Device for handling loads and steering system for same The present invention relates to a device for handling loads, comprising a carrier and a boom equipped with load gripping means, which boom is articulated with respect to the carrier, and where the carrier comprises a plurality of turnable ground contact means. The invention also relates to a steering system for a device for handling loads, which device comprises a plurality of ground contact means designed to be interconnected so as to turn in parallel with each other, a upper part and a lower part that are rotatable relative to each other, a first steering mechanism for turning the ground contact means and a second steering mechanism for rotating the upper part with respect to the lower part.

Such a device is known e. g. as a so-called reach stacker, and is for instance described in Swedish published patent application no. 9702788. However the reach stacker came on the market as early as in the 70s, and was universally accepted in the 80s. It can be described as a counterweight lifting truck, where the vertical lifting device has been removed and replaced by a telescopic boom that is attached to the rear of the vehicle and has the lifting device (spreader) at the front. This boom and the spreader that grips the top of the container are, in principle, the only things that have been carried over from the conventional reach stacker to the present invention.

In principle, the conventional reach stacker has the same type of wheels and steering as a conventional forklift truck, i. e. steering of one set of wheels, normally the rear wheels, within a limited angle. This entails that the reach stacker having a certain minimum turning radius, and thereby requiring a certain minimum of space in order to manoeuvre. Further, the reach stacker must reverse out of confined spaces where there is not enough room to turn around. Since only one set of wheels can turn, the vehicle, which when driving forwards turns the wheels that face away from the direction of driving, will when reversing turn those wheels that face the direction of driving. By so doing, the vehicle will behave differently when driving forwards and when reversing. If the container to be collected is situated behind the reach stacker, this has to be turned in order to gain access to the container, which may present a problem in the event of little room. As such, container areas must be planned carefully, and a considerable amount of space must be set aside just to manoeuvre the reach stacker.

Other container handling devices are also known, for example as shown in US 3 081 883, WO 9602454, WO 9602455 and US 4 880 124. However all of these container-handling devices are designed as gantry cranes, where the load is carried inside the portal. Unlike the reach stacker, the above mentioned gantry cranes are equipped with wheels that may turn unrestricted through an angle of 360°.

The disadvantages of gantry cranes are obvious. They require a lot of space next to the container to be transported. True, they may be used to stack containers when the conditions are right, and they must always have space to drive on both sides of the stack of containers.

They are unable to reach containers located at a distance from the crane without moving.

Sideloaders for containers are also known, where a davit-like lifting device is provided in order to lift a container onto a truck body. The vehicle is equipped with wheels on four axles, where all the wheels can be steered. However the turn of wheels is limited, and as such the vehicle has a certain turning radius that causes it to require a lot of room in order to turn. Furthermore, containers can only be handled on one side of the vehicle.

Other transport means with turnable wheels are also known, for transporting containers onto a truck body, so-called AGV (Automatic Guided Vehicle). This vehicle is not equipped with a boom, but is designed to collect containers from a ramp. The truck body may be raised and lowered in relation to the ramp.

The present invention aims to provide a load-handling device that will greatly reduce or eliminate the above described disadvantages of known devices. This is achieved by a device as mentioned in the introduction, characterised in that all the ground contact means are designed to be interconnected so as to turn in parallel with each other.

By designing the load-handling device in the above manner, it will never need to turn around the way reach stackers do. It has unbounded possibilities for immediate changes of direction, and may thereby drive out of a confined space the same way it drove into it. Thus the road between the stacks of containers can be reduced to approximately 60 % of today's width. This alone gives an increase in the utilisation of the available space, from 15 to 40% when compared with those reach stackers that stack containers in up to 3 and 4 rows.

In an advantageous embodiment, the carrier comprises an upper part to which the boom is fixed, and a lower part to which the ground contact means are coupled, where the upper part is rotatable about a vertical axis with respect to the lower part.

Preferably the lower part includes six sets of wheels, all of which are synchronised, e. g. mechanically or hydraulically, and oriented in the same direction. The wheels are mounted in pairs of two on a short axle, which in turn has a vertical pivot up halfway between the wheels. The sets of wheels are preferably rotatable through 360° about their vertical axes with respect to the lower part. This is the rotation that results in the vehicle changing direction.

In a further advantageous embodiment, the upper part and the lower part are assembled from modules comprising sector elements of such a size that they fit in an ISO container, singly or several in the same container.

A novel steering system according to the present invention is characterised in that a movement of the first steering mechanism in a chosen direction directs the ground contact means for driving in the chosen direction, that the direction of driving relative to the points of the compass is maintained during rotation of the upper part as long as the deflection of the first steering mechanism is maintained, and that a return of the first steering mechanism to the neutral position results in a new movement of the first steering mechanism directing the ground contact means in the same direction as the first movement of the steering mechanism, regardless of to what degree the upper part may have rotated relative to the lower part in the meantime.

The invention will now be explained in greater detail with reference to the accompanying drawings, in which: Figure 1 shows a first embodiment of a load-handling device according to the invention; Figure 2 shows a second embodiment of the present invention;

Figure 2b shows another embodiment of the present invention; Figures 3-6 show further embodiments of the present invention; Figure 7 shows a perspective view of a lower part of the load-handling device according to the present invention; Figure 8 shows the modular construction of a load-handling device according to the embodiment in figure 2; Figure 9 shows a perspective view of a sector of the lower part of the load-handling device according to figure 8; Figure 10 shows a perspective view of the wheel suspension for the load-handling device according to figure 8; Figure 11 illustrates the range of the load handling device according to the present invention; and Figure 12 illustrates the space required to manoeuvre the load-handling device according to the present invention, compared with a known load-handling device.

Figure 1 shows a first embodiment of the load-handling device according to the present invention, hereinafter called a container stacker. It generally comprises a boom 1, which at its distal end 2 is equipped with a container spreader 3. This container spreader 3 is of a conventional type, and different types of these are presently in use in portainers, container trucks and other container handling devices. The boom 2 is linked to a tower 5 by its proximal end 4. The tower 5 is arranged on a carrier 6. The carrier 6 is in turn divided into an upper part 7 and a lower part 8. The lower part 8 is equipped with wheels 9. Supports 11 have been provided between the wheels 9, which supports can be lowered when the container stacker is to carry out heavy or difficult lifting and requires increased stability. By so doing, the wheels can also be relieved during the lifting operation.

The wheels 9 can be rotated about vertical axes 10 in pairs (see figure 7). The boom 1 is telescopic. A counter weight 12 is integrated into the rear part of the tower 5 or the upper part 7. One or more lift actuators (not shown) are built into the tower 5 and may for instance be a motor (not shown) functionally coupled to the boom via a gear system (not shown).

On the upper part 7 is a generally flat area 115 on which can be placed a container for transport. This is shown in figures 8 and 12. Long containers will project outside of the upper part 7, and the upper part 7 may therefore be equipped with telescoping levers (not shown) that can be extended horizontally in the longitudinal direction of the container in order to support it at the container ends. With a container in this transport position, the boom 1 with the spreader 3 is freed up for handling other containers. During driving, the boom 1 can be fully retracted so as not to project outside the upper part 7 or only project slightly outside of it, and the container stacker will require a minimum of space. It can therefore manoeuvre in very confined spaces, as explained below in connection with figure 12. Thus the area 115 makes it possible to carry two containers along the transport distance, one on the area 115 and one in the spreader 3. Thereby the capacity of the equipment is almost double when compared with the reach stacker.

Figure 2 shows an alternative embodiment of the container stacker in figure 1. Here, the tower 5 is replaced by a portal 13, the two legs 13a and 13b of which are rotatably supported on either side of the boom 1 and extend to an articulation 14a and 14b on the upper part 7. The front lifting cylinders 15 and 16 and rear lifting cylinders 18 and 19 extend from the boom 1 to the upper part 7 and are designed to move the boom in the vertical plane in order to raise and lower the distal end 2. An operator's cabin 130 is located at the top of the boom 1. A cage 131 encloses the operator's cabin 130 in order to protect it.

From this location, the operator has a clear view of the entire field of activity, including all the way down to the lower part of a container e. g. on a railway carriage that has been placed behind another railway carriage that is positioned on a track in front. When an operator is to go from the ground and up to the operator's cabin 130, the distal end of

the boom 1 has been lowered to the ground in advance. The operator climbs up on the container spreader 3 and into a crew's basket (not shown). A predefined computer programme may be started from this by operating a control mechanism (not shown), which programme starts up the motor, raises the boom 1 with the crew's basket and brings this up to the operator's cabin. From here, the operator can get into the operator's cabin via a walkway (not shown).

Figure 2b shows yet another embodiment of the present invention. Here, the boom 1 is divided into an inner boom element 120 and an outer jib 121. The inner boom element 120 is joined to the tower 5 through an articulation 122 and lifted by means of a cylinder 123. The jib 121 is guided into the inner boom element 120 in an articulation 124 and lifted relative to the boom element 120 by means of a cylinder 125.

By this embodiment, it is possible to take hold of a container 126 that is positioned lengthways along the boom 1 even if this is at the sixth level. By stacking the containers lengthways instead of transverse, the stacking density is increased.

Figure 3 shows a further embodiment of the present invention. This embodiment also has a tower 5 like the embodiment in figure 1, but unlike the embodiment in figure 1, it is provided with one (preferably two) lifting cylinder (s) 20 that extends from the foot of the tower 5 to the front part of the outermost telescopic pipe of the boom 1.

Figure 4 shows a further alternative embodiment in which the tower 5 is a trussed construction. The near end of the boom 1 is suspended from the tower in an articulation 21. The articulation 21 is supported in a vertically moveable manner in the tower.

Movement of the articulation 21 may be effected in several ways, among other things by use of a wire lift or, as shown, by use of a scissor-type lifting device consisting of levers 22 and 23 that are interlinked at 24, and where the lower end of the lever 22 is attached to the upper part 7 in a horizontally moveable manner. The distal end 2 of the boom 1 is moved in the vertical plane by means of a wire lift 25.

Figure 5 shows yet another embodiment of the present invention. Here, the tower is replaced by a lever 26, and the proximal end of the boom 1 is attached to the lever 26

through an articulation 27. The lever 26 is linked to the upper part 7 through an articulation 28. A cylinder 29 extends from the upper part 7 to an articulation 30 on the boom 1. The boom 1 may be swivelled in the vertical plane by means of this cylinder 29. A cylinder 33 is linked to the upper part 7 through an articulation 34 by its lower end, and to the lever 26 in an articulation 35. The lever 26 may be swivelled about the articulation 28 by means of this cylinder. With this type of construction, the boom 1 does not necessarily have to be telescopic in order to have sufficient range, although there is nothing to prevent this. Figure 6 shows a combination of the design in figure 5 and a telescoping boom 1. This gives a considerable increase in range.

Figure 7 shows a preferred embodiment of the carrier 6. The upper part 7 has been removed so as to show only the lower part 8. The lower part 8 consists of three sector elements 8a, 8b and 8c. The sector elements each extend across a sector of a circle of 120°. The sector elements 8a, 8b, 8c are made from plate material, and may be joined in any suitable manner, e. g. by use of bolts through adjoining sides.

Figure 9 shows one sector element 8a. This comprises an outer curved wall 41 (see figure 7) and an inner wall 42 that are interconnected via small, vertical wall portions 150 and 151. Via these, sector element 8a is connected to the adjacent sector elements.

A top wall 43 extends between walls 41 and 42. Openings 44 are formed in the top wall 43. Recesses 49 are formed by the lower edge of wall 41, directly under the openings 44. The openings 44 are designed to receive a respective rotation bearing 141 on a set 55 of wheels. The recesses 49 provide room for rotation of the sets 55 of wheels and access to these for the purpose of maintenance.

A sector of a grooved rim 113 is provided at the joint edge of the top wall 43 and the outer wall 41, which sector has an inwardly facing groove 113a.

Each sector element 8a, 8b, 8c is equipped with two sets 55 of wheels. The sets consist of two wheels 56 and 57. One set 55 of wheels is shown in figure 10. In order to make it easier to show the construction of the set of wheels, one wheel has been removed so as to show only wheel 57. The wheels are arranged rotatably on a wheel carrier 58. A pivot 53 is attached to the wheel carrier 58. The pivot 53 may be telescoped hydraulically and

takes up the weight of the container stacker. A rotation bearing 141 is provided at the upper end of the pivot, and also comprises a worm drive. The pivot is equipped with a flexible organ 142 (here in the shape of a curved spring). The organ 142 is designed to transfer rotation from the rotation bearing 141 to the wheel carrier 58, as the pivot itself is unable to transfer torque. A hydraulic motor 141 a is coupled to the worm drive, so as to let the pivot 53 be rotated about its longitudinal axis and thereby rotate the set 55 of wheels. An angle sensor 141b is also provided in connection with the rotation bearing 141.

In the wheel carrier 58, there are preferably two hydraulic motors (not shown) that are designed to drive the respective wheels 56 and 57. The motors are connected in parallel to allow them to drive the wheels synchronously in the same direction. The speed of each of the wheels in the set 55 of wheels may obviously differ slightly when the container stacker is in motion, as one wheel may be going through the outside of a curve with respect to the other wheel.

When the container stacker is to change direction from the stationary state, the motor that drives the rotation bearing 141 will rotate the set 55 of wheels about the pivot 53.

The wheel motors 56 and 57 then co-operate hydraulically in such a manner that the motors rotate in opposite directions, as a hydraulic differential gear. The set of wheels is therefore able to turn on a penny. Advantageously, a hydrostatically closed transmission system takes care of the operation of e. g. every other set of wheels.

Figure 1 Oa shows a schematic side view of an alternative embodiment of the set 55 of wheels. Here, the pivot 53 and the springs 142 are replaced by a swivel arm 140, one end of which is connected to the rotation bearing 141, and the other end of which is connected to the distal end of a damping arm 143. The damping arm is in turn rigidly fixed to the wheel carrier 58. A second end of the damping arm 143 is connected with a hydraulic cylinder 144. The cylinder extends between the damping arm 143 and the upper end of the swivel arm 140. The cylinder 144 or the telescopable pivot 53 ensures active hydraulic load distribution on the container stacker during driving, in such a way that all the sets of wheels are in contact with the ground at all times.

When lifting a heavy load, the set (s) of wheels closest to the load will be subjected to the greatest load. Correspondingly, the set (s) of wheels opposite of the load will experience the smallest load. In a static situation, the load on the sets of wheels will be linearly dependent on the distance from the load. Thus in an imaginary example of lifting of a load, the front set (s) of wheels (closest to the load) will be subjected to a load of approximately 100 tons, the middle set of wheels to approximately 60 tons, and the rear set (s) of wheels to approximately 20 tons. This is not a desirable situation, as it will require the sets of wheels to have very solid dimensions, based on the fact that it is not possible to know which will be the front set (s) of wheels in any given situation.

According to an embodiment of the invention, a hydraulic system has therefore been provided where those sets of wheels that are located between the front set (s) of wheels and the rear set (s) of wheel, and which will receive a medium load during lifting, will be forced somewhat harder against the ground than that which would be the case in a static, non-manipulated situation. These sets of wheels will thereby carry a greater share of the weight than in the above case. On rotation of the upper part with a suspended load, the system will ensure that the pressure is adjusted in such a manner that those sets of wheels that are between the front set (s) of wheels and the rear set (s) of wheels at any time will be forced against the ground with added contact pressure. In this way, the load on the front set (s) of wheels can be reduced to e. g. 90 tons, while the load on the middle sets of wheels is increased, e. g. to 80 tons. As a result of this, the sets of wheels may be dimensioned for lesser loads. In addition, the counterweight may for instance be increased by 10 tons in order to achieve sufficient stability.

The swivel motors for each set of wheels may be hydraulic or electric. Preferably, they are coupled hydraulically or electronically, in order to ensure synchronous movement.

When turning, the sets of wheels are able to turn in parallel corresponding to the change of direction in order to have the smallest possible turning radius (approximately 0), but it is also possible to imagine the container stacker turning with a greater turning radius if space allows, by turning the sets of wheels to a different degree. A solution without relative rotation between the upper part 7 and the lower part 8 may also be provided in this manner. This is however not preferred, as it will result in greater tyre wear and lesser accuracy during load handling.

As shown in figure 7, a large, open space is formed between the sector elements 8a, 8b, 8c. As shown in figure 8, this leaves room for a machinery room 40. The machinery room 40 holds e. g. a diesel engine 40 complete with cooling system, all hydraulic pumps, a swivel for leading oil through to the lower part 8, swivel gear and oil coolers etc.

An upper part 7 is arranged on top of the lower part 8. This is provided with castors 114 designed to engage a grooved rim 113 on the lower part 8, so that the upper part 7 may rotate with respect to the lower part 8. The upper part 7 has a counter weight 110, lugs 111 for cylinders 18,19 and lugs 112 for the portal 13 and cylinders 15,16. The upper part 7 is preferably divided into three elements; a front element 7a that provides the generally flat area 115 for placement of an extra container, a central element 7b that carries the portal 13 and a rear element 7c that carries the counterweight 110.

By the above described construction of the carrier 6, it can be divided into parts dimensioned so as to allow the container stacker to be transported in ISO containers.

As an alternative to the embodiment described above, where the rotation of the sets of wheels about the vertical axis is synchronised through use of a hydraulic or electrical system, the pivots of the sets of wheels may be interconnected via eccentric pins on a turntable mounted on the rotation bearing and rods extending between the eccentric pins, so that the rotational movement of one set of wheels is transferred to the adjacent set of wheels. By such an arrangement, it is only necessary for every other set of wheels to be equipped with a swivel motor, as the intermediate sets of wheels will be co-rotated by the rods.

If desired, the sets of wheels may be arranged in sets of two on a cradle suspended rockably from the sector element. By such an arrangement, the lower part 8 will in reality have a three-point support, and all wheels will be in contact with the ground at all times. However this requires that the seesaw motion of the cradles be lockable, for example hydraulically, in order to reduce tilting in the event of heavy loads.

Figure 11 illustrates the range of the container stacker, seen from the side. As can be seen, the distal end 2 of the boom reaches across four rows of containers placed outside each other. Up to four containers may be stacked on top of each other in the furthermost row 90, then five containers in the next row 91, and in the nearest two rows 92 and 93 it is possible to stack six containers on top of each other.

The container stacker is also able to reach containers 94 at a lower level than that of the support on which the container stacker is positioned, e. g. onboard a ship alongside a quay.

Figure 12 schematically illustrates, as an example, a comparison between a conventional reach stacker and the device according to the present invention, in order to show the difference in space requirement for the two devices. At the lower part of figure 12, a conventional reach stacker 100 is shown in the process of transporting a standard container 101, which has a length of 12192 mm. The space requirement is 100 mm either side. As seen, the reach stacker 100 requires a theoretical width of 13100 mm between container stacks 102 and 103 and 12400 mm between container stacks 103 and 104 in order to be able to turn with the container 101.

At the top of the figure, a container stacker 105 according to the present invention is in the process of transporting a container 106 with dimensions that correspond to those of the container 101. The container is carried on the area 115 or in the spreader 3, as explained in connection with figure 1. It is assumed that a clearing of 100 mm on either side will be required also in this case. Due to the particular design and swivel means of the container stacker 105 according to the present invention, the width required between container stacks 102 and 108 and container stacks 107 and 108 respectively is only 8700 mm, which is 4.5 m less than in the case of a conventional reach stacker. This corresponds to more than 1.5 times the width of a standard container, and is of considerable importance when it comes to utilising the available space in the container area.

A steering system for steering the container stacker described above will now be described.

The operator's cabin on the container stacker is preferably provided with a joystick instead of a wheel. Thus rotation of the upper part is controlled by sideways movement of e. g. a joystick located to the right of the operator, while the direction of driving is selected using a joystick located to the left of the operator. Upon starting up the machine, a computer will be set up in a manner such that a first movement of the left- hand joystick will cause the wheels to be oriented in the direction of the stick movement. I. e. the sets of wheels are rotated in the direction that results in the smallest angle based on the initial position. The correlation between stick deflection and driving direction is thus set. If the upper part is rotated while driving, by operating the right- hand lever, the machine will still continue to drive in the same direction, i. e. the stick deflection retains its direction in the operator's cabin and the direction of driving remains the same; however these may no longer necessarily coincide.

If the left-hand joystick is placed in the neutral position, the machine will stop. The computer will then zero the driving direction. When the left-hand stick is given a new deflection, the machine will drive in the same direction as that of the stick deflection, independently of any rotation of the upper part.

The stick is therefore a combined selector for direction of steering and selector for direction of driving, in the sense that the direction of the vehicle may be changed 180° either by letting go of the stick and then moving it in the opposite direction, or by letting the arrow direction of the stick deflection gradually change by 180°.

Although the above describes a device for handling of containers, the invention is not limited by this but may be used in connection with all types of load handling where this is appropriate.