SE541657C2 - Fork-lift truck and a method for operating a fork-lift truck - Google Patents

Abstract

Fork-lift truck (1) comprising, a load carrier (2) and a load carrier control unit (5), a control aid device (8,9), wherein the load carrier (2) is provided with at least one detecting device (10a), wherein the detecting device (10a) is arranged to be able to send out a signal and receive an echo signal from a first load feature (4a), wherein the detecting device (10a) is arranged to be able to send an output data based on the received echo signal, to the load carrier control unit (5), wherein the load carrier control unit (5) is arranged to be able to, based on the received data, determine a relative position of the load carrier (2) in relation to the first load feature (4a) and to provide a control output, based on the determined relative position, to a control aid device (8, 9), wherein the determined relative position corresponds to a point (26) on a plane (25) that is defined as extending in a perpendicular direction to the central axis (4c) of the first load feature (4a). Further a method for modifying and operating a fork-lift truck is also disclosed.

Description

FORK-LIFT TRUCK AND A METHOD FOR OPERATING A FORK-LIFT TRUCK The present invention relates to a fork-lift truck according to claim 1. The present invention also relates to a method for operating a fork-lift truck according to claim 9.

BACKGROUND In operation of a fork-lift truck an operator navigates in warehouses and other material handling locations. When operating the fork-lift truck the load carriers is operated in all directions, up, down, forward, and backwards. Loads are often positioned on pallets. It is known to provide fork-lift trucks with aids in order to simplify operation. One such fork-lift truck is known through the document JP2002-087793 A where a complex system of sensors is provided on the fork-lift truck in order to precisely determine distances from the fork to the pallet tunnels in longitudinal direction by using a system of two different types of sensors. The document also discloses measuring even further ahead distances to other palettes, apparatus etc.

US6150938 A and US3672470 disclose the state of the art with regard to optical guiding.

BRIEF DESCRIPTION OF THE INVENTION When operating the fork-lift truck it is not uncommon that the operator has difficulties to see the load carrier and the pallet from the position at the controls of the fork-lift truck. The ergonomic operation of the fork-lift truck is jeopardized when the operator is obliged to leave his position in order to determine if he can engage a pallet or not. In particular it is difficult where the pallet is positioned high above the operator on a pallet rack.

The prior art fails to disclose a simple aid to an operator that offers assistance at the last part of adjusting the forks in lateral direction when engaging a pallet or a load with a pallet configuration. And previous technical solutions still require free sight to the load or pallet, and the work position for the operator is thus not optimized, as he need to have free line of sight to the pallet.

In order to solve at least one of the drawback mentioned there is suggested a, fork-lift truck comprising, a load carrier and a load carrier control unit , a control aid device, wherein the load carrier is provided with at least one detecting device, wherein the detecting device is arranged to be able to send out a signal and receive an echo signal from a first load feature, wherein the detecting device is arranged to be able to send an output data based on the received echo signal, to the load carrier control unit , wherein the load carrier control unit is arranged to be able to, based on the received data, determine a relative position of the load carrier in relation to the first load feature and to provide a control output, based on the determined relative position, to the control aid device, wherein the determined relative position corresponds to a point on a plane that is defined as extending in a perpendicular direction to the central axis of the first load feature.

The advantage of the above fork-lift truck is that the operation of it is simplified. The fork-lift truck also prevents damaging of the loads to be handled, by giving indication to the operator of the relative position of the load carrier and the load features. The operator is considerably helped when finalizing the adjustment operation of the load carrier in view of engaging a load. The operator is thus experiencing a fork-lift truck that is more ergonomic to operate. And importantly the operator gets the important information regarding the relative position of the load carrier when he is close to his pallet/load. That is he does not get additional information that can distract him when engaging a load/pallet.

According to a further development the control aid device comprises a sound device, wherein said sound device is operable with the load carrier control unit, for giving a sound output that is detectable by an operator, based on the control output from the load carrier control unit.

The advantage of this is that the operator need not have any visual contact with an instrument or the load carrier or the load features, and still he will get an indication, or help to adjust his load carrier, when he is close to the load or pallet.

According to a further development the sound output is arranged to be different with regard to at least two different predetermined relative positions, such that a specific relative position of the loadcarrier is detectable by an operator.

The advantage of this is that the operator can precisely position the load carrier in relation to the load features without having a direct view of the load carrier and the load features. It is thus possible for the operator to conduct several tasks at the same time. He is also aided such that he will get an acknowledgement that he has positioned his load carriers in the desired position. Thus even if he does view the load features and the load carriers he will through the sound device achieve an acknowledgement that helps him to operate in a more ergonomic, safe and fast way.

According to a further development the control aid device comprises a display device, wherein the display device is operable with the load carrier control unit, for giving an output to the display device, that is detectable by an operator, based on the control output from the load carrier control unit, preferably the display device is located at/or within the operators position at operation of the forklift truck.

By also having a display device that can provide a message on a display to an operator the indication given by the fork-lift truck is detectable by sight, this further has the advantage that the indication is not subject to the hearing ability of the operator or the sound disturbances that can vary considerably between different load positions.

According to a further aspect of the fork-lift truck, the load carrier control unit is comprised within a main control unit of the fork-lift truck.

The advantage of this is that no further hard-ware is needed for the control functions. The capacity of the on board main control unit, i.e., the main computer, can be used. This is in most cases cost effective.

According to a further aspect of the fork-lift truck, the load feature is the boundary of a pallet opening intended to receive the load carrier.

By using the openings boundary of a pallet that is intended to receive the load carrier, the detecting devices focus on the features that also are to be engaged of the load carrier. As the boundary of the opening is always present, this feature is particularly useful for detecting the relative position. In general the dimension of the boundary of the opening are more or less standardized, thus it is particularly easy to calibrate the detecting devices and the load carrier control unit for the intended usage. It is also preferred to use the boundary of the opening as these have both an upper, lower and left and right border periphery that can be used for monitoring the echo signal from the load features by the detecting devices.

According to a further aspect of the fork-lift, the said plane is defined to tangent the end side of a load pallet comprising said first load feature.

By determining the position on a plane that is defined to tangent the end side, this simplifies for the operator as he only needs to adjust the load carriers in lateral direction of the load feature. Lateral is to be construed as meaning from the side our from above or below in direction to the central axis of the load feature.

According to another aspect of the fork-lift truck the load carrier comprises two forks, wherein the detecting device is positioned on one of the forks, preferably closer to the outer end of the fork.

The advantage of positioning the detecting device closer to the outer end is that the distance between the detecting device and the load features are minimized. Thus the resolution of the detecting signal and echo signal of it are optimized as the resolution will increase the closer the detecting device is positioned with regard to the load features. According to a further aspect of the fork-lift truck, wherein the load carrier comprises a second detecting device, that is positioned in transversal direction of the first detecting device on said load carrier , wherein the second detecting device is arranged to be able to send out a signal and receive an echo signal from a first load feature or second load feature, wherein the second detecting device is arranged to be able to send an output data based on the received echo signal, to the load carrier control unit, wherein the load carrier control unit is arranged to be able to, based on the received data, determine a relative position of the load carrier in relation to the first load feature a and/or the second load feature and to provide a control output, based on the determined relative position, to the control aid device, , wherein the determined relative position corresponds to a point on a plane that is defined as extending in a perpendicular direction to the central axis c of the first load feature and/or a central axis d of the second load feature.

The advantage of providing a second sensor is that the relative position of the load feature or load features can be determined more precisely. There is a further output that can detect and give further information. It is also possible to determine the relative position for example based on a left side of the first load feature base on the first detecting device's output data, and the right side of the first load feature on the second detecting device's output data. It is also possible to do this but instead use the corresponding left side of the second load feature for a more precise transversal determination of the load carrier's relative position.

According to a further aspect of the fork-lift truck, the load carrier control unit is arranged to make a calculation based on both the outputs received from the first detecting device and the second detecting device, for a more precise determination of the relative position of the load carrier in relation to the load feature and/or load feature.

The advantage is a more precise determination of the relative position.

According to another aspect of the fork-lift truck the detecting device is an ultrasonic sensor or the detecting devices, are ultrasonic sensors.

Ultrasonic sensors are particularly easy to handle. They are rugged, well developed and can withstand any lighting condition in the area where the fork-lift truck is operating. The ultrasonic sensors are cost effective. The ultrasonic sensors do not derange or affect the operator or other persons operating in the vicinity of the fork-lift truck. Ultrasonic sensors also have a relatively wide angle of functioning, such that even if the sensor is displaced slightly it still operates well.

According to another aspect of the fork-lift truck the detecting device is a laser sensor or the detecting devices are laser sensors.

Laser sensors are very accurate. Thus the determination of the relative position can be very accurate for applications where accuracy is important, for example when handling fragile loads.

According to a further aspect there is provided a method of modifying a fork-lift truck, comprising the steps of: - provide a fork-lift truck, - modify the fork-lift truck of the previous step such that it is configured as in any aspects above.

The advantage of modifying an existing fork-lift truck is that the ergonomics of an older fork-lift truck can be improved. A further advantage is that if a fork-lift truck in a particular application is determined to be more exposed to damages of loads or itself, it can be modified by the method in order to lower the damages of it and loads, etc.

According to a further aspect there is provided a method for operating a fork-lift truck according to any of the aspects above, comprising the steps of: 51. providing a fork-lift truck comprising a load carrier provided with at least one detecting device and providing a load comprising at least one load feature, 52. approaching the load with the load carrier of the fork-lift truck, 53. sending out a signal from the detecting device and, 54. receiving an echo signal from the at least one load feature by the detecting device, 55. sending an output data based on the received echo signal to a load carrier control unit, 56. determining the relative position of the load carrier with regard to the load feature, by the load carrier control unit, based on the received data, wherein the determined relative position corresponds to a point on a plane that is defined as extending in a perpendicular direction to the central axis of the load feature, 57. providing a control output from the load carrier control unit to a control aid device of the fork-lift truck based on the relative position detected, 58. adjusting the relative position of the load carriers based on an output from the control aid device.

The advantage of operating a fork lift truck according to the method is improved ergonomics, safer, faster and easier handling. The operator can focus on performing other tasks than positioning the load carrier.

Further aspects of the invention will be apparent for the detailed description and the drawings which disclose: Figure 1 discloses a small fork-lift truck according to one aspect of the disclosure.

Figure 1a discloses a small fork-lift truck according to a second aspect of the disclosure.

Figure 1b discloses a small fork-lift truck according to a third aspect of the disclosure.

Figure 2 discloses a large fork-lift truck according to one aspect of the disclosure.

Figure 2a discloses a large fork-lift truck according to a second aspect of the disclosure.

Figure 2b discloses a large fork-lift truck according to a third aspect of the disclosure.

Figure 3 discloses in general terms the detection, in particular according to the aspect according to figure 1 and 2.

Figure 3a discloses in general terms the detection, in particular according to the aspect according to figure 1a, and 2a.

Figure 3b discloses in general terms the detection, in particular according to the aspect according to figure 1b, and 2b.

Figure 4 discloses the load features that are detected according to an aspect of the disclosure in accordance with any general measurement, in particular referring to figure 1 and 2.

Figure 4a discloses in general terms the detection, in particular according to the aspect according to figure 1a and 2a.

Figure 4b discloses in general terms the detection, in particular according to the aspect according to figure 1b and 2b.

Figure 5 discloses a main control unit in general terms of any size of model of fork-lift truck according to one aspect of the disclosure.

Figure 6 discloses a flow chart of a method of operating a fork-lift truck according to an aspect of the disclosure.

DETAILED DESCRIPTION The present disclosure relates to a fork-lift truck in general. The definition of a fork-lift truck according to the present disclosure is that it should have a load carrier that can engage a pallet for engaging a load. A vehicle that can engage a load but cannot engage a pallet is not to be comprised in the present disclosure. The load carrier of the fork-lift truck of the present invention preferably comprises two forward extending forks. However it is thinkable with other configurations such as one, three or four forward extending forks. The model of the fork-lift truck is not relevant for the present disclosure. The fork-lift truck can be a low lifting fork-lift truck, a stacker fork-lift truck, a very narrow isle fork-lift truck, a combi fork-lift truck, a reach fork-lift truck, a simple pallet truck, any tiller arm truck and any rider truck.

Figure 1 discloses a low lifting fork-lift truck 1, such as a tiller truck. The fork lift truck 1 has a load carrier 2. The load-carrier can be exemplified by a first 11 and a second fork 12. The load carrier has an outer end 7 and an inner end 6. The inner end 6 of the load carrier is closer to the body 14 of the fork-lift truck 1. The fork-lift truck 1 is provided with a first detecting device 10a. The fork-lift truck is further provided with a control aid device 8, 9. The control aid device can be a sound device 8. The control aid device can be a display device 9. The control aid device can be both a sound device 8 and a display device 9. The fork-lift truck 1 also is provided with a load carrier control device 13, for controlling the load carrier 2, such as hydraulics etc. Further the fork-lift truck is also provided with a load carrier control unit 5. The fork-lift truck is preferably also provided with a main control unit 20.

Figure la discloses a low lifting fork-lift truck 1 according to a further aspect. The fork-lift truck in figure la has all features in common with the aspect according to figure 1. The only difference is that the fork-lift truck 1, of figure la is provided with a second detecting device 10b. The second detecting device 10b is according to figure la positioned on different load carrier element 12, fork, than the first detecting device 10a. The configuration is best seen in figure 3a.

Figure 1b discloses a low lifting fork-lift truck 1 according to a further aspect. The fork-lift truck in figure 1b has all features in common with the aspect according to figure 1. The only difference is that the fork-lift truck 1, of figure 1b is provided with a second detecting device 10b. The second detecting device 10b is according to figure 1b positioned on the same load carrier element 12, fork, as the first detecting device 10a. The configuration is best seen in figure 3b.

Figure 2 discloses a reach fork-lift truck 1. The common features of the low lifting fork-lift truck of figure 1 have been denominated with the same numbers. I.e. load carrier 2, exemplified first 11 and second fork 12, outer end 7, inner end 6, body 14, first detecting device 10a, control aid device 8, 9, sound device 8, display device 9, load carrier control device 13, load carrier control unit 5, preferred main control unit 20. The main difference between the fork-lift truck 1 of figure 1 and fork-lift 1 of figure 2 is the mast 15, on which the load carrier 2 are movable for lifting loads to higher levels. The mast 15 of figure 2 can also be fitted to the low-lifter fork-lift truck of Figure 1.

Figure 2a discloses a reach fork-lift truck 1. The difference between the reach fork-lift truck 1 of figure 2 and the fork-lift truck 1 of figure 2a is that the fork-lift truck 1 of figure 2a further comprises a second detecting device 10b. The second detecting device 10b is according to figure la positioned on different load carrier element 12, fork, than the first detecting device 10a. The configuration is best seen in figure 3a.

Figure 1 and Figure 2 discloses a first aspect of the present disclosure where the first detecting device 10a provided on a first 11 fork of a load carrier. This is further explained in relation to Figure 3, where the position of the first detection device 10a is clearly visualized. Of course the position of the respective detecting device 10a, the fork 11, is only exemplified. It is possible to position the detecting device 10a at different positions on respective fork 11 or 12. The difference in signal can then be handled by the load carrier control unit 5. The exemplified drawing of Figure 4discloses a measurement of the same load feature 4a. Flowever it is of course possible to rotate the detecting device 10a such that it can detect the second load feature 4b instead of detecting the load feature 4a.

Figure la and Figure 2a discloses a second aspect of the present disclosure where the first detecting device 10a and the second detecting device 10b are provided on a first 11 and a second 12 extending fork of a load carrier. This is further explained in relation to Figure 3a, where the position of the first detection device 10a and the second detecting device 10b is clearly visualized. Of course the position of the respective detecting device 10a, 10b on each fork 11, 12 are only exemplified. It is possible to position the respective detecting device 10a, 10b at different positions on the respective fork 11, 12. As an example of this the first detecting device 10a, can be positioned closer to the body 14 of the fork-lift truck 1 than the second detecting device 10b. The difference in signal can then be handled by the load carrier control unit 5. The exemplified drawing of Figure 4a discloses a measurement of the load feature 4a and load feature 4b. The advantage of positioning the detecting devices 10a, 10b on a respective fork 11, 12 is that the resolution in transversal direction is increased. Thus the relative position in transversal is easier to determine more exact, than when the detecting devices are positioned on the same fork. It is also an advantage that if one fork is damaged by an operator the detecting device of the other fork will still be fully functional.

Figure 1b and Figure 2b discloses a third aspect of the present disclosure where the first detecting device 10a and the second detecting device 10b are provided on the same extending fork of a load carrier. This is further explained in relation to Figure 3b, where the position of the first detection device 10a and the second detecting device 10b is clearly visualized. Of course the positions of the respective detecting device 10a, 10b on the fork 11 are only exemplified. A common wiring can be used along the fork 11 and be divided close to the detecting devices 10a, 10b. It is possible to position the respective detecting device 10a, 10b at different positions along the fork. As an example of this the first detecting device 10a, can be positioned closer to the body 14 of the fork-lift truck 1 than the second detecting device 10b. The difference in signal can then be handled by the load carrier control unit 5. The exemplified drawing of Figure 4b discloses a measurement of the same load feature exemplified as load feature 4a.

The function of the fork-lift truck 1 according to any of the aspects above will now be explained in a general manner by discussing a single detecting device. The operation of the fork-lift truck in general, requires approaching of the load carriers 2 to a load 4. The detecting device 10a, 10b sends out a signal. The signal rebounds on the desired load feature 4a or 4b and returns an echo signal that is detected by the detecting device 10a, 10b. An output data is then transmitted to a load carrier control unit 5, figure 5. The output data is based on the echo signal. Depending on where the load carrier is positioned in front of the load features, the echo signal is present or not. The output data is used by the load carrier control unit 5, to determine a relative position of the load carrier 2 in relation to the desired load feature 4a, 4b. The relative position is only determined as a point 26 on a plane 25 that is defined as extending in a perpendicular direction to the central axis 4c, 4d of the load feature 4a, 4b. In particular the plane is defined to tangent the end side 27 of a load or pallet comprising the load features 4a, 4b. The load carrier control unit 5 then provide a control output, based on the determined relative position to a control aid device 8, 9. Thus by monitoring the different echo signals the load carrier control unit 5 can determine a specific control signal to be sent to the control aid device 8,9. In particular it is advantageous that the system and assessment of the relative position is based on the following. In the aspect according to figure 3b and 4b there are two detecting devices 10a and 10b and the determination of the relative position functions as follows: An echo signal from the first detecting device 10a combined with no echo signal from detecting device 10b, the relative position is determined by the load carrier control unit 5 as to be that the load carrier is too far to the left. Echo signal from detecting device 10b and not from detecting device 10a, the relative position is determined as to be that the load carrier is too far to the right. No signal from any of the detecting devices 10a or 10b, the load carrier is positioned in right position for engaging the load/pallet. In view of figure 3a and 4a, the functioning is essentially the same. I.e. as seen in figure 4a the echo signal from the detecting device 10a is present but not from detecting device 10b, thus the load carrier is too far to the left. The need for the operator to assess the situation is always present and the system requires an operator to manoeuvre the load carriers to the vicinity of the load features 4a, 4b in order to achieve the advantage of being guided to the correct position for the load carriers. If the load carrier is for example so far to the side that only one fork of a load carrier can engage correctly a pallet, and the other fork is completely outside the pallet/load, the system will not operate correctly. For the system according to figure 3 and 4 the following applies, the operator gets indication of the relative position not being the correct position for engaging the load, if an echo signal is received, that is when the load carrier 2 is not in the correct position for engaging a pallet or a load. However he will get less functionality as the system according to the aspect of figure 3 and 4 only indicates that he should move the load carrier to the right. If the load carrier gives an echo signal when it is too far to the right, the operator will need to assess this situation manually. For all aspects it is also possible to assess the relative position in vertical direction in the same manner.

The detecting device 10a or devices 10a, 10b in any of the disclosed aspects above is preferably ultrasonic sensors. The detecting devices 10a, 10b can also be laser sensors that send out a laser signal from which a laser signal echo can be detected. Other type of sensors is thinkable, such as radar type sensors.

In a further general discussion in referring to figure 3, 3a, 3b and Figure 4, 4a, 4b the load features 4a and 4b to be detected are disclosed. The load features is preferably the boundary 4a, 4b of the openings 44a, 44b where the load carrier 2 is intended to be inserted when the load 4 is to be moved, that is the opening boundary 4a, 4b, is actually detected. In the figures 3, 3a, 3b and 4, 4a, 4b, the load features 4a, 4b, are disclosed as the boundaries of the tunnels where the load carrier 2 can be inserted. As an example referring to figure 3a and 4a, the detecting areas 16a, 16b of the first 10a and second detecting devices 10b are disclosed, the detecting areas 16a, 16b are detecting the vertical left or right border of the load features 4a and/or 4b. It is of course intended that the monitoring areas 16a, 16b is not restricted to one side of the load features 4a, 4b. Both the upper border and the combination of the left and right border can be detected, in any combination. Other features of the pallet can be used instead of the opening boundaries 4a, 4b. The corner as well as the middle block of the pallet is thinkable as a load feature also to be used, together or instead of the boundaries of the openings 4a, 4b.

In general for all the aspects discussed above the load carrier control unit 5 is arranged such that it can receive and process the output data that come from the detecting devices 10a and/or the detecting device 10b. Preferably the load carrier control unit 5 comprises a processor unit and a memory unit. The control unit 5 is programmed with a computer readable code that when executed will perform the discussed determination of the relative position of the load carriers, in the said plane 25. The control output is sent to the control aid device 8, 9. The load carrier control unit 5 is programmed such that it can alter the control output with regard to the signal received from the detecting devices 10a, 10b, depending on the determined relative position between the load carrier 2 and the load features 4a, 4b. According to one aspect of the disclosure the carrier control unit 5 is integrated into a main control unit 20 of the fork-lift truck 1, see figure 6. Thus no new hardware is need for the carrier control unit 5. The carrier control unit 5 is thus software that is integrated in the existing hardware of the main control unit 20 of the fork-lift truck. The main control unit 20 of the fork-lift truck 1 can also be named the truck computer. According to another aspect of the disclosure the load carrier control unit 5 is a separate hardware. This allows for a choice of position of the load carrier control unit 5 that is more free and also it allows for easy service of the load carrier control unit 5 should it fail.

Control aid device 8 comprises preferably a sound device that can send out sound detectable by an operator. The control aid device 8 thus comprises a speaker or an ear phone. The speaker is operable with the control output sent from the load carrier control unit 5 such that a different sound is achieved when the control output is changed by the load carrier control unit 5. In a preferred aspect the output from the sound device 8 set to null when the determined relative position is such that the point 26 falls within the inner area of the detected load feature 4a and/or load feature 4b. In a preferred disclosure the control aid device 8 is only a sound device 8. The control aid device can also however comprise a display device 9. The display device 9 can display the relative position of the load carrier 2 in relation to the load features 4a, 4b. The display device 9 can be the only control aid device of the fork-lift truck 1. The display device 9 can also be installed together with the sound device 8, such that the relative position of the load carrier 2 is both displayed visually and also detectable via the sound device 8. The load carrier control unit 5 can send out both a control output to a first control aid device 8 and a second control aid device 9.

In a further aspect having all features of the control aid device 8 above, there is provided several sound devices. The sound devices 8 are preferably positioned on both sides of the operator of the operator when manoeuvring the fork-lift truck 1. Thus the load carrier control unit 5 is operable to send out a control out put that gives a sound that comes from a predetermined side of the operator corresponding to the side on which the load carrier 2 is positioned when the predetermined position is determined. There can be further sound devices in a position higher up above the operator for giving an output corresponding to the height of a point 26 above the upper boundary of a respective load feature 4a and/or 4b. This is preferably conceived in a fork-lift truck 1, according to figure 2, 2a, 2b. However it can also be achieved on a fork-lift truck 1 according to figure 1, 1a, 1b by positioning the sound device on a rod that extends above the operator.

With regard to the positioning of the detecting devices in general, the advantage of positioning the detecting devices closer to the outer end 7 of the load carrier 2 is that the distance between the detecting devices 10a, 10b and the load features 4a, 4b are minimized. Thus the resolution of the detected echo signal of is optimized. The resolution will increase the closer the detecting device 10a, 10b is positioned with regard to the load features 4a, 4b.

By modifying an existing fork-lift truck the above discussed different aspects of a fork-lift truck 1 can be achieved. Such a modifying should comprise to install one detecting device 10a or two detecting devices 10a and 10b according to any of the aspects above. And further to also provide a load carrier control unit 5 according to any of the aspects above and further provide a control aid device 8, 9 according to any of the aspects above.

The present disclosure also relates to a method of operating a fork-lift truck 1 according to any of the aspects above. The method is disclosed in Figure 6. The method comprises the steps S1-S8: 51. providing a fork-lift truck comprising a load carrier provided with at least one detecting device and providing a load comprising at least one load feature, 52. approaching the load with the load carrier of the fork-lift truck, 53. sending out a signal from the detecting device and, 54. receiving an echo signal from the at least one load feature by the detecting device, 55. sending an output data based on the received echo signal to a load carrier control unit, 56. determining the relative position of the load carrier with regard to the load feature, by the load carrier control unit, based on the received data, wherein the determined relative position corresponds to a point on a plane that is defined as extending in a perpendicular direction to the central axis of the load feature, 57. providing a control output from the load carrier control unit to a control aid device of the fork-lift truck based on the relative position detected, 58. adjusting the relative position of the load carriers based on an output from the control aid device.

The method is particularly favourable as it improves the ergonomics. The steps are performed in consecutive order.

Step S1 can either be provided by manufacturing a new fork-lift truck 1, or by modifying an existing fork-lift truck 1.

Step S2 is preferably performed manually by an operator. This is in most cases performed by manoeuvring the whole fork lift truck 1. But S2 can also be performed by moving the load carriers 2 in relation to the fork-lift truck 1.

Step S3 is performed as described above, i.e. by sending out a signal from the detecting devices Step S4 is performed by receiving an echo signal, Step S5 the load carrier control unit sends an output data based on the echo signal to a load carrier control unit.

In step 6 the carrier control unit 5 determines the relative position of the load carrier with regard to the load feature based on the received data, this is only made in a manner such that a point in a plane is determined.

In step 7 the control output is transferred to the suitable control aid device, which can be a sound device, a display device, or both, based on the relative position detected.

In step 8, the operator manually alters the position of the load carrier, based on the output given.

Other steps can be added such as: S3a determining the height of the load by moving the load carriers to a height position where the load no longer gives an echo signal.

S3b determining the width of a load by moving the load carrier sideways such that the outer borders of the load can be determined.

Claims (9)

1. CLAIMS 1. Fork-lift truck (1) comprising, a load carrier (2) and a load carrier control unit (5), a control aid device (8,9), wherein the load carrier (2) is provided with at least one detecting device (10a), wherein the detecting device (10a) is arranged to be able to send out a signal and receive an echo signal from a first load feature (4a), wherein the detecting device (10a) is arranged to be able to send an output data based on the received echo signal, to the load carrier control unit (5), wherein the load carrier control unit (5) is arranged to be able to, based on the received data, determine a relative position of the load carrier (2) in relation to the first load feature (4a) and to provide a control output, based on the determined relative position, to the control aid device (8, 9), wherein the determined relative position corresponds to a point (26) on a plane (25) that is defined as extending in a perpendicular direction to the central axis (4c) of the first load feature (4a), wherein the load feature (4a, 4b) is the boundary of a pallet opening (44a, 44b) intended to receive the load carrier (2), wherein the load carrier (2) has two forks (11, 12), characterized in that, the detecting device (10a) is positioned on one of the forks (11), preferably closer to the outer end (7) of said fork (11), wherein the control aid device (8, 9) comprises a sound device (8), wherein said sound device (8) is operable with the load carrier control unit (5), for giving a sound output that is detectable by an operator, based on the control output from the load carrier control unit (5), wherein the sound output is arranged to be different with regard to at least two different predetermined relative positions, such that a specific relative position of the load-carrier (2) is detectable by an operator, wherein there is provided several sound devices, the sound devices (8) are positioned on both sides of the operator when manoeuvring the fork-lift truck (1), thus the load carrier control unit (5) is operable to send out a control out put that gives a sound that comes from a predetermined side of the operator corresponding to the side on which the load carrier (2) is positioned when the predetermined position is determined.

2. Fork-lift truck (1) according to any of the claims above, wherein the control aid device (8, 9) comprises a display device (9), wherein the display device (9) is operable with the load carrier control unit (5), for giving a an output to the display device (9), that is detectable by an operator, based on the control output from the load carrier control unit (5), preferably the display device (9) is located at/or within the operators position at operation of the fork-lift truck (1).

3. Fork-Lift truck (1) according to any of the claims above, wherein the load carrier control unit (5) is comprised within a main control unit (20) of the fork-lift truck (1).

4. Fork-lift truck (1) according to any of the claims above, wherein the said plane (25) is defined to tangent the end side (27) of a load pallet comprising said first load feature (4a).

5. Fork-lift truck (1) according to any of the claims 1-4, wherein the load carrier (2) comprises a second detecting device (10b), that is positioned in transversal direction of the first detecting device (10a) on said load carrier (2), wherein the second detecting device (10b) is arranged to be able to send out a signal and receive an echo signal from a first load feature (4a) or a second load feature (4b), wherein the second detecting device (10b) is arranged to be able to send an output data based on the received echo signal, to the load carrier control unit (5), wherein the load carrier control unit (5) is arranged to be able to, based on the received data, determine a relative position of the load carrier (2) in relation to the first load feature (4a) and/or the second load feature (4b)and to provide a control output, based on the determined relative position, to the control aid device (8, 9) wherein the determined relative position corresponds to a point (26) on a plane (25) that is defined as extending in a perpendicular direction to the central axis (4c) of the second load feature (4b).

6. Fork-lift truck (1) according to claim 5, wherein the load carrier control unit (5) is arranged to make a calculation based on both the outputs received from the first detecting device (10a) and the second detecting device (10b), for a more precise determination of the relative position of the load carrier (2) in relation to the load feature (4a) and/or load feature (4b).

7. Fork-lift truck (1) according to any of the claims 1-6, wherein the detecting device (10a) is an ultrasonic sensor or the detecting devices (10a, 10b) are ultrasonic sensors or wherein the detecting device (10a) is a laser sensor or the detecting devices (10a, 10b) are laser sensors.

8. Fork-lift truck (1) according to any of the claims 1 and 5, wherein the first and the second detecting devices (10a, 10b) are positioned on the same fork (11), or wherein the first and the second detecting devices (10a, 10b) are positioned on separate forks (11, 12).

9. Method for operating a fork-lift truck according to any of the claims 1-8, comprising the steps of: 51. providing a fork-lift truck (1) comprising a load carrier (2) provided with at least one detecting device (10a) and providing a load (4) comprising at least one load feature (4a), 52. approaching the load (4) with the load carrier (2) of the fork-lift truck (1), 53. sending out a signal from the detecting device (10a) and, 54. receiving an echo signal from the at least one load feature (4a) by the detecting device (10a), 55. sending an output data based on the received echo signal to a load carrier control unit (5), 56. determining the relative position of the load carrier (2) with regard to the load feature (4a), by the load carrier control unit (5), based on the received data, wherein the determined relative position corresponds to a point (26) on a plane (25) that is defined as extending in a perpendicular direction to the central axis (4c) of the load feature (4a), 57. providing a control output from the load carrier control unit (5) to a control aid device (8, 9) based on the relative position detected, 58. adjusting the relative position of the load carriers (2) based on an output from the control aid device (8, 9).