneath the hollow beam may be used for supporting structures that support the hollow beam. In a design where the protrusion slides under the bottom surface of the hollow beam the support structure for the hollow beam may be arranged at a first portion of the bottom surface of the hollow beam, leaving a second portion of the bottom surface of the hollow beam free for the protrusion to slide under.

[0041] An overlap between the ledge of the rack and the protrusion of the aisle cart may be at least 1 cm2. Such an overlap may be sufficient to safely prevent the aisle cart from jumping off the aisle rail. In particular, the overlap may be 10 cm2.

[0042] The protrusion may be a plate. The plate may be arranged in a horizontal plane.

[0043] Several guide members may be connected to form a set of guide members. Each guide member of the set of guide members may be associated with a direction in which the guide member prevents movements of the aisle cart. For example, the first guide wheel may prevent the aisle cart from turning right, relative to the aisle rail; and the second guide wheel may prevent the aisle cart from turning left, relative to the aisle rail, or vice versa. The protrusion may prevent the aisle cart from being lifted off the aisle rail. A first and a second guide wheel may form a set of guide members. Alternatively, a guide wheel and a protrusion may form a set of guide members. Advantageously, a first and a second guide wheel and a protrusion may form a set of guide members.

[0044] The aisle cart may comprise a connector, the connector connecting a chassis of the aisle cart to the protrusion and to at least one guide wheel. Thus, a set of guide members may be connected to the chassis of the aisle cart by the same connector. The connector may be strong enough to resist the forces that may be present when the aisle cart starts to deviate from the aisle rail. Using the same connector may save manufacturing cost as one single strong connector to a set of guide members may replace several strong connectors to individual guide members.

[0045] All guide members may be arranged on the same side of the aisle cart. This may facilitate easy deployment of the aisle cart on the aisle rail. For example, it may be easy to align the guide members with only one aisle rail when the aisle cart is placed on a pair of aisle rails. The aisle cart may comprise one set of guide members at a front portion of the aisle cart and one set of guide members at a rear portion of the aisle cart.

[0046] As previously mentioned, the hollow beam of the aisle rail may have a square or rectangular cross-section. Such a hollow beam may have a height of at least 60 mm and a width of at least 40 mm. Further, the height of the hollow beam may be below 200 mm. Further, the width of the hollow beam may be below 100 mm. In particular, the height of the hollow beam may be 120 mm and the width of the hollow beam may be 60 mm.

[0047] A wall thickness of the hollow beam may be at least 3 mm, e.g. 4 mm or 5 mm.

[0048] The hollow beam may have a yield stress of at least 100 N / m2, e.g. at least 300 N / m2. The hollow beam may have a yield stress in a range of 300- 700 N / m2.

[0049] The aisle rail may comprise a first and a second hollow beam, wherein both the first and the second hollow beam have square or rectangular crosssections, wherein the first and the second hollow beams are supported by a first and second plate, the first and second plate being arranged perpendicular to each other, the first plate being in contact with a respective bottom surface of the first and the second hollow beams, the second plate being in contact with a respective side surface of the first and the second hollow beams.

[0050] According to a second aspect, there is provided an aisle cart for transporting a row cart and an item along an aisle of a rack by travelling on an aisle rail of the rack, wherein the aisle rail comprises a hollow beam, the aisle cart comprising: a support wheel, being a wheel arranged to roll on a top surface of the hollow beam of the aisle rail and to support the aisle cart when the aisle cart travels on the aisle rail; and a guide member, being a member configured to guide the aisle cart along the hollow beam of the aisle rail by engaging the rack.

[0051] The guide member of the aisle cart may comprise a first guide wheel, being a wheel arranged to roll on a first side surface of the hollow beam; and / or a protrusion protruding in a direction of an axis of the support wheel, the protrusion being a protrusion for sliding under a surface of the rack when the aisle cart travels on the aisle rail, the surface of the rack being a bottom surface of a ledge extending in parallel with the hollow beam of the aisle rail.

[0052] According to a third aspect, there is provided a rack for storing an item, the rack comprising: an aisle; an aisle rail, being a rail extending along the aisle; and a plurality of rows, each row having a respective entrance at the aisle, wherein the rack is configured to allow transport of the item in the rack by an aisle cart and a row cart, wherein the aisle cart travels on the aisle rail and transports the row cart and the item to the entrance of a designated row and the row cart transports the item from the aisle cart, along the designated row, to a storage position in the designated row; wherein the aisle rail comprises a hollow beam having a top surface for a support wheel of the aisle cart to roll on when the aisle cart travels on the aisle rail.

[0053] The rack may further comprise a ledge for a protrusion of the aisle cart to slide under, the ledge extending in parallel with the hollow beam of the aisle rail.

[0054] Advantages of the second and third aspect are understood from the discussion of the first aspect.

[0055] BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise.

[0057] Fig. 1 illustrates a system for storing an item.

[0058] Fig. 2a-c illustrate an aisle cart, a row cart, aisle rail, and row rail.

[0059] Fig. 3 illustrates an aisle cart, a row cart, aisle rail, and row rail.

[0060] Fig. 4 illustrates an aisle cart.

[0061] Fig. 5 illustrates an aisle cart.

[0062] Fig. 6a-c illustrate an aisle cart, a row cart, and aisle rail,

[0063] Fig. 7 illustrates an aisle rail and a guide member.

[0064] Fig. 8 illustrates an aisle cart and aisle rail.

[0065] Fig. 9a-b illustrate an aisle rail.

[0066] Fig. 10 illustrates a row cart and row rail.

[0067] Fig. 11 illustrates a row rail.

[0068] Fig. 12 illustrates a bridge rail. Fig. 13 illustrates an aisle cart, a row cart, aisle rail, and row rail.

[0069] Fig. 14 illustrates a row rail.

[0070] Fig. 15 illustrates a bridge rail, a row rail, and a platform.

[0071] DETAILED DESCRIPTION

[0072] In cooperation with attached drawings, the technical contents and detailed description of the present invention are described thereinafter according to a preferable embodiment, being not used to limit the claimed scope. This invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

[0073] Fig. 1 illustrates a system 1 for storing an item 2. The system comprises a rack 10, the rack 10 comprises an aisle 20 and a plurality of rows 30. The illustrated rack 10 comprises three stories, each story comprising an aisle 20 and a plurality of rows 30. The aisle 20 extends in a first direction 11 and each row 30 extend in a second direction 12. In the figure, the first direction is the X direction and the second direction is the Y direction. It should be understood that the directions may be denoted differently. For example, in the FEM (European materials handling federation) standard, the direction in which the aisle extends (the first direction 11 ) is referred to as the X direction and the direction in which the rows extends (the second direction 12) is referred to as the Z direction, while the vertical direction is referred to as the Y direction.

[0074] Each row 30 comprises an entrance 35 and a far end 39. The entrance 35 of the row 30 being at the aisle 20 and the far end 39 being at the opposite end of the row 30.

[0075] In Fig. 1 , for clarity, the item 2 is not illustrated. However, the item 2 may be a pallet 3, with or without goods 4. Alternatively, the item 2 may be any form of goods 4, crate or box. The rack 10 of Fig. 1 is suitable to store items 2 in the form of pallets 3, with or without goods 4.

[0076] The system 1 further comprises an aisle cart 40, and a row cart 60. The aisle cart 40 and row cart 60 are configured to transport the item 2 to a storage position 16 in a designated row 30, e.g. from a loading position 14 to the storage position 16. The storage position 16 may be any position along the designated row 30. The designated row 30 may be any row 30 of the plurality of rows 30.

[0077] In the following, the top story of the rack 10 in Fig. 1 will be discussed as an illustrative example. The top story of the rack 10 comprises an aisle 20 and a plurality of rows 30. The aisle 20 extends in the X direction, starting at a loading position 14 at the at the edge of the rack 10. A plurality of rows 30 extend to the left (in the positive Y direction) and to the right (in the negative Y direction) of the aisle 20. Each row 30 has an entrance 35 at the aisle 20. In Fig. 1 , an aisle cart 40 is seen in the aisle 20 of the top story of the rack 10. A row cart 60 is seen in the first row 30 to the right of the top story of the rack 10. As mentioned, the storage position 16 may be any position along the designated row 30, e.g. a position furthest from the entrance 35 of the row 30 which is free to accept the item 2. A storage position 16 is indicated in the last row 30 to the left of the aisle 20 of the top story of the rack 10 in Fig. 1 . Since said row 30 is empty in the figure, the storage position may be at the far end 39 of said row 30.

[0078] The far end 39 of the rows 30 may be arranged to allow the row cart 60 being: received by the row cart 60 being lowered onto the row rail 32; and / or collected by the row cart 60 being lifted off the row rail 32.

[0079] For example, the far end 39 may be open, such that a fork lift or an elevator may deliver the row cart at the far end of the row rail 32. Thus, row carts 32 (e.g. empty row carts 32) may be delivered into (or retrieved from) the rack 10 without having to take the path through the aisle 20. Thus, congestion in the rack 10 may be avoided.

[0080] Further, as illustrated in Fig. 1 , a row 30 may, at the far end 39, be free from horizontal support elements connecting the row rails of the pair of row rails, within a distance from the outermost point of the row rails. This is for example seen at the marked storage position 16. The distance may be 0.5 m or 1 m. Alternatively, the distance may be equal or larger than the length of the row cart (not shown). Thus, a row cart supported from below by e.g. the fork of a forklift may be lifted into the row without the fork being obstructed by a horizontal support element.

[0081] Figs 2a-c illustrate the aisle cart 40 arriving at a designated row 30 and the row cart 60 moving into the designated row 30. Again, for clarity, the item 2 is not illustrated. The illustrated aisle 20 comprises a rail 22 (henceforth called aisle rail 22). In the illustrations, the aisle rail 22 is in the form of a hollow beam 50. As illustrated, there may be a pair of aisle rails 22. The aisle cart 40 may comprise a wheel 46 (also called support wheel 46 of the aisle cart 40) for rolling on the aisle rail 22. The aisle cart 40 may comprise two pairs of support wheels 46.

[0082] In Figs 2a-c, there is one row 30 to the left of the aisle 20 and one row 30 to the right of the aisle 20, with a respective entrance 35 at the aisle 20. Each illustrated row 30 comprises a rail 32 (henceforth called row rail 32). As illustrated, each row 30 may comprise a pair of row rails 32. The row cart 60 may comprise a wheel 66 (also called support wheel 66 of the row cart 60) for rolling on the row rail 32. The row cart 60 may comprise two pairs of support wheels 66.

[0083] The illustrated aisle cart 40 comprises a platform 42. The platform 42 is best seen in Fig. 2b and Fig. 2c, and in the insets of Fig. 2a and Fig. 2b. The illustrated platform 42 is configured to support the at least one wheel 66 of the row cart 60 while the aisle cart 40 transports the row cart 60, the platform 42 being displaceable relative to the at least one wheel 46 of the aisle cart 40. As illustrated, the aisle cart 40 may further comprise a belt conveyor 52 for pulling the item 2 onto the aisle cart 40 and supporting the item 2 while the aisle cart 40 transports the item 2, the belt conveyor 52 being attached to the platform 42 and configured to be displaced relative to the at least one wheel 46 of the aisle cart 40 together with the platform 42.

[0084] When the aisle cart 40 transports the row cart 60 and the item 2 along the aisle 20, the row cart 60 may stand on the platform 42 under the item 2. When the aisle cart 40 transports the row cart 60 and the item 2 along the aisle 20, the item 2 may stand on the belt conveyor 52. However, the aisle cart 40 does not necessarily need to comprise a belt conveyor 52. For example, when the aisle cart 40 transports the row cart 60 and the item 2 along the aisle 20, the item 2 may stand on the row cart 60, or on a support surface of the aisle cart 40, instead of on the belt conveyor 52.

[0085] The row cart 60 and the item 2 may be transported along the aisle 20 using the aisle cart 40. The aisle cart 40 may be stopped at the entrance 35 of the designated row 30, this is illustrated in Fig. 2a. The platform 42 may then be displaced, relative to the at least one wheel 46 of the aisle cart 40, in the second direction 12 such that a gap 36 between the platform 42 and the entrance 35 of the designated row 30 is reduced. Fig. 2a illustrates a gap 36 between the platform 42 and the entrance 35 of the designated row 30.

[0086] Fig. 2b illustrates the platform 42 of the aisle cart 40 being displaced towards the entrance 35 of the designated row. In the figure, the row cart 60 is not displaced for reasons of clarity, such that the platform 42 is visible. In reality, the row cart 60 standing on the platform 42 would be displaced together with the platform 42. Fig. 2b further shows the gap 36 between the platform 42 and the rolling surface 81 (a.k.a. lower horizontal surface 81) of the row rail 32 being closed.

[0087] The row cart 60 may then move into the designated row 30 by rolling from the platform 42, across the gap 36, and onto the rolling surface 81 of the row rail 32. This is illustrated in Fig. 2c. Part of the row rail 32 has been cut away for illustrative purposes, such that a wheel 66 of the row cart 60 can be seen rolling on the rolling surface 81 of the row rail 32.

[0088] In Fig. 2c, the row cart 60 is not carrying an item 2. This is for illustrative purposes. However, the row cart 60 may carry an item 2, e.g. resting on-top of the row cart 60. Thus, the row cart 60 may transfer the item 2 into the designated row, when the at least one wheel 66 of the row cart 60 crosses the reduced gap 36.

[0089] Before the row cart 60 transfers the item 2 into the designated row 30, the row cart 60 may lift the item using a lifting device 62. The lifting device 62 may be a raisable platform, e.g. part of the chassis of the row cart 60. Thus, the item 2 may be lifted up, e.g. from the belt conveyor 52, of the aisle cart 60. The lifting device 62 may be configured to lift the item 2 by lowering the wheels 66 of the row cart 60, e.g. lowering the wheels 66 of the row cart 60 relative to the chassis of the row cart 60. In other words, a separation between the wheels 66 of the row cart 60 and the chassis of the row cart 60 may be increased to lift the item 2.

[0090] After the row cart 60 has transferred the item 2 into the designated row 30, the row cart 60 may transport the item 2 along the designated row 30. The row cart 60 may then place the item 2 at the storage position 16 in the designated row 30.

[0091] The inset of Fig. 2a and the inset of Fig. 2b show a top view of the aisle cart 40 at the entrance 35 of the designated row 30 before and after displacing the platform 42, respectively. Thus, the insets of Fig. 2a Fig. 2b illustrate the gap 36 being reduced. The gap 36 in the inset of Fig. 2a may be 85 mm. The gap 36 in the inset of Fig. 2b may be 5 mm. The insets of Fig. 2a and Fig. 2b illustrate the gap 36 extending between a first edge 43 of the platform 42 and a first edge 33 of the row rail 32. Further, the insets of Fig. 2a and Fig. 2b illustrate that the first edge 33 of the rail 32 may be arranged at an angle to the second direction 12 and that the first edge 43 of the platform 42 may be arranged at an angle to the second direction 12. The system 1 may be configured such that both the angle of the first edge 33 of the rail 32 and the angle of the first edge 43 of the platform 42 are larger or smaller than 90°, as illustrated. The angle of the first edge 33 of the rail 32 may have an absolute value in the range 10°-80°, e.g. 30°-60°. The angle of the first edge 43 of the platform 42 may have an absolute value in the range 10°-80°, e.g. 30°-60°. The angle of the first edge 33 of the rail 32 may be the same as the angle of the first edge 43 of the platform 42, as illustrated.

[0092] The platform 42 may be displaceable both forwards and backwards. While Figs 2a-c illustrate the platform 42 being displaced towards a row 30 to the right of the aisle 20 (as compared to the first direction 11 ), Fig. 3 illustrate the platform 42 being displaced towards a row 30 to the left of the aisle 20 (as compared to the first direction 11 ).

[0093] Fig. 4 is a side view of an aisle cart 40 carrying an item 2 in the form of a pallet 3 with goods 4. In Fig. 4, the pallet 3 is standing on the belt conveyor 52. For illustrative purposes the row cart 60 is not shown. However, the row cart 60 may stand on the platform 42 of the aisle cart 40, underneath the pallet 3.

[0094] Fig. 13 shows an aisle cart 40 at a designated row 30, in this case the row 30 to the right of the aisle 20 (as compared to the first direction 11 ). In the figure, the platform 42 is displaced towards the designated row 30 and the row cart 60 is entering the designated row 30. The row cart 60 may (as in Fig. 13) enter the designated row 30 empty, when collecting an item 2, e.g. the item 2 closest to the aisle 20. Alternatively, the row cart 60 may enter the designated row 30 while carrying an item 2 to be stored in the designated row 30. Fig. 13 further illustrates items 2 in the form of pallets 3 with goods 4 stored both in the row 30 to the left of the aisle 20 and in the row 30 to the right of the aisle 20.

[0095] Fig. 5 shows an aisle cart 40 comprising a first 42’ and a second 42” platform, the first platform 42’ being configured to support a left side wheel of the row cart 60 and the second platform 42” being configured to support a right side wheel of the row cart 60. The first 42’ and second 42” platform are separated by an open space 148. As seen in the figure, both the first 42’ and second 42” platform are displaceable relative to the at least one wheel 46 of the aisle cart 40. In the figure, both the first 42’ and second 42” platform have been displaced in the negative Y direction, towards the viewer. A platform 42 of the aisle cart 40 may be displaced by displacement means 58. The first 42’ and second 42” platform may be displaceable by a common displacement means 58, as illustrated. Displacement means 58 may comprise a motor of any sort (e.g. a stepper motor) or an actuator (e.g. a linear actuator). Alternatively or additionally, the displacement means 58 may comprise a hydraulic actuator or pneumatic actuator.

[0096] Fig. 5 further shows that the belt conveyor 52 may be attached to the platform 42 and configured to be displaced relative to the at least one wheel 46 of the aisle cart 40 together with the platform 42. The illustrated aisle cart 40 further comprises a motor 54 for driving the belt conveyor 52. Part of the aisle cart 40 in Fig. 5 is removed for illustrative purposes, to show the motor 54. The motor 54 may be immovably attached to the chassis 56 of the aisle cart 40 such that the motor 54 is prevented from being displaced relative to the at least one wheel 46 of the aisle cart 40. The aisle cart 40 may be configured to: drive the belt conveyor 52 by the motor 54 while the platform 42 is displaced relative to the at least one wheel 46 of the aisle cart 40; or declutch the belt conveyor 52 from the motor 54 before or while the platform 42 is displaced relative to the at least one wheel 46 of the aisle cart 40.

[0097] In Fig. 5, the aisle cart 40 comprises blocking elements 47, each blocking element 47 being a movable element which: in a blocking position, blocks the row cart 60 from leaving the platform 42; and in an unblocking position, unblocks the row cart 60 from leaving the platform 42. In Fig. 5 there are two blocking elements 47 at each side of the aisle cart 40. Each illustrated blocking element 47 is a lever pivotably attached to the platform 42. The aisle cart 40 may be configured to move the blocking element 47 from the blocking position to the unblocking position such that the blocking element 47 arrives at the unblocking position after the platform 42 has started displacing relative to the at least one wheel 46 of the aisle cart 40. In Fig. 5, the first 42’ and second 42” platform have been displaced in the negative Y direction, towards the viewer. In Fig. 5 the blocking elements 47 at the end of the platforms 42’, 42” towards the viewer are in the unblocking position wherein the lever 47 has pivoted downwards (out of a slit 49). Thus, said blocking elements 47 are not blocking the travel path of the row cart.

[0098] In Fig. 5 the blocking elements 47 at the end of the platforms 42’, 42” away from the viewer are in the blocking position wherein the lever 47 has not pivoted downwards (out of a slit 49). Thus, said blocking elements 47 are blocking the travel path of the row cart.

[0099] In other words, in Fig. 5, a row cart 60 may move out of the aisle cart 40 in the negative Y direction but not in the positive Y direction.

[0100] Figs 6a-c illustrate that the aisle cart 40 may comprise a guide member 110. Fig. 6a shows an aisle cart 40 on aisle rail 22 in the form of hollow beams 50. The support wheels 46 of the aisle cart 40 roll on the top surfaces 54t of the respective hollow beams 50 of the aisle rail 22. The illustrated aisle cart 40 comprises a guide member 110, being a member configured to guide the aisle cart 40 along the hollow beam 50 of the aisle rail 22 by engaging the rack 10. As illustrated, the aisle cart 40 may comprise several guide members 110. Fig. 6b and Fig. 6c show close-up views of the frontmost guide member 110 in Fig. 6a, as seen from different perspectives. The illustrated guide member 110 has three different means for engaging the rack 10, a first guide wheel 111 , a second guide wheel 112, and a protrusion 113. However, it should be understood that either one could be used on its own or in any combination with the others.

[0101] In Figs 6a-c, the guide member 110 comprises a first guide wheel 111 , being a wheel arranged to roll on a first side surface 51s of the hollow beam 50 and a second guide wheel 112, being a wheel arranged to roll on second side surface 52s of the hollow beam 50, the second side surface 52s of the hollow beam 50 being opposite to the first side surface 51s of the hollow beam 50. The first side surface 51s of the hollow beam 50 may be the outer side surface of the hollow beam while the second side surface 52s of the hollow beam 50 is the inner side surface of the hollow beam, as illustrated, or vice versa.

[0102] In Figs 6a-c, the guide member 110 comprises a protrusion 113 protruding in a direction of an axis 46A of the support wheel 46. The illustrated protrusion 113 is a plate.

[0103] Fig. 8 illustrates that the protrusion 113 may slide under a surface 10s of the rack 10 when the aisle cart 40 travels on the aisle rail 22. In Fig. 8 said surface 10s of the rack 10 is a bottom surface 70s of a ledge 70 extending in parallel with the hollow beam 50 of the aisle rail 22. Thus, the protrusion 113 is configured to engage a portion 17 of the rack (in this case the ledge 70) that extends in parallel with the hollow beam 50 of the aisle rail 22 of the rack 10.

[0104] The protrusion 113 may be arranged at a distance below the ledge 70, said distance may be 1-15 mm, e.g. 5 mm. The protrusion 113 may extend 20 mm under the ledge 70, in a horizontal direction perpendicular to the ledge. The protrusion 113 may extend 50 mm under the ledge 70, in a horizontal direction parallel to the ledge.

[0105] Fig. 7 illustrates a close-up view of the guide member 110 engaging the hollow beam 50 by the first 111 and second 112 guide wheel. A spacing between the first 111 and second 112 guide wheel may be larger than the width of the hollow beam 50, e.g. 2% larger than the width of the hollow beam 50.

[0106] Fig. 7 and Fig. 6c shows a connector 48 for connecting the chassis 56 of the aisle cart 40 to the protrusion 113 and to the first 111 and second 112 guide wheel. The connector 48 may e.g. comprise one or more bars or rods, e.g. made of steel.

[0107] Figs 9a-b illustrate that an aisle rail 22 may comprise a plurality of hollow beams 50. Fig. 9a and 9b are views of the same aisle rail 22, as seen from opposite sides.

[0108] Fig. 9a-b illustrate a section of an aisle rail 22 comprising a first 50’ and a second 50” hollow beam. The joint between the first 50’ and a second 50” hollow beam may be smooth.

[0109] In Fig. 9a-b, the first 50’ and the second 50” hollow beams are supported by a first 55 and second 56 plate, the first 55 and second 56 plate being arranged perpendicular to each other, the first plate 55 being in contact with a respective bottom surface 53b of the first 50’ and the second 50” hollow beams, the second plate 56 being in contact with a respective side surface 52s of the first 50’ and the second 50” hollow beams. Similar first 55 and second 56 plates are also seen in Fig. 6c.

[0110] Fig 10 illustrate a row cart 60 on row rail 32, in a cross-sectional view of the row rail 32. In other words, the row cart is standing in a row 30. A left and a right support wheel 66 of the row cart 60 are standing on respective row rails 32. The illustrated row rail 32 comprise a upper metal sheet 87 and a lower metal sheet 85, both being arranged horizontally. A side metal sheet 86 is arranged to connect the upper metal sheet 87 with the lower metal sheet 85. A protruding metal sheet 84 protrudes downwards from the lower metal sheet 85. In Fig. 10 an item 2, in the form of a pallet 3, is resting (i.e. supported) on the respective upper metal sheets 87 of the left and right row rail 32. Thus, the pallet is stored 3 on the row rail 32. The support wheels 66 of the row cart 60 are supported by the respective lower metal sheets 85 of the left and right row rail 32. The illustrated row cart 60 comprises a lifting device 62. In Fig. 10 the lifting device 62 is in a lowered position. Thus, the row cart may travel under the stored item 2. By raising the lifting device 62, the row cart 60 may lift the item 2 from the row rail 32.

[0111] The row cart 60 of Fig. 10 comprises guide members 120 configured to guide the row cart 60 onto the row rail 32 by engaging the side surface 183 of the row rail 32. In this case, the side surface 183 is a surface of the side metal sheet 86. The guide member 120 may be a guide wheel.

[0112] Fig 11 is a cross-sectional view of a row rail 32, corresponding to the left row rail 32 of Fig. 10. As described above, the illustrated row rail 32 comprises a upper metal sheet 87, a side metal sheet 86, a lower metal sheet 85, and a protruding metal sheet 84.

[0113] The illustrated row rail 32 comprises an upper horizontal surface 82 for supporting the item 2, the upper horizontal surface 82 being a surface of the illustrated upper metal sheet 87.

[0114] The illustrated row rail 32 comprises a lower horizontal surface 81 for a wheel 66 of the row cart 60 to travel on, the lower horizontal surface 81 being a surface of the illustrated lower metal sheet 85.

[0115] In the figure, the upper horizontal surface 82 comprise an outer side 82o and an inner side 82i. Similarly, the lower horizontal surface 81 comprise an outer side 81 o and an inner side 81 i.

[0116] The illustrated row rail 32 comprises a side surface 183, the side surface 183 being a surface of the side metal sheet 86. The illustrated side surface 183 is a flat inclined surface 83.

[0117] In Fig. 11 , the outer side 81 o of the lower horizontal surface 81 is connected to the inner side 82i of the upper horizontal surface 82 by the side surface 183. Further, in Fig. 11 , the inner side 82 i of the upper horizontal surface 82 is further away from the center axis of the row 30 than the outer side 81 o of lower horizontal surface 81 .

[0118] In Fig. 11 , the upper metal sheet 87, the side metal sheet 86, the lower metal sheet 85, and the protruding metal sheet 84 form a single metal sheet. Fig. 11 further illustrates a row rail supporting bracket 130.

[0119] The illustrated row rail supporting bracket 130 comprises a first plate 131 arranged horizontally and supporting a back side 85b of a lower metal sheet 85 of the row rail 32.

[0120] The illustrated row rail supporting bracket 130 further comprises a second plate 132 supporting a back side 86b of the side metal sheet 86.

[0121] The illustrated row rail supporting bracket 130 further comprises a third plate 133. The third plate 133 may be fastened to the protruding metal sheet 84 by a fastener (not shown), e.g. a fastener in the form of a bolt, a screw, or a rivet.

[0122] Fig. 14 is a perspective view of a row rail 32 similar to the row rails 32 of Figs 10 and 11.

[0123] The illustrated row rail 32 comprises an upper horizontal surface 82 for supporting the item 2, the upper horizontal surface 82 being a surface of the illustrated upper metal sheet 87.

[0124] The illustrated row rail 32 comprises a lower horizontal surface 81 for a wheel 66 of the row cart 60 to travel on, the lower horizontal surface 81 being a surface of the illustrated lower metal sheet 85.

[0125] The illustrated row rail 32 comprises a side surface 183, the side surface 183 being a surface of the side metal sheet 86. The illustrated side surface 183 is a flat inclined surface 83.

[0126] The illustrated row rail 32 further comprises a protruding metal sheet 84.

[0127] Fig 12 is a close-up view of the row rail 32 at the entrance 35 of the row 30. As illustrated, the row rail 32 may comprise a bridge rail 90 forming a bridge for the row cart 60 to travel across. The bridge rail 90 may be part of the row rail 32. Thus, the row cart 60 may travel across the bridge rail 90 onto a further section of the row rail 32. Thus, the row rail 32 may be produced in a number of long sections which may be connected to form most of the row rail 32. The bridge rail 90 may then be a short section of the row rail 32 which acts as an adaptor for easing the transfer of the row cart 60 from the aisle cart 40 into the row 30.

[0128] The illustrated bridge rail 90 comprises a horizontal surface 81 for the wheel 66 of the row cart 60 to travel on. The illustrated bridge rail 90 has a first end 95 close to the aisle 20 and a second end 96 further away from the aisle. The horizontal surface 81 of the illustrated bridge rail 90 may be wider at the first end 95 than at the second end 96.

[0129] The horizontal surface 81 of the illustrated bridge rail 90 comprises an edge 33 facing the aisle 20, wherein an angle of the edge 33 deviates from 90°.

[0130] The illustrated bridge rail 90 comprises a side surface 183. An angle between the side surface 183 of the bridge rail 90 and the horizontal surface 81 of the bridge rail 90 may be smaller in a first cross-section of the bridge rail 90 than in a second cross section of the bridge rail 90. The first cross-section of the bridge rail 90 may be at the first end 95. The second cross-section of the bridge rail 90 may be at the second end 96.

[0131] Fig. 15a-e illustrate a row rail 32 and a platform 42 of an aisle cart 40. For clarity, the rest of the aisle cart 40 is not shown. The row rail 32 comprising a bridge rail 90 for the row cart 60 to travel across. Fig. 15a is a perspective view. Fig. 15b is a cross-sectional view of the platform 42. Fig. 15c is a cross-sectional view of the bridge rail 90 at a first end 95 close to the aisle 20. Fig. 15d is a cross-sectional view of the bridge rail 90 at a second end 96 close to the aisle 20 further away from the aisle 20. Fig. 15e is a cross-sectional view of the row rail 32 at a section adjacent to the bridge rail 90.

[0132] In the Fig. 15e cross-sectional view of the row rail 32, the row rail 32 comprises an upper horizontal surface 82, for supporting the item 2, and a lower horizontal surface 81 , for a wheel 66 of the row cart 60 to travel on. The inner side of the upper horizontal surface 82 is further away from the center axis of the row 30 than the outer side of lower horizontal surface 81 . The upper horizontal surface 82 and the lower horizontal surface 81 are connected by a side surface 183, which is inclined.

[0133] In the Fig. 15b cross-sectional view of the platform 42, the platform 42 is connected to a side surface 283 which is in the illustration is vertical.

[0134] In the Fig. 15c-d cross-sectional views of the bridge rail 90, it is seen that the bridge rail 90 may act as an adaptor between the platform 42 and the further section of the row rail 32. In the cross-sectional view of the bridge rail 90 at the first end 95, Fig. 15c, the cross-section of the bridge rail 90 is similar to the cross-section of the platform 42 and the side surface 283 connected to the platform 42, seen in Fig. 15b. Further, in the cross-sectional view of the bridge rail 90 at the second end 96, Fig. 15d, the cross-section of the bridge rail 90 is similar to the cross-section of the further section of the row rail 32 in Fig. 15e. Thus, the horizontal surface 81 of the bridge rail 90 is wider at the first end 95 than at the second end 96. Further, an angle between the side surface 183 of the bridge rail 90 and the horizontal surface 81 of the bridge rail 90 is smaller at the cross-section at the first end 95 than at the second end 96. As seen in the figures, the angle (with respect to the direction of the row 30) of the first edge 33 of the bridge rail 90 and the angle (with respect to the direction of the row 30) of the first edge 43 of the platform 42 may both differ from 90°. Said angles may e.g. be the same.

[0135] In the above the inventive concept has mainly been described with reference to a limited number of examples. However, as is readily appreciated by a person skilled in the art, other examples than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims

CLAIMS1 . A system (1 ) for storing an item (2), the system (1 ) comprising a rack (10), an aisle cart (40) and a row cart (60), the rack (10) comprising: an aisle (20); an aisle rail (22), being a rail extending along the aisle (20); and a plurality of rows (30), each row (30) having a respective entrance at the aisle (20); the aisle cart (40) being a cart configured to travel on the aisle rail (22) and to transport the row cart (60) and the item (2) to the entrance of a designated row (30); the row cart (60) being a cart configured to transport the item (2) from the aisle cart (40), along the designated row (30), to a storage position (16) in the designated row (30); wherein the aisle rail (22) comprises a hollow beam (50); wherein the aisle cart (40) comprises a support wheel (46), being a wheel arranged to roll on a top surface (54t) of the hollow beam (50) of the aisle rail (22) and to support the aisle cart (40) when the aisle cart (40) travels on the aisle rail (22); and a guide member (110), being a member configured to guide the aisle cart (40) along the hollow beam (50) of the aisle rail (22) by engaging the rack (10).

2. The system (1 ) of claim 1 , wherein the guide member (110) is configured to engage the hollow beam (50) of the aisle rail (22) of the rack (10); and / or engage a portion (17) of the rack (10) that extends in parallel with the hollow beam (50) of the aisle rail (22) of the rack (10).

3. The system (1 ) of claim 1 or 2, wherein the guide member (110) of the aisle cart (40) comprises a first guide wheel (111 ), being a wheel arranged to roll on a first side surface (51s) of the hollow beam (50).

4. The system (1 ) of claim 3, wherein the guide member (110) of the aisle cart (40) comprises a second guide wheel (112), being a wheel arranged to roll on second side surface (52s) of the hollow beam (50), the second side surface (52s) of the hollow beam (50) being opposite to the first side surface (51s) of the hollow beam (50).

5. The system (1 ) of any one of the preceding claims, wherein the guide member (110) of the aisle cart (40) comprises a protrusion (113) protruding in a direction of an axis (46A) of the support wheel (46), the protrusion (113) being configured to slide under a surface (10s, 70s) of the rack (10) when the aisle cart (40) travels on the aisle rail (22) and to, by engaging the surface (10s, 70s), prevent the aisle cart (40) from jumping off the aisle rail (22), wherein the surface (10s, 70s) of the rack (10) extends along the aisle (20) in a direction of the aisle rail (22).

6. The system (1 ) of claim 5, wherein the surface (10s, 70s) of the rack (10) is a bottom surface (70s) of a ledge (70) extending in parallel with the hollow beam (50) of the aisle rail (22).

7. The system (1 ) of claim 6, wherein an overlap between the ledge (70) of the rack (10) and the protrusion (113) of the aisle cart (40) is at least 1 cm2.

8. The system (1 ) of any one of the preceding claims, wherein the aisle cart (40) comprises a connector (48), the connector (48) connecting a chassis (56) of the aisle cart (40) to the protrusion (113) according to any one of claims 5-7 and to at least one guide wheel (111 , 112) according to claim 3 or 4.

9. The system (1 ) of any one of the preceding claims, wherein the hollow beam (50) of the aisle rail (22) has a square or rectangular cross-section.

10. The system (1 ) of claim 9, wherein the hollow beam (50) has a height of at least 60 mm and a width of at least 40 mm.11 . The system (1 ) of any one of the preceding claims, wherein the hollow beam (50) has a yield stress of at least 100 N / m212. The system (1 ) of claim 10 or 11 , wherein the aisle rail (22) comprises a first (50’) and a second (50”) hollow beam, wherein both the first (50’) and the second (50”) hollow beam have square or rectangular cross-sections, wherein the first (50’) and the second (50”) hollow beams are supported by a first (55) and second (56) plate, the first (55) and second (56) plate being arranged perpendicular to each other, the first plate (55) being in contact with a respective bottom surface (53b) of the first (50’) and the second (50”) hollow beams, the second plate (56) being in contact with a respective side surface of the first (50’) and the second (50”) hollow beams.

13. An aisle cart (40) for transporting a row cart (60) and an item (2) along an aisle (20) of a rack (10) by travelling on an aisle rail (22) of the rack (10), wherein the aisle rail (22) comprises a hollow beam (50), the aisle cart (40) comprising: a support wheel (46), being a wheel arranged to roll on a top surface (54t) of the hollow beam (50) of the aisle rail (22) and to support the aisle cart (40) when the aisle cart (40) travels on the aisle rail (22); and a guide member (110), being a member configured to guide the aisle cart (40) along the hollow beam (50) of the aisle rail (22) by engaging the rack (10).

14. The aisle cart (40) of claim 13, wherein the guide member (110) of the aisle cart (40) comprises a first guide wheel (111 ), being a wheel arranged to roll on a first side surface (51s) of the hollow beam (50); and / or a protrusion (113) protruding in a direction of an axis (46A) of the support wheel (46), the protrusion (113) being a protrusion for sliding under a surface (10s, 70s) of the rack (10) when the aisle cart (40) travels on the aisle rail (22), the surface (10s, 70s) of the rack (10) being a bottom surface (70s) of a ledge (70) extending in parallel with the hollow beam (50) of the aisle rail (22).

15. A rack (10) for storing an item (2), the rack (10) comprising: an aisle (20); an aisle rail (22), being a rail extending along the aisle (20); and a plurality of rows (30), each row (30) having a respective entrance at the aisle (20),wherein the rack (10) is configured to allow transport of the item (2) in the rack (10) by an aisle cart (40) and a row cart (60), wherein the aisle cart (40) travels on the aisle rail (22) and transports the row cart (60) and the item (2) to the entrance of a designated row (30) and the row cart (60) transports the item (2) from the aisle cart (40), along the designated row (30), to a storage position (16) in the designated row (30); wherein the aisle rail (22) comprises a hollow beam (50) having a top surface (54t) for a support wheel (46) of the aisle cart (40) to roll on when the aisle cart (40) travels on the aisle rail (22).

16. The rack (10) of claim 15, wherein the rack (10) further comprises a ledge (70) for a protrusion (113) of the aisle cart (40) to slide under, the ledge (70) extending in parallel with the hollow beam (50) of the aisle rail (22).

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