EP4227255A1

EP4227255A1 - Material handling vehicle and method for operating a material handling vehicle

Info

Publication number: EP4227255A1
Application number: EP22156190.5A
Authority: EP
Inventors: Max HALLQVIST; Magnus Alveteg; Ali SHUMAN
Original assignee: Toyota Material Handling Manufacturing Sweden AB
Current assignee: Toyota Material Handling Manufacturing Sweden AB
Priority date: 2022-02-10
Filing date: 2022-02-10
Publication date: 2023-08-16

Abstract

Material handling vehicle (1) comprising a first load sensor device (8) that may detect the position including an angle of a load on a pallet as the load is carried by the load carrier (2) of the material handling vehicle (1). The disclosure also includes a method for operating a material handling vehicle (1) where the position of a load (21) is determined as the load (21) is carried by the load carrier (2). A software reproducing the method is also disclosed.

Description

The present disclosure is related to a material handling vehicle and a method for operating a material handling vehicle according to the appended claims.

BACKGROUND

In material handling operations in a warehouse situation, various types of material handling vehicles are used. Also, different racks are used for storage of pallets at level above ground level. In general material handling vehicles operate by transporting pallets to and from racks. In particular there are also racks positioned close to each other such that the aisle where the material vehicle is operating is narrow. There are likewise situations where the racks are easy reachable and not positioned close to another rack or wall, i.e. were the width of the aisle is not preventing operation of the vehicle more freely. In general, floo space is limited in a warehouse and thus it is desirable to use high racks in order to be able to store more goods on a defined ground space. For this reason many material handling vehicles are provided with lift devices in the form of forks operable by a hydraulic system in order to be able to handle loads on pallets at high levels, by lifting and lowering loads and then position the load with pallets in the rack, or remove a load with pallet from a rack at any level.
In general, a rack is constituted by two horizontal beams that is separated by a distance allowing for a load with pallet to be positioned horizontally on the beams when stored on the rack.
For reasons of safety, the loads on pallets need to be spaced from each other on the rack. If the loads were allowed to be positioned too close to each other a neighbouring load might hook up with a load that is to be introduced or removed from the rack. This could cause dislocation of the neighbouring load or even that the neighbouring load is moved so much that it looses contact with one of the horizontal beams and falls of the rack. This may of course damage the load on the pallet, but it also is a potential risk of injury to any person or vehicle being close by. As a solution to these problems, standards have been implemented for positioning of loads on pallets, one such standard is the EN15620. These standards are applicable for VNA - very narrow aisle - material handling vehicles. The standards are applicable for the racks and pallets positioned on these racks in a warehouse where VNA vehicles are operating.

SHORT DESCRIPTION OF THE INVENTION

It is becoming more and more desirable to operate automated guided material handling vehicles AGVs also in a warehouse. Automated vehicles are thus operable to move loads independently of an operator in a warehouse. In order to safeguard the operation, the present technology requires that pallets positioned by AGVs on a rack, are positioned at a larger distance between each load than corresponding loads positioned with manually operated vehicles. Thus, a specific area of floor space, may not store as many loads on pallets if AGVs is operating in that area, if compared to a situation where only manually operated material handling vehicles are operating.
Thus, there is proposed a material handling vehicle comprising, a load carrier, comprising a pair of forks. The material handling vehicle also comprises a control unit. A drive motor coupled to at least on drive wheel controllable by the control unit and powered by an energy source is also comprised. A hydraulic system, comprising at least one hydraulic pump, powered by a pump motor, and the necessary piping for powering hydraulic cylinders in particular for lifting and operating the load carrier, are also part of the proposed material handling vehicle. Further at least one pallet tunnel sensor device for determining position of at least one pallet tunnel of a pallet before engaging the pallet is comprised in the vehicle, wherein said pallet tunnel sensor device being arranged such that it may communicate with the control unit. Adjacent the load carrier and movable with the load carrier is positioned at least one first load sensor device, on the vehicle. The first load sensor device is coupled to the control unit in order to communicated with the control unit. Wherein after engaging a pallet with the load carrier, the material handling vehicle is arranged such that the first load sensor device may detect a first outermost point of a pallet and/or a load as the pallet and/or load is carried by the load carrier. The outermost point is defined as being in a horizontal direction away from the load carrier in perpendicular direction to the forks of the load carrier.
With the proposed vehicle the loads and/or pallets may have a reduced distance in between them. The material handling operation is thus improved, and more loads may be positioned on a predetermined area of a warehouse. Also, it is possible to achieve the reduced distance despite the many difficulties in tolerances within the material handling vehicle. The long mast will have both, rotational loads, rotational elongation, and also it is difficult to apply a base line for measuring when seeking to determine where a fork is and a load is in relation to a chassis of a material handling vehicle. Tolerances are added upon each other giving the requirements of the standards as discussed above, for the distances required between loads. By performing measurement on the load as it is engaged on the load carrier, any tolerance problems when measuring a pallet in the rack will be eliminated. For example, if the measurement of the load and/or pallet is made before engaging the pallet, as the vehicle moves and engages the load, the measurement may be obsolete by bending and movement of the mast, forks, etc. By determining the outermost point there is provided a basic knowledge that helps when moving and lifting a load and/or a pallet, in particular when setting down a load in a new position in the warehouse.
According to a further development there is proposed a material handling vehicle according to claim 2.
Advantage, by providing measurement on both sides of a load and/or pallet a more precise operation of the material handling vehicle is provided for. The load may be handled without damaging the load or pallet in this predetermined direction.
According to a further development there is proposed a material handling vehicle according to claim 3.
The detection operation on both sides of a pallet or load is much faster with dedicated load sensor devices. Also, the determined a second outermost point on an opposite side, allows for in a final manner determine the position of the load or/and pallet in the predetermined direction.
According to a further development there is proposed a material handling vehicle according to claim 4.
This provides for a very exact and simple determination of the outermost points, with a breach of the planes is defined as an outermost position. By arranging such that the plane may move towards the load from the side the detection is efficient and provides a simple way detect the outermost points as the plane does not need to change its angle as compared with a sensor device that for example has a rotating function to detect in different directions. If both load sensor devices are fixedly attached at a predetermined distance from each other and movable together, sensors may be positioned such that they may detect at the same time in the free spaces on the sides of a standardized pallet and/or load.
According to a further development there is proposed a material handling vehicle according to claim 5.
It is provided for a simple set up of the system if the vertical plane or planes extend along the same direction as the forks of the load carrier.
According to a further development there is proposed a material handling vehicle according to claim 6.
Laser sensor devices are very precise and may be configured easily.
According to a further development there is proposed a material handling vehicle according to claim 7.
By being able to move the load sensor device outside the back structure of the load carrier a broader volume may be scanned, and it is possible to detect objects that may obstruct movement of the pallet and or the load. The recessed position allows for a narrow scanning range that may determine also thinner loads, and also it prevents the load sensor device from obstructing movement of the load carrier in narrow spaces.
According to a further development there is proposed a material handling vehicle according to claim 8.
The load sensor device being arranged such that the outermost portion is determined at any height of the loads. This, thus provides for that the determination of the loads protruding features is improved. By using a vertical plane, it is possible to scan the load and pallet for the outermost objects at any level and very quickly.
According to a further development there is proposed a material handling vehicle according to claim 9.
The AGV makes the material handling automatic. And the use of the above load sensor devices provides for that the AGV may operate with the same tolerances of clearance between loads/pallets as a manually operated material handling vehicle.
There is also proposed a method for operating a material handling vehicle according to claim 10.
The advantage of the method is in line with the material handling vehicle as discussed above.
There is also proposed a method for operating a material handling vehicle according to claim 11.
The advantage of this is that the method also improves a movement of a pallet and/or load in a warehouse, and the determined position helps the vehicle to position the pallet and/or load in the new position.
According to a further development there is proposed a method according to claim 12.
By making a full determination of the outermost points of a first side and an opposite side the material handling vehicle may make calculations on how to position the load in a new position on a warehouse rack or the like.
According to a further development there is proposed a method according to claim 13.
The advantage is that by determining a centreline that is related to the position of the load or pallet and not to a geometrical centreline that is defined by measuring along the same direction for any load or pallet. I.e. along a direction that is parallel with the extension of the long side of a pallet and measuring perpendicular to this direction.
According to a further development there is proposed a method according to claim 14.
By using the centreline as determine a slot in a new warehouse rack may be fully used and the needed tolerances on each side of a pallet and/or load may be easily met.
And by using a load sensor device for determining a reference point it is made possible to be very exact when positioning the load. In this process the determined centreline of the load and/or pallet is very helpful, as it provides a tool for positioning the load and/or pallet, by for example using a predetermined centreline of the slot where the load and/or pallet as a reference for coinciding with the determined centreline.
According to a further development there is proposed a method according to claim 15.
By using a second load sensor device in the method a quicker and more effective determination of the outermost point's position may be achieved. And by moving the load sensor devices away from the load and/or pallet there are achieved the advantage of providing for using one or both of the load sensor devices to determine free space around the load and/or pallet, this being particularly important when delivering the load and/or pallet to a new position.
Further there is also proposed a software according to claim 16.
This provides for the method to be performed automatically.

LIST OF DRAWINGS

Fig. 1 discloses a material handling vehicle according to the disclosure with the load carrier in a right home position.
Fig. 2 discloses a standard pallet from a short side and from above.
Fig. 3 discloses a load carrier with the first and second load sensor device in extended position.
Fig. 4 discloses a load carrier with the first load sensor device in an extended position and a second load sensor device in a recessed position.
Fig. 5 discloses a pallet as engaged by the load carrier according to the disclosure.
Fig. 6 discloses a warehouse rack including pallets and loads.
Fig. 7 discloses a material handling vehicle according to the disclosure with the load carrier in a forward position.
Fig. 8 discloses a material handling vehicle according to the disclosure with the load carrier in a left home position.
Fig. 9 discloses a material handling vehicle according to the disclosure, detecting the pallet tunnels of a pallet carrying a load.
Fig. 10 discloses a material handling vehicle according to the disclosure detecting the pallet tunnels of a pallet that is in a twisted position, also carrying a load.
Fig. 11 disclosure a material handling vehicle according to Fig. 10 engaging the pallet and load with a twisted position.
Fig. 12 discloses a material handling vehicle according to Fig. 11, with the pallet and load in a twisted position during the determination of the position of the pallet and load on as it is being carried by the load carrier.
Fig. 13 discloses a method according to the disclosure.
Fig. 14 discloses initiating to position a load in a slot of a rack.

DETAILED DESCRIPTION

AGV-Automated Guided Vehicle, is arranged to be able to operate in a warehouse independently of manual instructions from an operator. The AGV may also include manual control functions such as a joystick, steering wheel, brake pedal, accelerator pedal etc., such that it may be operated manually also. But also the AGV may lack all such devices, and for example only be operable manually by means of a remote control.
The disclosure is related to an AGV having a load carrier device for handling pallets. The load carrier device includes a pair of forks.
In general, the AGV is a material handling vehicle. The vehicle has a load carrier, comprising a pair of forks. The forks are intended to be inserted into pallet tunnels of a pallet. The pallet tunnels comes often with standardized shape, but may have various shapes. In general the opening and the tunnels have a rectangular section. On the pallet is a load positioned. The load may have many different shapes, but in general it can be defined as a box with the outer dimensions being parallel with the pallet horizontal surface. However, the load may extend outside the pallet, in particular when on occasion the loading of the pallet was derogatory from the desired loading. The height of the load is more or less determined by the rack dimensions, thus a load may have a maximum height. Also the load may have a maximum width, and maximum length. The weight of the load may also have a maximal allowed value. A pallet is in general made in wood hand has a long side and a short side. The short side having two pallet tunnel openings. The pallet tunnels extending along the length of the pallet in a parallel manner. Thus, having a further two pallet tunnel openings on the other short side of the pallet. This is the general definition of a pallet. Horizontal surface is thus the surface that a pallet will occupy when positioned on a floor in with its two long sides and short sides reaching the floor.
The AGV is provided with a control unit. In defining the control unit it should be understood that a control unit may be several hardware processors and memory etc., that are located at different locations in the AGV. Thus, the control unit may be distributed intelligence hardware. All hardware of the control unit is arranged to be able to communicate with hardware on the AGV. There may also be a display device that is connected to the control unit, primarily for service and support purposes.
The AGV has preferably a CAN bus system that is arranged throughout the vehicle for communication purposes of the components and devices of the vehicle, such as sensors, lighting, hydraulic system, pressure sensors, drive motor, rpm sensors etc.
The AGV is provided with a drive motor. In general, a single drive motor is provided to a centrally positioned drive wheel. The drive wheel being arranged to be steerable along a steering axis, for manoeuvring the AGV. However, it is possible to have more than one drive motor. The motor then being arranged to drive a non-turning wheel on one long side of the AGV, and a second motor is then arranged to a second non-turning wheel on a second long side of the AGV such that the vehicle may be manoeuvred by rotating the drive wheels at different rotation velocities, or even in a counter rotating procedure for turning on the spot.
The AGV is provided with a pallet tunnel sensor device. The pallet tunnel sensor device may be a laser scanning device which is arranged to detect pallet tunnels and determine that these are situated on the same pallet, and not for example a pallet tunnel on a first pallet and a second pallet tunnel on an adjacent pallet. The pallet tunnel device may be a sensor that detects and has a memory that may compare and determine if a pallet tunnel is fulfilling the predetermined criteria. The pallet tunnel sensor device may also be based on optic technology, such as a camera device.
The AGV is provided with a load sensor device. The AGV may have a first and second load sensor device. Thus, having the ability to detect the load position on both a first long side and a second long side of the pallet.
The AGV determines a position of a load and/or pallet. Thus, the load sensor device may when a load has been lifted by the forks determine the position of the load on the load carrier. The load sensor device may detect if there are protruding sections, i.e. points, of the load itself. This means sections, points that protrudes outside the horizontal area of the pallet.
The load sensor device or devices is arrange to be able to detect objects in a vertical plane. This means that any object protruding into the plane is detected.
The present disclosure is related to the possibility to detect a position for a load.
The present disclosure is related to the possibility to detect the shape or at least the most protruding sections of a load compared with a standard plane or standard load, which has been discussed as being a volume with the shape of a box.
The present disclosure allows for providing an AGV that is performing very narrow aisle operation with a pallet position distance that is equal to a pallet position that is achieved by a manually operated VNA material handling vehicle.
The present disclosure is thus related to a material handling vehicle 1 as disclosed in Fig. 1. The directions of the material handling vehicle 1 is disclosed in Fig. 1 by the X direction, i.e. the longitudinal direction, and the Y-direction, i.e. the transversal direction of the vehicle 1.
The material handling vehicle 1 comprises a load carrier 2, with a pair of forks 3. The load carrier as exemplified in Fig. 1 may be movable both up and down. The load carrier 2 may also be movable in the transversal Y direction of the material handling vehicle 1. In some material handling vehicle the load carrier 2 may be movable in the X direction.
A control unit 4, see Fig. 1, is also comprised on the material handling vehicle 1. The control unit 4 is arranged such that it may control the vehicle in operation, without interaction of an operator. That is the control unit may store an execute software that controls all functions of the normal operation of the material handling vehicle 1. Even if the control unit 4 is disclosed in singular. The control unit 4 may be a control unit assembly where several smaller control units cooperates in the control of the functions of the vehicle 1.
There is also comprised a drive motor 5 for movement of the vehicle. The drive motor may be fixed and drive one or several wheels. In a preferred embodiment the drive motor 5 is applied with a gear box such that the drive wheel 5 may rotate and control the direction of travel of the material handling vehicle 1.
The vehicle has an energy source 35. This may be a battery. The battery may in particular be a Lead Acid battery which provide good stabilizing properties due to its weight. The battery may be a Lithium Ion battery, which provide very good charging capability and high capacity.
There is also comprised further a hydraulic system 36, Fig. 1. The hydraulic system 36 comprises the normal components for a material handling vehicle 1, such as a pump 37, a pump motor 38 and piping for powering hydraulic cylinders. The cylinders being used mainly for moving and operating the load carrier 2 of the vehicle.
In general, standardized components of a material handling vehicle 1 is comprised also for the disclosure. In particular there is a main mast 39 comprised. The main mast 39 is thus extending upwards and thereby it is possible to lift the load carrier 2 to considerably heights. For a very narrow aisle material handling vehicle 1, there is may also be comprised secondary mast. The optional secondary mast may thus comprise the load carrier 2 and may initiate lifting from the floor up to about a normal load height. The secondary mast may be moved along the transversal Y direction of the main mast. There may also be as disclosed in Fig. 1 a boom 40 that moves along the Y direction carrying the load carrier 2 and allowing for the load carrier to rotate according to Fig. 1, 7 and 8. Thus, the initial lifting from a floor position may thus be made by lifting the boom 40 together with the load carrier 2 and the complete rotational fork assembly 45, that is the load carrier 2, the boom 40 and the frame 44.
For the operation of the vehicle 1 it is possible to discuss a home position for the load carrier 2. Fig. 1 discloses a first home position. Fig. 8 discloses a second home position. Fig. 7 discloses a third possible home position. When the load carrier 2 is in the home position, the material handling vehicle may move without risking that the load carrier interferes with objects in the warehouse during movement.
The material handling vehicle 1 may also comprise a bus system for communication within the vehicle 1. There may thus be a CAN-bus system that connects the various devices, sensors etc. with the control unit 4.
The material handling vehicle 1 comprises a pallet tunnel sensor device 7, Figs. 1 and 3, 4, 5. The pallet tunnel sensor device 7, is arranged such that it may detect at least one, preferably two pallet tunnels 26, 27 of a pallet 20 as disclose in Fig. 2. The pallet tunnel sensor device 7 may be a laser detection device. The pallet tunnel sensor device 7 is preferably attached in a central position on the back of the load carrier assembly. In this position the pallet tunnel sensor device 7 may detect both a first pallet tunnel 26 and a second pallet tunnel 27 with the same sensor device 7. The pallet tunnel sensor device 7 is connected to the control unit 4 for receiving instruction data from the control unit 4 and also for sending detection data to the control unit 4. The pallet tunnel sensor device 7 is movable with the load carrier 2, but fixedly attached to the load carrier backing structure 32.
On the load carrier 2 there is comprised a first load sensor device 8. The first load sensor device 8 as disclosed in Fig. 3 may be attached to the back structure 32 of the load carrier 2. The first load sensor device 8 is movable in transversal direction of the load carrier 2. This movement may be arranged for example by means of a screw transport device 8a. The screw transport device may be replaced by another actuator device, for example a hydraulic cylinder in combination with a track that the movable first load sensor device 8 moves in. The first load sensor device 8 is preferred to be a sensor device that may detect in an essentially vertical plane 27. By moving the sensor device 8 in along the screw transport device the vertical plan 27 moves towards or from a load 21, fig 6, Fig 12, in transversal direction of the load carrier. In Fig. 1 the transversal direction of the load carrier 2 is parallel with the X-direction.
The first load sensor device 8 is preferred to be a laser sensor device. The detection thus is made on a load 21, Fig. 12 or a pallet 20. The important arrangement of the first load sensor device 8 is to arrange it such that it may detect the outermost point, i.e. section, e.g. the outermost section or area of the load 21 and/or pallet 20. In fig. 5 the pallet discloses a first outermost point 11. By moving the load sensor device 8 along the back structure 32 of the load carrier 2, the first point detected will on the left side in Fig. 5, if the first load sensor device 8 is moved from an outermost position as disclosed in Fig. 3, towards the load 21 and/or pallet 20. If the load 21 is broader than the pallet 20, the first outermost point detected 11 will be on the load 21 and not on the pallet 20. Fig. 6 discloses an exemplified load 21 that is broader than the pallet 20. The movement direction is thus, along the perpendicular direction to the extension of the forks 3 of the load carrier.
As the load carrier has engaged the load and/or pallet 21, 20, when the first load sensor device 8 determines the position of the load in relation to the load carrier, the load sensor device 8 moves a first distance 41, thereby moving the vertical plane 27 the same distance, Fig. 12. This makes it possible to determine a position of a first outermost point 11. Thus, the load sensor device 8, with its vertical plane 27 being parallel with the extension of the forks 3, may scan along the perpendicular direction of the forks 3 of the load carrier 2. Thus, a movement from a first position to a detection position of point 11, may be achieved.
In a variant the first load sensor device 8 may then move to the opposite side of the load 21 or pallet 20 and move back a corresponding distance to 41 and determine the position of a second outermost point 13, by moving a distance into position 43 of Fig. 12. A centreline 12 that is related to the position of the pallet 20 and/or load 21, may thus be determined, Fig 5 and Fig. 12. The determined centreline 12 may thus be positioned in a different location than a geometric centreline 12a. The determined centreline 12 may in a special case fall together with the geometric centreline 12a, if the load is positioned centred from all directions on the load carrier 2. The centreline 12 being defined as half of the distance between a vertical plane 27 when detecting point 11 and a vertical plane 28 when detecting point 13, as seen in Fig. 12.
A second load sensor device 9 may be applied at the opposite end of the back 32 of the load carrier 2, Fig 3. The second load sensor device 9, may have the same properties and technical specification as the first load sensor device 8. The difference between the second load sensor device 9 and the first load sensor device 8 being that the second load sensor device 9 is arranged to detect on the opposite side 31 of the load 21 or pallet 20. The second load sensor device 9 may thus detect in a second plane 28, that is preferred to be vertical.
In fig. 5 the pallet 20 is rotated an angle 10, 10a to a line extending in line with the forks 3 of the load carrier. This presentation is merely made as an example. The pallet after engaging and lifting may be parallel to the forks 3, but for example dislocated in an offset position to either side of the centre position of the forks 3.
As exemplified when the first and second load sensor devices 8, 9 work in pairs, they may be centred after determining the first and second outermost points 11, 13. That is they are centred on a respective side from centreline 12, at a distance from this centreline that will give a space corresponding to the lowest allowable tolerance according to the ruling standard of positioning loads in a warehouse, in particular on a warehouse rack 33.
The vertical plane 27 or planes 28 is thus movable in horizontal direction, as the sensor or sensor devices 8, 9 are movable in horizontal direction. The planes 27 and/or 28 are thus used for detecting along the first side 30 and/or second side 31 of the load 21 or pallet 20. Thus, not only the outermost points of a pallet 20 or load 21 may be detected. For example, the first load sensor device 8 in Fig. 5 may scan along the complete side 30, thus not only detecting the outermost points 11 and 13.
The first and/or the second load sensor device 8, 9 may be movable to extend outside the side of the back structure 32 of the load carrier 2. Thus, being able to move the vertical plane 27 outside what is the general position of a load 21 or pallet 20. Thus, in a warehouse rack 33, Fig. 6, the structures on the sides for example load 22, and beam 34 may also be detected before removing the load 21 from the rack 34. This is exemplified in Fig. 9 where the planes 27 and 28 may detect in the areas to left and right of the load 21. Thus, the extended position II of the first load sensor device 8 extends outside the perimeter of the back structure 32 of the load carrier 2, Fig. 4. And the recessed position I the first load sensor device 8 is within the outer perimeter of the back structure 32, Fig 4. This may be an advantage as there sometimes may be limited space in the warehouse in particular inside a rack or if a rack is close to a wall. Or situations where the material handling vehicle 1 is operating close to a wall or seeking to pick up a pallet 20 when in home position of Fig. 7.
The first and second load sensor devices 8, 9 may be arranged in a work in a pair configuration. That is, they may be arranged to move in linear direction along the back structure 32 of the load carrier 2 in a parallel manner, as seen in Fig. 4, were both load sensors devices 8, 9 is disclosed as moved from a first position I to a second position II. In a preferred way this pair movement may be achieved by attaching both the sensors to a common element that movable in the required direction. The element may be a rod that with a thread, such that the rotation is provided by rotation of the thread in a thread seat. The distance between the load sensor devices 8, 9 in this configuration, may advantageously be broader than a standardized load, for example the vertical planes 27, 28 may be at a distance of 820-1000 mm from each other, for example 840 mm or 850 mm or 860 mm. Thus the material handling vehicle 1 is arranged such that both load sensor devices 8, 9 may detect at the same time along a correctly positioned load 21 and/ or pallet 20, as they are standardized to 800 mm. This detection is then made in the free space around the standardized pallet 20 and/or load 21, Fig. 14.
As discussed, the outermost points the load 21 and/or pallet 20 is detectable by the material handling vehicle 1. This is as discussed exemplified in Fig. 5 with outermost points 11, 13. It should be stressed that the load sensor device 8 or 9 are arranged to detect the outermost point of a load at any height of the load. Thus, also the outermost position is defined in lateral direction outwards from the forks 3. It should also be understood as with the exemplified load 22 and pallet 20a, the outermost point 11a on one side may arise from the load 22, and on the opposite side 13a the outermost position may be the pallet 20a, Fig 6.
Fig. 13 discloses the main steps of the method according to the disclosure for operating a material handling vehicle 1. The method comprises thus the method of scanning a pallet 20, Fig. 2 in order to detect a pallet tunnel or both pallet tunnels 26, 27. This is made by the pallet tunnel device 7 as described above, Fig. 9, Fig 10. By this scanning it the material handling vehicle 1 may adapt the position of the load carrier 2 for engaging the pallet 20 with the load carrier 2. Thus, for example it is possible to adapt the position of the load carrier if the pallet 2 with the load 21 is rotated in the warehouse rack 33.
In a further step there is a scanning made by one load scanning device 8, preferably by also a second load scanning device 9. This scanning thus determines that the load 21 does not prevent the load 21, and pallet 2, to be removed from the warehouse rack 33, Fig. 9. It may be so that the load has been moved unintentionally after being positioned on the warehouse rack 33. It may also be so that this scanning step helps the material handling vehicle 1 to position the load carrier 2 more precisely before engaging the load.
In an ensuing step the material handling vehicle 2 is engaging the pallet 20 by extending the load carrier 2, i.e. the forks 3 into the pallet tunnels 26, 27, see Fig 11. This engaging step may be performed by moving the load carrier is extended in lateral direction Y as related to the material handling vehicle's longitudinal direction X, Fig. 1. It should be understood that this may also be achieved by moving the material handling vehicle 1, for example in longitudinal direction X, if the load is picked up in X direction, Fig. 7.
As the load 21/pallet 2 is engaged and lifted the load carrier 2 is moved out of the rack and there is performed a step of detecting the position of the load/pallet on the load carrier 2, see Fig. 11 and in particular Fig. 12. In Fig. 12 the scanning by the first load scanning device 8 and a second load scanning device 9 is performed. This is illustrated by double arrows in X direction of Fig. 12. Thus, a plane 27 or 28 from the load scanning device 8 is moved in X direction of Fig. 12 until an first outermost point 11 of the load 21 or pallet 20 is extending into the scanning plane 27. The moving is made possible by moving the first sensor device 8 along the transversal direction of the forks 3, as is exemplified in Fig. 3, and in particular Fig. 4 where a transversal movement from position I to position II is illustrated.
It should be understood that a single first sensor device 8 may be arranged to be used for making the detection on both sides 30, 31, Fig. 2, of the pallet 2 and/or load 21. This may for example be arranged, as mentioned above, by allowing for the first sensor device 8 to travel in transversal direction to the forks 3 from the first side 30 to the second side 31 of the load 21 or pallet 2 by allowing the full travel of the first load detecting device 8 from the fist side 30 to the second side 31, that is in Fig. 1 in X direction. In this example the first load detecting device 8 is also detecting the plane 28 on the opposite side of the pallet 20 and/or load 21, for detecting also the second outermost point 13 of the pallet and/or load.
In an alternative of the method the steps of

transporting the pallet 20 and/or load 21 to a new position in a warehouse,
positioning the pallet 20 and/or load 21 in the new position using the determined position of the pallet 20 and/or load 21 for positioning the pallet in the new position.

This detection of the outermost points 11, 13 as exemplified in Fig. 5 and 6 is the point of the load and/or pallet that sets the largest footprint that the load 21 and pallet 20 occupies when viewing the load/or pallet in vertical direction. Thus, this will aid the material handling vehicle as it transports the load 21 or and pallet 20, and positions it at a new position in the warehouse. Also, the material handling vehicle 1 may thus adapt the delivery to a new position in the warehouse such that the load and/or pallet may be positioned in a more straight, efficient manner.
In doing this a more precise set of data for the position on the load carrier is determined.
The method may also comprise the step of:

Determining a centreline 12 position of the pallet 20 or load 21 in relation to the load carrier 2 in transverse direction, preferably this is being half the distance between the first outermost point 11 of one side and the second outermost point 13 of the opposite side of the pallet 20 and/or load 21.

There may also be the step of:

using the determined centreline 12 position for mediating the load into a new position in the warehouse.

When setting down a load in the rack the centreline 12 as determined will be very beneficial for allowing for a free space on both sides of the load when setting down the load in a rack 36.
There may also be the step of:

detecting the second outermost point 13 by means of a second load sensor device 9.

The detection may be made in parallel on both sides of the pallet/load for a quick and swift determination.
The material handling vehicle 1 may be arranged such that the first and second load sensor devices 8, 9 after determining the respective outermost points 11, 13 on opposite sides of a load and/or pallet, will move away from the load and/ or pallet such that they may monitor that a free space is available outside said load and/or pallet, wherein said free space correspond to a predetermined distance from the respective outermost points 11, 13 to the a vertical plane parallel with the extension of the forks 3 of the vehicle 1.
In the example of Fig. 4 the first and second load detection device 8 and 9 are moved in tandem in the same direction. This is only illustrated by way of example. The two load sensor devices 8, 9, may be arranged to move independently of each other as in fig. 3 where they are both protruding outside the load carrier 2.
There may also be a sequence of method steps made possible by the above arrangement and material handling vehicle 1, when setting of a load/pallet 21, after having engaged and determined the outermost points 11, and 13 and the centreline 12. Thus, as the vehicle 1 travels along the rack where it is to position the load 21 of Fig. 14, a vertical beam 46 is taken as a reference point. From the reference point, a predetermined distance 47 may be travelled by the vehicle 1. The load sensor devices 8 and/or 9 may be used in this process, by detecting the beam 46. The load and/or pallet is preferably determined to be in position for being set down when the centreline 12 as determined coincides with the centreline 47 of the slot where the load 21 is to be positioned.
The above discussed method steps are intended to be performed by the material handling vehicle 1 independently of any operator. This is made possible by arranging a software that is stored on a control unit 4 that may control the material handling vehicle 1.

Claims

Material handling vehicle (1) comprising,
a load carrier (2), comprising a pair of forks (3),

a control unit (4),

a drive motor (5) coupled to at least on drive wheel (6) controllable by the control unit (4),

an energy source (35) for powering the vehicle,

a hydraulic system (36), comprising at least one hydraulic pump (37), powered by a pump motor (38), and the necessary piping for powering hydraulic cylinders in particular for lifting and operating the load carrier (4),

at least one pallet tunnel sensor device (7) for determining position of at least one pallet tunnel (26) of a pallet (20) before engaging the pallet,

said pallet tunnel sensor device (7) being arranged such that it may communicate with the control unit (4),

characterised in that

adjacent the load carrier (2) and movable with the load carrier (2) is positioned at least one first load sensor device (8),

wherein the first load sensor device (8) is coupled to the control unit (4) in order to communicated with the control unit (4),

wherein after engaging a pallet (20) with the load carrier (2), the material handling vehicle (1) is arranged such that the first load sensor device (8) may detect a first outermost point (11) of a pallet (20) and/or a load (21) as the pallet (20) and/or load (21) is carried by the load carrier (2), the outermost point (11) is defined as being in a horizontal direction away from the load carrier (2) in perpendicular direction to the forks (3) of the load carrier (2).
Material handling vehicle of claim 1, wherein the material handling vehicle (1) is arranged such that the first load sensor device (8) may detect a second outermost point (13) of the pallet (20) and/or load (21) on the opposite side of the pallet (20) and /or load (21).
Material handling vehicle (1) of claim 1 or 2, wherein a second load sensor device (9) is provided on the opposite side of the load carrier (2) to the first load sensor device (8), the second load sensor device (9) being arranged to detect the second outermost point (13) of the pallet (20) and/or the load (21).
Material handling vehicle (1) according to claim 3, wherein the first and/or second load sensor device (8, 9) is arranged to be movable in horizontal direction on the load carrier (2), such that the vertical plane (27, 28) may be moved in horizontal direction in relation to the load carrier (2), preferably the first and the second load sensor devices (8, 9) are fixedly attached at a predetermined distance from each other such that they move together in horizontal direction, even more preferred the predetermined distance is longer than a predetermined transversal dimension of a standardized pallet (20) and/or load (21).
Material handling vehicle (1) of any of the claims above, wherein the first and/or second load sensor device (8, 9) are arranges such that it/they may detect in a vertical plane (27, 28) that extends along the same direction as the forks (3) of the load carrier (2) are extending.
Material handling vehicle (1) of any of the claims above, wherein the first and/or second load sensor device (8, 9) is constituted by laser sensor devices.
Material handling vehicle (1) according to any of the claims above wherein the first and/or second load sensor device (8, 9) is arranged to be movable from a first extended position (I), to a second recessed position (II), in relation to the load carrier (2).
Material handling vehicle (1) according to any of the claims above, wherein the first and/or second load sensor devices (8, 9) is/are arranged such that the detected outermost portion/s (11, 13) of the pallet (20) and/or load is positioned at any vertical position from bottom of the pallet (20) to the top of the pallet (20) and/or load (21).
Material handling vehicle (1) according to any of the claims above, wherein the material handling vehicle (1) is an automated guided vehicle, AGV.
Method for operating a material handling vehicle comprising the steps of:
- detecting at least one pallet tunnel (26) of a pallet (20) with a pallet tunnel sensor device (7),

- engaging and lifting a load (21) by inserting a load carrier (2) into the at least one detected pallet tunnel (26),

- detecting the position of a pallet and/or a load on the load carrier (2) by a first load sensor device (8),
wherein, the detected position comprises a first outermost point (11) of the pallet (20) or load (21) in relation to the load carrier (2), preferably the first load sensor device (8) uses a vertical plane (27) for the detection of the outermost point (11).
Method according to claim 10 comprising the steps of:
- transporting the pallet (20) and/or load (21) to a new position in a warehouse,

- positioning the pallet (20) and/or load (21) in the new position using the detected position of the pallet (20) and/or load (21) on the load carrier (4).
Method according to claim 10 or 11, comprising the steps of:
- detecting a second outermost point (13) of the pallet (20) and/or load (21) on a second side (31) being the opposite side of the pallet (20) and/or load (21).
Method according to claim 12 comprising the step of:
- determining a centreline (12) position of the pallet (20) or load (21) in relation to the load carrier (2) in transverse direction, preferably this is being half the distance between the first outermost point (11) of one side (30) and the second outermost point (13) of the opposite side (31) of the pallet (20) and/or load (21).
Method according to claim 13, comprising the step of:
- using the determined centreline (12) position for mediating the load into a new position in the warehouse,
preferably said new position is determined to be reached when a centreline (47) of the new position coincides with the determined centreline (12) of the load (21) and/or pallet (20), even more preferred using one of the load sensors (8) for determining a reference point of a rack comprising the slot, such that the vehicle may travel a predetermined distance (48) from the reference point along the rack to the position where the two centrelines (12, 47) coincides, most preferred said reference point comprises a vertical beam (46) of the rack.
Method according to any of the claims 12-14, further comprising the steps of:
- detecting the second outermost point (13) by means of a second load sensor device (9), preferably the first and second load sensor devices (8, 9) after determining the respective outermost points (11, 13) on opposite sides (30, 31) of a load and/or pallet, will move away from the load and/ or pallet such that they may monitor that a free space is available outside said load and/or pallet, wherein said free space correspond to a predetermined distance from the respective outermost points (11, 13) to the a vertical plane parallel with the extension of the forks 3 of the vehicle (1).
Software that when stored on a control unit of a material handling vehicle (1) is arranged to execute the method according to any of the claims 10-15.