Field of the invention

[0001] The invention relates to an overhead crane for hoisting and moving containers, comprising a rail track which rests on the ground by means of columns, and a frame which is displaceable along the rail track and is provided with means for picking up and hoisting containers. The invention also relates to an assembly of at least two overhead cranes.

[0002] The invention also relates to a vehicle, in particular an Automated Guided Vehicle, in particular an Automated Guided Vehicle configured to transport containers, such as standardized containers for transport over sea or land. Background of the invention

[0003] An overhead crane for hoisting and moving containers can be used in both sea port container terminals and inland port terminals. A sea port container terminal usually comprises three areas. A strip, which is situated directly on the water and has a width of approximately 50 metres, is also referred to as the ship to shore (STS) area. This is the area in which the containers are transferred from the oceangoing vessels which have entered the harbour onto land using the large cranes on board, also referred to as STS cranes.

[0004] Directly behind the STS area, on the landward side of the STS area, there is a transfer zone where the containers are taken to a storage yard by means of so- called straddle carriers or automated guided vehicles (AGV's). This area is approximately 100 to 120 metres wide. The storage yard is also referred to as the stack area.

[0005] Depending on the size of the terminal and the transportation means, the width of the stack area varies between 300 and 700 metres. The length of the stack area is usually equal to the length of the quayside.

[0006] Over the course of the last 20 years, the loading and unloading speed of the STS cranes has steadily increased in order to ensure that the vessels are moored on the quayside for as short a time as possible. This has resulted in congestion in or just in front of the stack area, requiring the creation of intermediate buffers. [0007] It is an object of the invention to increase the processing speed in the stack area compared to the current situation. It is another object of the invention to increase the stacking capacity while not increasing the surface area. A greater stack density saves valuable space. Stacking the containers higher does increase the stack density, but, with the crane systems which are currently being used in the stack area, the so-called stack crane systems, it is disadvantageous in terms of the time ("digging time") which is spent when containers from the bottom layers have to be transported first.

[0008] The stacking height of stacks of containers which are transported across the terminal using straddle carriers is usually 1 over 3. This means that the stack comprises three layers and that there is one layer which is reserved for transport movements above these.

[0009] With cranes which are known as rail-mounted gantry cranes (RMGs), i.e. cranes which may be defined as gantry cranes travelling on rails which have been laid at ground level, the stacking height is already 1 over 4 or even 1 over 6, despite the abovementioned drawback of the increasing "digging time".

[0010] For the sake of completeness, it should be noted that the effective processing speed in a stack is determined to a significant degree by the number of cranes, the speed of the cranes, both when travelling and when hoisting, the stack density, the degree of automation, the susceptibility to failure, the redundancy and the length-to- width-ratio of the stack lanes.

[0011] As has been indicated above, the cranes in the stack areas of container terminals are often configured as RMGs which travel on rail systems which have been installed at ground level. These RMGs have the drawback that they cannot pass each other, so that the working area of an RMG is linked to the seaward side or the landward side of a terminal. Another drawback is the fact that the gantry structure has a considerable dead load and therefore it requires a large amount of power to drive the crane. It is quite common to use a dead weight of 150 tonnes to transport a container weighing 30 tonnes. Furthermore, the travelling speed is limited, as the centre of gravity is situated high above the wheels, which is disadvantageous for both the longitudinal stability and the transverse stability and the swinging of the load during transportation.

[0012] In order to enable RMGs to pass each other in one lane (also referred to as a track) of the stack area, according to the prior art, an oversized RMG is added which also serves as a replacement in case one of the other RMGs fails. The drawback of this solution is that the additional rail system to accommodate the oversized RMG takes up a great deal of space along the entire length of the lane. Another drawback is the fact that the workload during normal operation is lower for each RMG than is the case with two RMGs in one lane. In lanes with two RMGs, a problem again arises when one of the two RMGs fails, since the RMGs cannot pass each other. In order to solve this problem, a so-called rescue crane has been developed for the current situation, which can be used to pick up a broken-down RMG and move it..

[0013] Automated Guided Vehicles (AGVs) are vehicles that can automatically move along predetermined paths. AGVs that are in use in container terminals for carrying cargo containers, for example from a ship unloading area of the terminal to a storage area of the terminal, typically have a relatively large own weight and can usually only change direction using relatively large arcs of turning. I n other words, when a known AGV changes direction, a relatively large area must be available for the AGV to make the turn. This is due to the fact that most AGVs tend to have only one set of steerable wheels and a relatively large length (which length is required by the standard container sizes).

[0014] Known AGVs are thus typically built like trucks using heavy materials such as metals to provide enough strength to support itself and any containers. The AGVs have large air-pressured rubber tires as used in trucks or cranes. The contact between these tires and the supporting surface causes friction.

[0015] Known AGVs typically drive on a flat surface without any further structure. They must frequently stop and wait for other crossing traffic, which costs time and is prone to accidents.

[0016] It is a further object of this invention to provide an improved vehicle for carrying a load. It is a further object of this invention to provide a vehicle that can be built using relatively light-weight materials.

Summary of the invention

[0017] The invention is aimed at increasing the processing speed in the stack area using overhead cranes, which can generally achieve much greater speeds of travel than RMGs. I n particular, the invention provides an overhead crane whose frame is a truss frame which can accommodate at least one container completely. The invention also provides an assembly of at least two overhead cranes with a truss frame, in which the rail tracks of the overhead cranes extend substantially parallel to each other at different levels with respect to the ground, and rest on the ground by means of common columns. [0018] Due to the fact that with the overhead crane according to the invention, the containers can be hoisted completely inside the frame, to which end the frame is open on the underside, it is possible to transport the containers over one another at a very short distance apart in the horizontal plane in the assembly of overhead cranes. In this case, it is also possible for the overhead cranes to pass each other in one and the same lane in the same or opposite direction of travel.

[0019] The overhead crane according to the invention can be configured in two main configurations, namely with a truss frame which has upper truss girders, above the level of the rail track, and with a truss frame which has lower truss girders, below the level of the rail track. The truss frame with upper truss girders can be configured to have an overhang on one or two sides. Irrespective of the configuration of the overhead crane which is selected, the truss frames are preferably configured in such a manner that, in case of failure, one crane can pick up the frame of the other crane and move it outside the work area.

[0020] In summary, the following advantages and further aspects of the invention can be mentioned.

[0021] The overhead cranes can pass each other in the same lane, both in the empty and in the loaded state.

[0022] The containers can be hoisted until they are completely within the frame of the overhead crane. As a result thereof, it is possible to transport containers over one another at a very short distance apart in the horizontal plane.

[0023] Each overhead crane can pick up the frame of another crane and take it to another location.

[0024] If an overhead crane with a frame of upper truss girders is used as the highest crane, containers can be stacked to virtually the same height as the height of the upper crane track beams which define the rail track for said crane. The columns can thus be made lower than is the case with a conventional overhead crane. Due to the fact that the overhead crane with upper truss girders can transport a container above the upper layer of the stack, a spare half-layer is also created, which is very important in order to be able to make optimum use of the stack area.

[0025] By constructing the frames of the overhead cranes from two truss girders having a height which is slightly greater than the height of a container, it is possible to produce a light-weight structure, which still has a greater strength and rigidity than traditional overhead cranes. The dead weight of the overhead cranes is thus much lower than that of the current overhead cranes, and significantly lower than the dead weight of the RMGs. [0026] Each overhead crane comprises means for picking up and hoisting the containers. This may be a spreader which is known per se. Even if the crane only comprises one spreader, the crane can still lift two containers simultaneously. This is achieved by the fact that the frame is provided with a number of rotatable or tiltable supports near the underside of a floor part which is displaceable in the longitudinal direction. A first container can be held in the frame by means of such supports, while the spreader can move to an adjacent position in order to pick up a second container. I n this example, it would thus be possible to transport four 40-foot or eight 20-foot containers simultaneously in the longitudinal direction of the stack area, as a result of which the problem of congestion is effectively solved.

[0027] At a location in the stack area which is to be freely determined, a higher crane track may be fitted transversely across the lanes of the assembly of the overhead cranes, thus making it possible to move the overhead cranes from one lane to another lane in a simple manner. This may be useful in case of defects and breakdowns, but also, for example, if additional capacity is required in a certain area of the stack.

[0028] I n contrast with conventional RMGs, this system makes it possible to move the containers in a direction parallel to the quayside instead of in a direction at right angles to the quayside.

[0029] It will be clear that the current RMGs could also be fitted with a truss frame according to the invention (see Figs. 12 and 13), so that they can transport more than one container at the same time. Although this would increase the operating speed, it would not eliminate the abovementioned drawbacks of greater dead weight, inability to pass each other and the high centre of gravity.

[0030] Moreover, the current RMGs are virtually always used in stack lanes in which the longitudinal axis of the containers is situated at right angles to the quayside.

[0031] The invention further provides a vehicle, such as a Automated Guided Vehicle (AGV) for transporting containers, wherein the vehicle comprises a first set of wheels oriented along a first direction and a second set of wheels oriented along a second direction. The vehicle can be selectively supported by the first set of wheels or the second set of wheels. One set of wheels may comprise cog wheels. The cog wheels can engage with bars in a platform on which the AGV moves.

[0032] I n an embodiment, the first direction is perpendicular to the second direction. I n an embodiment, the first direction is in a longitudinal direction, that is parallel to the longest direction of the vehicle, and the second direction is in a transversal direction. When the vehicle is supported by one set of wheels (e.g. the longitudinal wheels) the vehicle can move in the longitudinal direction. When the vehicle is supported by the other set of wheels (e.g. the transversal wheels), the vehicle can move in the transversal direction. Effectively, the vehicle is a two-directional vehicle.

[0033] This advantageously allows for an "on the spot" turn over 90 degrees, which is not possible with known AGVs which require a relatively large turning arc. The wheels inside a set of wheels are not steerable with respect to each other. This simplifies the design a lot, compared to known AGVs where front wheels must be steerable with respect to rear wheels, and also allows to use many wheels (for example 6 wheels to each side of the vehicle, 12 wheels in total), thus distributing the weight over the many wheels. This in turn has the advantage that the load on each individual wheel is reduced. Such wheels can thus be easier and less expensively made. It also allows the overall weight of the vehicle to be reduced by using light-weight composites or plastics rather than the metal typically used in known AGVs.

[0034] The invention also provides an assembly of a vehicle as described above and a platform supporting the vehicle, said platform comprising guides adapted to cooperate with the wheels of the vehicle. In an embodiment, the platform comprises longitudinal guides and transversal guides configured to guide respectively longitudinal wheels and transversal wheels of the vehicle. I n particular where the vehicle is intended to be used in a predetermined area, it can be advantageous to confine the vehicle in the predetermined area using guides. Multiple vehicles can make use of the same area. Because each vehicle is limited by the guides, the chance of collisions is much reduced. The operator or vehicle guidance system only has to make sure that no two vehicles are active on the same guide portion. As long as the vehicles are on different guides, they cannot collide. Known AGVs tend to move around on flat surfaces without guides, making it much more likely that they accidently collide.

[0035] I n an embodiment according the invention, the vehicle is adapted to be stackable. Known AGVs are typically too heavy and cumbersome to be stacked under their own power or using a standard crane. The use of light-weight material makes it easier to stack the vehicle. By providing a vehicle with a upper carriage and an undercarriage, both carriages can be matched so that the vehicles can be efficiently stacked. I n an embodiment, the vehicle is configured to not only transport standardized containers, but also to transport other vehicles according the invention.

[0036] The invention also provides a storage rack that is designed to cooperate with a vehicle according the invention. The storage rack has an opening for receiving a vehicle carrying a container. The vehicle can then raise the upper carriage together with the container on top of it and deposit it on the supports of the storage rack. In this manner, an automated vehicle can automatically unload or load a container without the need for a (human operated) driven crane.

[0037] The invention also provides a platform comprising a roller conveyor and a vehicle suitable for movement on such a platform. The roller conveyor is adapted to cooperate with a vehicle having one (second) set of wheels comprising cog wheels which fit with the roller conveyor, in particular a toothed rack included in the roller conveyor, for movement in a transversal (second) direction. The other (first) set of wheels of the vehicle is adapted to move along longitudinal support elements, such as longitudinal pipes, to enable movement in the longitudinal (first) direction. Advantageously, the platform is configured so that the cog wheels are not obstructed by the longitudinal support elements when the vehicle moves in the longitudinal direction. The roller conveyor can be configured so that the first set of cylindrical wheel rolls are being supported by the roller conveyor when the vehicle is moving in the transversal direction. The roller conveyor can comprise rotable supporting elements, so that the cylindrical wheels can move over the rotating elements.

[0038] The invention also provides an assembly of a platform for AGVs according the invention, as described above, and an overhead crane according the invention, as also described above. The overhead crane is adapted to receive loads from an AGVs that is, during operation, located on (a part of) the platform. The platform, or at least another part of the platform, may also be accessible by a gripper from a Ship- To-Shore (STS) crane. The assembly according the invention can be used as follows. An STS crane places a container from a ship on an AGV on the platform. The AGV moves towards a designated area on the platform for delivering the container to an overhead crane. The overhead crane, using its gripper, picks up the load from the AGV. The reverse process is of course also possible, with an overhead crane delivering a container to an AGV, which then moves to another part of the platform offer the load to the gripper of the STS crane.

[0039] I n this assembly, the use of light-weight AGVs makes the use of a platform (preferably provided at a height above the ground) feasible. The lower weight of the AGV reduces the cost. The fact that the AGVs can make 90 degree turns on the spot reduces the needed area of the platform, and allows a more efficient use of multiple AGVs on the same platform. The overhead cranes according the invention provide the increased handling speed which combines with the increased handling speed of the AGVs, so that the overall system is made more efficient. Brief description of the Figures

[0040] The abovementioned aspects, features and advantages of the invention are explained in more detail on the basis of the figures, in which identical or similar parts are denoted by the same reference numerals. On the attached drawing sheets,

figures 1 and 2 show the use of conventional RMGs;

figures 3 and 4 show an assembly of two overhead cranes according to an embodiment of the inventions;

figure 5 shows an application of rotatable supports according to an embodiment of the invention;

figures 6, 7, 8, and 9 illustrate advantages of embodiments of the invention; figure 10 shows a cross section of an upper overhead crane according to an embodiment of the invention;

figure 1 1 shows a diagrammatic cross section of a container warehouse according to an embodiment of the invention;

figures 12 shows a rotatable spreader according an embodiment of the invention;

figure 13 illustrates an RMG fitted with a truss frame according to an embodiment of the invention;

figure 14 schematically shows a side view of a vehicle according the invention;

figures 15 and 16 schematically show a perspective view of a vehicle according the invention;

figure 17 schematically shows a front view of a vehicle according the invention;

figures 18 and 19 show details of an undercarriage of a vehicle according the invention;

figure 20 shows an assembly according to an embodiment of the invention of a vehicle and a platform;

figure 21 schematically shows an undercarriage and upper carriage according an embodiment of the invention;

figures 22 and 23 schematically show an exemplary arrangement for an undercarriage 2 according an embodiment of the invention;

figure 24 schematically shows an undercarriage variant with a mechanical system for raising and lowering; • figure 25 schematically shows an undercarriage variant with hydraulic cylinders for raising and lowering;

• figure 26 illustrates a stack of vehicles according to an embodiment of the invention;

· figure 27 schematically shows a perspective view of a vehicle according to an embodiment of the invention;

• figures 28, 29, 30, 31 , and 32 schematically show a vehicle according to an embodiment of the invention at various stages of the process of unloading a container onto a storage rack;

· figure 33 shows the possibility of raising one end of the AGV to enable exchanging a defect under carriage;

• figure 34 schematically show loading or unloading a container onto a storage rack in transversal direction.

• figures 35, 36, 37, 38 and 39 schematically illustrate a "roller principle"; and · figure 40 shows an assembly of an STS crane, an overhead crane, and

AGVs according to an embodiment of the invention.

Detailed description [0041] Fig. 1 shows the use of two conventional RMGs 1 for hoisting and moving containers 2, which run on rail tracks 1 1 , 12, one behind the other. The RMGs comprise a gantry structure 13 and a mechanism 14 for picking up and hoisting the containers 2, which is situated on an upper beam 15 of the gantry structure 13 and is displaceable with respect to said upper beam 15.

[0042] Fig. 2 shows the use of two conventional RMGs 1 a, 1 b for hoisting and moving containers 2, in which one of the RMGs is an oversized RMG 1 b which runs on a separate, extra wide rail track 12'.

[0043] Figs. 3 and 4 show an assembly 20 of two overhead cranes 21 , 22 according to the invention, which run one above the other in different horizontal planes, at a relatively short distance from each other, on rail tracks 23, 24 which are situated above ground level and which are supported by common columns 25. A lower overhead crane 21 comprises a truss frame 31 which is situated substantially below the level of the associated rail track 23, while an upper overhead crane 22 comprises a truss frame 32 which is situated substantially above the level of the associated rail track 24. [0044] It will be clear to those skilled in the art that variants of the overhead cranes 21 and 22 are possible in which the carriage 14 and hoist are arranged on top of the truss frame, as is illustrated in Fig. 3a.

[0045] Fig. 5 shows an application of rotatable supports 33 in the truss frame 32 of the upper overhead crane 22 which can be used to hold a container 2 inside the frame 32. The aspects which can be seen in Fig. 5 apply analogously to the lower overhead crane 21 .

[0046] The supports 33 may be configured in several ways. In Fig. 3, they have been shown as individual tiltable transverse supports. I n Figs. 4 and 5, these are coupled to each other, so that the bottom of the container is also supported in the longitudinal direction. An equivalent support (not shown) is also, for example, a floor structure which is displaceable in the longitudinal direction between the lower edges and has a length which may correspond to the length of a container.

[0047] Fig. 6 shows the advantageous fact that, with the assembly 20 according to the invention, it is possible for the frame 32 of the upper overhead crane 22 to be hoisted up by lower overhead crane 21 , after which said frame 32 can be transported to a replacement location or a workshop or another desired location. To this end, the frame 31 of the lower overhead crane 21 may be provided with lifting means.

[0048] Fig. 7 shows the advantageous fact that, with the assembly 20 according to the invention, it is possible for the frame 31 of the lower overhead crane 21 to be hoisted up by the upper overhead crane 22, if desired by means of the spreader, after which said frame 31 can be transported to a replacement location or a workshop or another desired location.

[0049] Fig. 8 shows the advantageous option where a truss frame 32 which is situated above the level of the associated rail track 24 is provided on one or two sides with an overhand 34 which extends beyond the rail track 24 and as a result of which it is also possible to set down or pick up a container in an adjacent stack lane.

[0050] Fig. 9 shows the advantageous option where an elevated transverse crane track 26 is provided in order to be able to transfer overhead cranes 21 , 22 from one lane to the other lane in the stack area. The transverse crane track 26 comprises supports which are placed on the horizontal carriers or crane track beams in which or on which the rails 23, 24 are arranged. The supports of the transverse crane track 26 are obviously placed on the horizontal carrier in such a manner that the overhead cranes 21 , 22 are displaceable beyond the supports. [0051] Fig. 10 shows a cross section of the upper overhead crane 22 with a hoisted container 2. I n order to prevent the container 2 from swinging sideways during transportation, horizontal supports 38 are actuated on both sides in at least two positions per container 2. In this example, the supports 38 comprise vertically oriented spring steel strips with a slight initial deflection which are pushed up to a side wall of the container 2 by a pressure mechanism 35. When the upper overhead crane 22 has reached its destination, the pressure mechanism 35 will then rise, if desired automatically, and the container 2 can be set down.

[0052] It is also clearly shown in Fig. 10 that, due to the relatively large width of the truss frame 32 of this new type of overhead container crane 22, it is possible to design the carriage 36 and the hoist 37 in such a manner that the construction height is minimal, thus saving space in the overall configuration of the assembly 20 of two overhead cranes 21 , 22. The aspects which can be seen in Fig. 10 apply analogously to the lower overhead crane 21 . It will be clear to those skilled in the art that variants of overhead cranes 21 and 22 are possible in which the carriage and the hoist are fitted on top of the truss frame.

[0053] As is the case for overhead carriage and the hoist, the shape of the truss frame also offers the possibility of using a rotatable spreader. Figs. 12 and 13 show how a rotatable spreader 14 can position and fix itself between the bottom members of both truss girders. Although Fig. 13 relates to an RMG on a rail track 1 1 , 12 at ground level, it will be clear to those skilled in the art that spreader 14 which is rotatable in the horizontal plane can be used in any (truss) frame according to the invention.

[0054] Above, an overhead crane 21 , 22 for hoisting and moving containers 2 has been described which comprises a rail track 23, 24 which rests on the ground by means of columns 25, and a frame 31 , 32 which is displaceable along the rail track 23, 24 and is provided with means for picking up and hoisting containers 2. The frame 31 , 32 is provided, for example, on two sides with wheels which run on the rails of the rail track 23, 24. I n particular, the frame 31 , 32 is a truss frame which is suitable for accommodating at least one container 2 completely. I n an assembly 20 of at least two overhead cranes 21 , 22 as described, the rail tracks 23, 24 of the overhead cranes 21 , 22 extend at different levels with respect to the ground, substantially parallel with respect to each other, and rest on the ground by means of common columns 25. This arrangement has the significant advantage that the overhead cranes 21 , 22 can pass one another in the case of a failure and that each can pick the other up and transport it to a replacement location. [0055] Although the above description of the overhead cranes is mainly directed at their use in container terminals, a number of advantages also apply to their use in warehouses and distribution centres, as is illustrated in Fig. 1 1 .

[0056] Fig. 1 1 is a diagrammatic cross section of a container warehouse 40. When using a conventional overhead crane 39, the crane track beam has to be fitted in a higher position than when an overhead crane according to the invention with an upper truss beam is used.

[0057] This means that the horizontal braking forces act at a higher point above ground level, which will require the building to be made stronger in order to achieve the same rigidity than is the case with a crane rail beam which is situated at a lower level.

[0058] Another drawback of the conventional overhead crane is the fact that, due to the safety requirements related to resolving failures and maintenance, a larger space has to be allowed between the crane 39 and the roof structure 40, which means a taller building than when an overhead crane according to the invention is used.

[0059] The advantage of a lower dead weight of crane 22 compared to crane 39 has already been described above.

[0060] Figure 13 schematically shows a side view of a two-directional vehicle 100 according the invention. The vehicle comprises an upper carriage 101 , suitable for supporting a container, such as a standardized container for sea or land transport, and one or more undercarriages 102. The upper carriage is provided with pockets 1 15 (see figure 20) to receive twist locks of standard 20', 40' and 45' containers.

[0061] I n figure 13, three undercarriages 102 are shown. Each undercarriage 102 is provided with an electrical engine 108 arranged to propel the vehicle and comprises two rows of wheels 103, one row on either longitudinal side of the undercarriage, oriented to move in a longitudinal direction and two rows of wheels 104 oriented to move in a transversal direction perpendicular to the longitudinal direction. In the example shown in figure 16, both sets of wheel rows 16, 17 comprise 103 wheels per row.

[0062] The vehicle according to an embodiment of the invention is made of lightweight materials, such as fiber reinforced plastics. I n particular in the upper carriage 101 and in the wheels the weight can be reduced as compared to known AGV designs. This is due to the fact that the steering arrangements of known AGVs are not needed in vehicles according to the invention combined with the fact that the weight may be divided over more wheels per container than in known AGVs. The use of light-weight materials results in lower manufacturing costs for the vehicle. In addition, the structural requirements for the supports of any structure on which the vehicle according the invention will be placed are advantageously reduced. For example, an AGV according the invention can more easily be used on a raised platform 130 that is supported by columns than traditional, heavier, AGVs.

[0063] The undercarriages 102 are interchangeable. When there is a defect with one of the undercarriages 102 of a vehicle, the broken undercarriage can be removed from the upper carriage 101 and replaced by another undercarriage (as schematically shown in figure 33). In an embodiment according the invention schematically illustrated in figure 21 , the upper carriage has holes 1 10 which can receive pins 109 provided on an undercarriage 102. After the pin 109 is placed in the hole 1 10, the connection may be locked (not shown) to prevent accidental disconnection or relative movements of the upper and undercarriages.

[0064] Since the longitudinal and transversal sets of wheels are oriented in two different directions, the vehicle can move in said two different directions, depending on which set of wheels currently support the vehicle. I n the shown example, the two sets of wheels 103, 104 are oriented perpendicular to each other. Such a vehicle is suited for transporting containers over a structure comprising a horizontal plane provided with rails or general guiding profiles, wherein the rails or profiles are adapted to guide the wheels of the vehicle. Two sets of rails or profiles may be supported, each set being perpendicular to the other. When the vehicle is correctly placed on such a structure, one set of rails can engage with the longitudinal wheel set 3, and the other set can engage with the transversal wheel set 104.

[0065] However, vehicles according the invention are not limited to support structures provided with guiding rails or profiles. For example, vehicles can also be configured to move on concrete or general hardened terrain with or without gutters or rails or any other guiding structure. A vehicle may for example be provided with computer vision capability and/or laser guiding means so that a guiding structure in the support is not needed.

[0066] Figures 18 and 19 show details of an undercarriage of a vehicle according to an embodiment of the invention. The vehicles can be provided with means for lowering and raising the transversal wheels 104. The means for lowering and raising are powered by electrical or pneumatic or hydraulic systems 131 . The means to propel the wheels 103 and 104 can be electro motors 108. Figure 18 shows the wheels 104 in raised position and figure 19 shows the wheels in lowered position. With the wheels 104 in a raised position, only the longitudinal wheels 103 make contact with the supporting structure and thus determine the direction in which the vehicle can move. With the transversal wheels 104 in the lowered position, the longitudinal wheels 103 no longer make contact and the transversal wheels 104 support the vehicle. Now the vehicle is configured to move in a transversal direction.

[0067] I n an alternative embodiment according the invention, the vehicle itself is not provided with means for lowering and raising the transversal wheels 104 moving in transversal direction. I n this embodiment, the selective support of the first or second set of wheels must be achieved by special provisions built in the platform 130' supporting the vehicle. Figures 35, 36, 37, 38 and 39 schematically illustrate, as an example, a "roller principle" using roller conveyor 210 in platform 130'. Other principles are also possible.

[0068] When the "roller principle" is used, the under carriage has two or more cylindrical wheel rolls 21 1 instead of wheels 103 to move in longitudinal direction and has two or more cog wheels 212 to move in transversal direction. A lowering or raising system is in this embodiment not necessary.

[0069] The electromotor 213 propels the cog wheels 212 which turn in a horizontal toothed rack 215 and move thus the AGV over the roller conveyor 210. In the example of figures 37 and 38, the toothed rack 215 is actually formed of short cylindrical elements that are dimensioned and spaced so that they can engage with the cog wheels 212. The term "toothed rack" in this context can thus indicate any structure that is suitable for engaging with the cog wheels 212 of the vehicle. The surface of the solid platform 130' comprises, in this example, a number of steel pipes 214, oriented along a longitudinal direction, with intermediate spacing so that the cog wheels 212 are adapted to the surface formed by the steel pipes 214 and longitudinal movement along pipes 214 is possible without the cog wheels 212 causing an obstruction (see figure 38).

[0070] The roller conveyor 210 also comprises shorter steel pipes with the same orientation and diameter as the longitudinal pipes 214, but without spacing in between. The shorter steel pipes have on both sides the fixed horizontal toothed rack 215, the rack 215 being oriented in a transversal direction. When the cog wheels interact with the toothed rack 215, and the vehicle can move in a transversal direction, the cylindrical wheel rolls 21 1 rest on the shorter steel pipes of the roller conveyer 210, so that the vehicle can move in transversal direction. The shorter steel pipes are rotatable, so that the cylindrical wheels can move in a transversal direction without significant friction from the roller conveyor 1 10. [0071] It is to be understood that instead of the electro mechanical system as described before the movement of the AGV over the roller conveyor can be realized by various different systems for example electromagnetic.

[0072] Regardless of whether the vehicle or the platform is provided with means for selectively using one set of wheels or the other, the vehicle is limited to two directions of movement. An advantage is that the undercarriage is less complex than in known AGVs, since there are no steerable wheels, and the vehicle is configured to make a 90 degree turn "on the spot" that is, without requiring additional movement space as is the case with known AGVs.

[0073] The raising/lowering mechanism shown in figures 18 and 19 can be implemented in different ways. For example, it is possible to configure the transversal set of wheel 103 for raising and lowering instead of the transversal set of wheels 104. Also, the number of wheels per row, the number of rows per set, and the number of undercarriages can be modified.

[0074] There are various ways in which a skilled person may implement the raising and lowering mechanism, including a system using a hydraulic piston, a pneumatic piston, or a mechanical construction comprising gears and worm gears.

[0075] Figure 20 shows an assembly according to an embodiment of the invention of a vehicle and a platform 130, the platform 130 comprising a grid of rails or other types of guiding elements 106, which may form guides for longitudinal or transversal rows of wheels 103, 104. At predetermined intervals, guides or rails 103' are provided for longitudinal wheels 103 and, perpendicular thereto, guides or rails 104' for transversal wheels 104.

[0076] The platform 130 of figure 20 may be placed at a height, supported by e.g. columns (not shown in figure 20). The space between the guides 103', 104' may be filled with e.g. covering panels or may be left open.

[0077] The platform 130 of figure 20 may be provided with a rail for providing electrical power 107. This electrical rail 107 can for example be provided adjacent to each longitudinal rail 103', with an electrical contact provided on the vehicle adjacent one row of longitudinal wheels. The vehicle electrical contact can be arranged to make an electrical connection with the rail regardless of whether transversal wheel set 104 is raised or lowered. I n addition, a transversal set of electrical rails (not shown in figure 20) may be provided along the transversal guides 104'. Other arrangements for providing current to a vehicle from a grid are also available to a skilled person. Use of an electrical rail 107 removes the need for a (large) battery in electrically driven vehicles according the invention. [0078] It is also possible to provide a hybrid rail-powered / battery-powered system. For example, the vehicle may be arranged to draw current from an electrical rail 107 while driving in a longitudinal direction, so that rail 107 powers the longitudinal wheels 103 on guides 103'. For transversal movements along guides 104' it may use a battery to power wheels 104. This advantageously requires only longitudinal electric rails 107, while for the (sometimes relatively short) distances travelled in transversal directions a battery is used. The battery may advantageously be charged by drawing current from the electric rail 107 while the vehicle is supported by the longitudinal wheels 103. Of course, the arrangement may also be reversed, with the longitudinal wheels battery powered and the transversal wheels powered by a rail. Any battery may also be (additionally) charged by the breaking power of the vehicle.

[0079] Figures 22 and 23 schematically show an exemplary arrangement for an undercarriage 102 according an embodiment of the invention. A row of wheels 103 is provided on a bar 121 , which bar 121 is movably connected to the frame 120 of the undercarriage 102. The bar 121 and frame 120 are connected by rods 122 and the movement is executed by tension or compression elements 1 12. The elements 1 12 can for example be pneumatic, hydraulic, or mechanical.

[0080] I n figure 22, the undercarriage 102 is ready to receive a load (such as a container placed on top of the upper carriage 101 , not shown in figure 22 and 23). Figure 23 shows the situation with the additional weight (F) of an container on top of the undercarriage. The additional weight results in more compressed dampening elements 1 12.

[0081] Figure 24 shows a variant with a mechanical system for lowering or raising the upper carriage. Electromotor 108' drives a shaft with worm gears, which worm gears interact with cogs to turn levers 1 12, thus raising or lowering the bar to which wheels 103 are connected. Figure 25 shows a variant with a system using hydraulic cylinders 132 for lowering or raising the upper carriage.

[0082] Figure 26 illustrates a stack of AGVs according to an embodiment of the invention. The undercarriage 102 frame has the same (transversal) width as the width between rows of longitudinal wheels 103. This advantageously allows the AGVs to be stacked. This ability to stack AGVs advantageously allows quick replacement of AGVs. A malfunctioning AGV can be loaded on top of a functioning AGV and moved away by the functioning AGV. I n addition, a stack of AGVs requires no more ground area than a single AGV, and thus the supply of spare AGVs in a container terminal takes up less space than with known AGVs which are not stackable. The container guides 1 13 (see below) can be used, in raised position, to stabilize a stack of AGVs.

[0083] Figure 27 schematically shows a perspective view of a vehicle according to an embodiment of the invention. The vehicle is provided with container guides 1 13 that can hold or at least limit the horizontal movement of a container on the AGVs. The container guides 1 13 prevent the container from falling off the AGV. I n figure 27, the container guides 1 13 are shown in raised position. The upper carriage 102 comprises space 1 14, between undercarriages 101 , which can hold for example (control) electronics and/or batteries.

[0084] According to an embodiment of the invention, the vehicle can be automatically loaded and unloaded using a specifically designed storage rack 140. Figures 28, 29, 30, and 31 schematically show a vehicle according to an embodiment of the invention at various stages of the process of unloading a container 150 onto a storage rack 140 comprising longitudinal supports 141 arranged to support a container. The upper carriage 101 is provided with a supporting grid 1 16, shown in figure 1 19, comprising two or more longitudinal ribs. Figure 1 19 shows three ribs 1 16. The ribs are removably attached to the upper carraige 101 , and are thus raised and lowered together with the upper carriage. The ribs mainly serve to separate the container 150 on the vehicle from the upper carriage 101 . The ribs can also be considered a part of the upper carriage, in which case the upper carriage 101 directly supports the container 150.

[0085] The system for raising and lowering the upper carriage 101 as described for example in reference to figures 24 and 25 can therefore serve two purposes, namely the raising of the upper carriage so that the vehicle is supported by longitudinal wheels 103, and raising the container on the ribs 1 16.

[0086] The undercarriage in the example of figures 14, 15, 16, 17, 20, 21 , 26, 27 and 28 - 32 is provided with vertical container guides 1 13 that will be raised in case the AVG receives a container out of a crane. Before the AGV moves into the storage rack 140 the upper carriage with container will be raised to get the bottom of the container above the level of storage rack 140 supports 141 . When the vehicle carrying a container is moved into the storage rack 140 (figure 26) the container guides 1 13 are lowered to avoid contact between the supports 141 and the rack 140.

[0087] I n figure 29, the vehicle is partly between the supports 141 of the storage rack 140, and moving further into the storage rack 140. Once the vehicle carrying the container is fully positioned between the supports 141 , it can be lowered so that the container will be transferred from the vehicle to the storage rack on top of the supports 141 .

[0088] I n figure 1 17, the container is fully supported by the storage rack, and the unloaded vehicle can move away. The container guides 1 13, once they are clear of the storage rack 140, are raised again so that a new container may be received by the vehicle.

[0089] I n the examples of figure 28 - 32, a storage rack 140 is disclosed that is arranged for a vehicle to move through in a longitudinal direction (that is, parallel to the longest dimension of a container). However, since the vehicles according the invention can move also in a transversal direction, a storage rack 160 with transversal supports 161 , which rack is arranged for a container-carrying vehicle moving in a transversal direction (that is, parallel to the shortest horizontal dimension of a container) is also possible according to an embodiment of the inventions (see figure 34). In this case, the vehicle is provided with a transversal support grid 1 16', which is, also adapted to raise or lower the container 150 by being fixed to a raisable and lowerable upper carriage 101 or through raising/lowering means independent of the upper carriage 101 .

[0090] The principle of loading and unloading an AGV with a storage rack 140 or 160 may also be summarized in that the vehicle has a raisable and lowerable container-supporting structure with which the container can be raised so that the container may be positioned on a supporting element 141 or 161 of the storage rack 140 or 160.

[0091] Figure 40 shows an assembly of an STS crane 300, an overhead crane assembly 20 on supports 25, and AGVs 100, according to an embodiment of the invention. The exemplary STS crane 300 has a superstructure that is movable parallel to the quay on wheels supported by rails 301 . I n this example, two sets of rails 301 are provided, supported at different heights above the quay floor. However, the invention can also be used in more conventional STS crane designs, for example using rails in the quay floor. The STS crane 300 has a gripper 302 for picking up containers 2 from container ship 400, or for placing containers 2 on the ship. The gripper 302 can reach the left side (water side) of platform 130, so it can deposit containers 2 on 2D AGV 100 or retrieve a container from a 2D AGV. The overhead crane assembly 20 has one or more overhead cranes 21 (not shown), 22. The overhead cranes can reach the right side (land side) of the platform 130, and may thus pick up a container from a 2D AGV or put a container on the AGV. The cranes can then deposit the containers 2 in various stack areas that are accessible from the overhead crane assembly. The overhead cranes may be provided with a rotatable gripper 14, so that the orientation of the containers as stored in the stack area need not be the same as the orientation on the 2D AGV or indeed as stored on the ship 400. The 2D AGVs can move over the entire platform 130, so they are configured to bring containers from the water side to the land side and vice versa. The limitation to 2D movements advantageously reduces the manoeuvring space needed by the AGVs compared to conventional AGVs, in particular conventional AGVs on the quay surface.

[0092] It will be clear to the skilled person that figure 40 is but an exemplary assembly of various aspects of the invention, and that in fact any combination of STS cranes, overhead cranes, and AGVs as disclosed in this application is possible. For example, conventional STS cranes may be used, the AGVs may move on the quay floor rather than on a platform, the overhead cranes may be (partially) conventional cranes as e.g. in figure 13, the AGVs can be conventional AGVs (i.e. able to move in all directions) or 2D AGVs using a different direction-changing mechanism than disclosed here, etc.

[0093] Various aspects of the invention as described in this application have been tested through computer simulations.

[0094] Simulation results for the overhead cranes (2 cranes per lane) according the invention showed an increased stack density of about 1400 TEU/Ha, compared to 1 100 TEU/Ha for conventional RMGs. According the simulations, the overhead cranes performed 60 moves/hour, compared to just 20 for the RMGs. The weight of the overhead cranes needs to be just 20 Tons, instead of 120 Tons for a conventional RMG system. The simulations show a reduction of travel distance per move, and a reduction of travel time per move. As a result, the terminal area can be decreased. A higher stack density results in a higher store capacity. Overall, flexibility is increased and operational and investment costs are reduced.

[0095] The use of 2D AGVs showed a substantial reduction in AGV travel distance and a substantial increase in crane productivity. According to the simulations, 6 conventional AGVs were able to handle 30-40 containers/hour, resulting in a crane productivity of 47% and an average travel distance of about 600 meters. I n contrast, just 3 2D AGVs according the invention were able to handle 48-76 containers per hour, resulting in a crane productivity of 88% and an average travel distance of about 220 meters. The AGVs according the invention thus allow a reduced terminal area. The rotatable gripper makes it easier to allow truck loading parallel to the quay. This removes the need for backing trucks and increases safety. [0096] I n the foregoing description of the figures, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the scope of the invention as summarized in the attached claims.

[0097] I n particular, combinations of specific features of various aspects of the invention may be made. An aspect of the invention may be further advantageously enhanced by adding a feature that was described in relation to another aspect of the invention.

[0098] It is to be understood that the invention is limited by the annexed claims and its technical equivalents only. I n this document and in its claims, the verb "to comprise" and its conjugations are used in their non-limiting sense to mean that items following the word are included, without excluding items not specifically mentioned. In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

[0099] Aspects of the invention are summarized in the following clauses:

1 . Overhead crane (21 , 22) for hoisting and moving containers (2), comprising a rail track (23, 24) which rests on the ground by means of columns (25), and a frame (31 , 32) which is displaceable along the rail track (23, 24) and is provided with means for picking up and hoisting containers (2), wherein the frame (31 , 32) is movable along the rail track (23, 24), and wherein the frame (31 , 32) is suitable for accommodating at least one container (2) completely.

2. Overhead crane (21 , 22) according to Clause 1 , wherein the frame is a truss frame (31 , 32).

3. Overhead crane (21 ) according to Clause 1 or 2, wherein the frame (31 ) is situated substantially below the level of the rail track (23).

4. Overhead crane (22) according to Clause 1 or 2, wherein the frame (32) is situated substantially above the level of the rail track (24).

5. Overhead crane (22) according to Clause 4, wherein, on at least one side of the frame (24), an overhang (34) is provided which extends beyond the rail track (24).

6. Overhead crane (21 , 22) according to any of Clauses 1 -5, comprising at least a rotatable or tiltable support (33) or a floor part which is displaceable in the longitudinal direction which is arranged near an underside of the frame (31 , 32) in order to support a container (2) after this has been hoisted and positioned inside the frame (31 , 32) by the crane (21 , 22).

7. Overhead crane (21 , 22) according to any of Clauses 1 -6, comprising supports (38) and a pressure mechanism (35) for pressing the supports (38) against a side wall of a container (2) which has been hoisted and positioned inside the frame.

8. Overhead crane (21 , 22) according to any of Clauses 1 -7, wherein the means for picking up and hoisting containers (2) comprise a spreader (14), which spreader is rotatable in a horizontal plane.

9. Assembly (20) of at least two overhead cranes (21 , 22) according to any of Clauses 1 -8, wherein the rail tracks (23, 24) of the overhead cranes (21 , 22) extend substantially parallel to each other at different levels with respect to the ground, and rest on the ground by means of common columns (25).

10. Assembly (20) according to Clause 9, wherein an overhead crane (21) is situated substantially below the level of its rail track (23) and another overhead crane (22) is situated substantially above the level of its rail track (24).

1 1 . Assembly (20) according to Clause 9 or 10, wherein an overhead crane (22) which is situated at a higher level is provided with a mechanism which is configured to hoist the frame (31) of an overhead crane (21) which is situated at a lower level. 12. Assembly (20) according to any of Clauses 9-1 1 , wherein an overhead crane (21) which is situated at a lower level is provided with a mechanism which is configured to hoist the frame (32) of an overhead crane (22) which is situated at a higher level.

13. Assembly (20) according to any of Clauses 9-12, furthermore comprising a rail track (26) which is situated at a higher level with respect to the ground than the substantially parallel rail tracks (23, 24) of the at least two overhead cranes (21 , 22), and extends substantially at right angles to said rail tracks (23, 24).

14. Assembly (20) according to Clause 13, wherein at least two parallel lanes are provided, wherein each lane is provided with at least one overhead crane (21 , 22) and the rail track (26) is configured to transport an overhead crane (21 , 22) from one lane to the other lane.

15. Container warehouse (40) provided with an overhead crane (21 , 22) according to any of Clauses 1 -7.

16. Frame, preferably a truss frame (31 , 32), having the features of the frame of one of Clauses 1 -7, configured to be fitted to the supporting structure of an overhead crane which is placed on rail tracks (1 1 , 12) at ground level.