GB2437629A

GB2437629A - Display for assisting lift truck operator

Info

Publication number: GB2437629A
Application number: GB0707822A
Authority: GB
Inventors: Jyri Mr Vaherto
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-25
Filing date: 2007-04-24
Publication date: 2007-10-31
Anticipated expiration: 2027-04-24
Also published as: GB0707822D0; FI20065684A0; GB2437629B; FI20065684A; FI124747B; DE202007005697U1

Abstract

A method for assisting a lift truck operator, in which loads are handled with a lift truck comprising load-grappling devices (106). Parameters related to handling of loads are measured (12) obtaining thus measurands. Limit values corresponding to the measurands are entered into a system (32). At least one of the measurands is compared (16) to the set limit values corresponding to the parameter. As a result of the comparison, the deviation (22) between the measurand and the limit value is obtained. In addition, at least one deviation (22) is displayed to the operator graphically steplessly. The invention also relates to a corresponding system.

Description

iETHOD AND SYSTEM FOR ASSISTING A LIFT TRUCK OPERATOR The invention

relates to a method for assisting a lift truck operator, in which loads are handled with a lift truck comprising load-grappling devices, and parameters related to handling of loads are measured obtaining thereby measurands, and limit values corresponding to the measurands are entered into a system, and at least one of the measurands is compared to the set limit values corresponding to the parameter, and the deviation between the measurand and the limit value is obtained as the result of this comparison. The invention also relates to a corresponding system.

While using a lift truck, the lift truck operator controls the lift truck and the load present in the lift truck forks based on what he sees. It is known that the possibility for the operator to see the load is a problem. Therefore the operator may need to work in physically poor positions in order to make observations of the load. Equipment are known in prior art in which the operator is assisted in controlling the load more accurately. Of such equipment, reference is made here to the equipment disclosed in US patent No. 5011358, in which the angle of the lift truck forks is measured. The measuring results obtained, i.e. the measurands, are compared to a limit value. A limit value may be for example the verticality of the mast. This system provides the operator with information based on which the operator can control the correct angle of the mast relative to the load handling. However, in the equipment according to US patent No. 5011358, the limited indication capability of the display is a problem, since while the items to be indicated vary, the display remains the same.

GE 2360500 discloses a system in which the angle of tilt of the forks is displayed. However, the angle of tilt is displayed as such, which makes it difficult to achieve the desired angle of tilt. DE 10115093, in turn, discloses a system in which arm levels and angles are displayed. The indication is, however, very rough, which means that the operator cannot control the load very accurately based on this. ED 1604942 discloses a system for showing a video image for a lift truck operator.

In prior art arrangements, LEDs or similar have been used to indicate that a certain level is being approached, with each LED indicating an external distance (a step) eg 5 to 20 cm, resulting in a low accuracy.

The object of the invention is to provide a method by which the lift truck operator is assisted in handling loads more accurately than heretofore. The characteristic features of this invention become evident from the appended claim 1.

Another object of the invention is to provide a system with which the difference between the measuring result and the set point of the control parameter is indicated to the operator more clearly than heretofore. The characteristic features of this invention become evident from the appended claim 9. In the invention, the difference between the measurement data and the limit value is displayed to the operator steplessly visually, whereupon the operator can control the load more accurately based on the information received from the display.

The term steplessly in this specification means substantially continuously. That is, substantially any value within the operating range can be displayed (subject to the resolution of the graphical display) not just the discrete values of the

prior art.

The lift truck operator is assisted in load handling by a method in which loads are handled with a lift truck. The lift truck comprises load-grappling devices for handling the loads.

Parameters related to handling of loads are measured obtaining thus measurands. Limit values corresponding to the measurands are entered into the system. At least one of the measurands is compared to the set limit values corresponding to the parameter. As the result of this comparison, the deviation between the measurand and the limit value is obtained. In addition, at least one deviation is displayed to the operator steplessly graphically. Graphic visualization can be implemented using a projector or a display. When using a projector, the graphic view can be projected to the windscreen of a lift truck, for example. In prior art the visualization has been very stepwise, since the operator has been able to see only if the angle of the lift truck mast and thus that of the load is below, above or exactly at the set point. Even the stepless visualization includes the steps caused by the pixels of the display. However, as the steps set by the pixels are very small, they have no practical relevance. Stepless visualization means that the visualization is stepless as regards the use, although small steps would be technically present. The operator sees for instance the angle for a steplessly displayed deviation. Besides the angle, other parameters can be indicated to the operator, such as the position of the fork under the load. This is important, since the arm tips of the lift truck fork must be precisely at the desired depth under the load during load handling. Being able to control the load more than before based on the displayed deviation, the operator does not need to monitor the load in awkward positions, and the work ergonomy improves remarkably.

In addition, the work is performed more accurately than before when the operator knows precisely the position of the lift truck load-grappling devices and thus that of the load.

In one embodiment, at least two of the limit values are vertical position limit values of the load-grappling devices.

In contrast, as regards the measurands, at least one is the vertical position measurand of the load-grappling devices. The vertical position measurand of the load-grappling devices is compared to at least two set vertical position limit values of the load-grappling devices. In this way at least two vertical position deviations are obtained. These at least two vertical position deviations are indicated to the operator simultaneously steplessly graphically. When two vertical position deviations relative to the same vertical position measurand are simultaneously indicated to the operator, the operator can move the load at a very high accuracy. Thus the operator can observe the position of the load-grappling devices simultaneously with respect to two critical values.

This enables avoiding many collisions in precise operating conditions.

In another embodiment the vertical position deviations are a first vertical position deviation and a second vertical position deviation. Cf these the first vertical position deviation indicates the state of the load-grappling devices at the approaching height. In contrast, the second vertical position deviation indicates the state of the load-grappling devices at the handling height. The term approaching height' refers to the height at which the load-grappling devices can be taken to the vicinity of the load without touching the load or the shelf location. Similarly, at this height the load-grappling devices can be removed from the vicinity of the load after the handling operation without causing damage. The term handling height', in turn, refers to the height at which the load is supported by the load-grappling devices. That is, at the approaching height the load-grappling devices, such as arms, can be set at the free lifting points of the lift truck platform located under the load without touching the]çoad or its surrounding. At the handling height, in contrast, the load-grappling devices, such as arms, have been lifted such that the load is supported by them. On the other hand, when at the handling height the load does not contact for example the above located shelf, even from above. Thus at the handling height the load can be freely removed from the storage location, such as a shelf. In this embodiment two vertical position deviations indicated simultaneously graphically steplessly enable notably better information than before for the lift truck operator. Then the lift truck operator does not need to continuously reach out from the lift truck to see the position of the forks. The operator can control the load-grappling devices to a desired location by monitoring the graphic display. When the parameters are shown to the operator simultaneously, it is evident if the load is currently being handled or if the load-grappling devices can be freely moved.

In a third embodiment loads are positioned in shelf locations and the shelf locations have certain shelf heights. In addition, vertical position limit values of the load-grappling devices are computed based on the shelf heights. In this way the load can be accurately controlled relative to the shelves.

In a fourth embodiment at least one parameter is automatically controlled based on the deviation. In other words, the load is automatically controlled based on the deviation. Thus the load is controlled independently of the operator. Then the system itself controls the load based on the measurands and limit values. When the control is based on measurands and limit values, it is based on deviations, although the system would not have been programmed to compute an actual deviation.

In a fifth embodiment the deviation is indicated to the operator at different times in different views. These different views include different pieces of information, or the positioning of the information is different between the displays. Thus it is possible to show the most central information in the display for assisting the operator at each particular moment. In other words, the lift truck operator has many different tasks during the day, which further consist of a varying combination of work stages. The mere positioning of a load onto a shelf consists of several different work stages the aspects to be considered in each of which are different.

When picking the load the operator must know precisely how far the forks have been pushed under the load. After this the operator lifts the load to a suitable transport height. When moving the load, the operator must pay attention to the boom position. When lifting the load onto a shelf the operator must know the position of the load and the location of the shelves.

When the information displayed can he selected suitably for each work stage, the work proceeds smoothly.

In a sixth embodiment the view displayed is automatically selected based on the measurands. Automatic selection' refers to a selection in which the selection is made without a separate command given by the operator. Various conditions can be used for selecting automatically the view based on the measurands. A simple condition can be that the changing measurand is displayed highlighted compared to those that remain fixed.

In a seventh embodiment there are several limit values at least per one measurand, since the same parameter must be accurately controlled at different times to several values.

Advantageously the measurand is compared to the closest limit value. When the closest limit value set is automatically selected as the reference point for the measurand, the operator can observe how the measurand is compared first to other limit values, and finally, while the operator is still moving the load, the measurand is compared to the limit value related to the load handled. This function enables entering simultaneously many limit values to the system.

The invention is described below in detail by making reference to Lhe enclosed drawings, which illustrate some of the embodiments of the invention, in which Figure 1 shows the system according to the invention, Figure 2 is a view of the system according to the invention, in which information is displayed as numerical values and graphically, Figure 3 is a view of the system according to the invention, in which the measurands are presented mainly as numerical values, Figure 4 shows the main menu of the system according to the invention, Figure 5 shows the "Select View" submenu of the system according to the invention, Figure 6 shows an operating condition of a lift truck which can be avoided by the system according to the invention, and Figure 7 shows an operating condition of the system according to the invention, in which the lift truck is used to handle loads stored in a shelving.

Figure 1 shows a system 10 partially according to the invention for assisting a lift truck operator in load handling. The system comprises load-grappling devices, sensors 12, limit value setting means 14, and comparison means 16. The load-grappling devices are used to grab the loads for handling the loads. The sensors 12 are used to measure parameters related to load handling and to create measurands. The limit value setting means 14 are used to set limit values. Setting of limit values can also be performed via a computer, which allows an easy programming of even a large number of limit values at once. This type of embodiment can be used in storages comprising a large number of different shelvings. The comparison means 16, in turn, are used to compare the measurands and limit values for creating a deviation 22. The comparison means 16 are located in a central unit 32. When comparing the measurands and the corresponding limit values, deviations are created. In addition, the system includes a display 18 for indicating steplessly graphically at least one deviation 22. The deviation can also be indirectly indicated in the display by indicating the measurand and the limit value, in which case the operator will see the deviation. It is essential that the graphic display shows the deviation indirectly or directly so as to allow the operator to know the position of the load precisely by monitoring the view 20 shown in the display 18. The operator can lift the load at a higher speed than in prior art when he knows that the distance left to the desired height, i.e. the set limit value, is still remarkable. The operator can see, based on the steplessly displayed deviation 22, when the load approaches the desired shelf height, which permits the operator to reduce the lifting speed and to prepare for stopping the load at the desired height. Being able to control the load more than before based on the displayed deviation, the operator does not need to observe the load in awkward positions, and the work ergonomy improves remarkably. In addition, load handling becomes more reliable and damage caused to the loads reduces remarkably. A system according to the invention can also be utilized in other work machines, such as wheel loaders.

The system 10 according to the invention shown in Figure 1 facilitates lift truck handling. Several sensors can be connected to the system as required. Sensors 12 have been connected to the central unit 32. Sensors 12 included in the system 10 can include an angle sensor 24, horizontal position sensor 26, vertical position sensor or height position sensor 28, and compression pressure sensor 30. The sensors to be used are selected from these as required. It is self-evident that a lift truck with arms does not require a compression pressure sensor. Additional sensors can be included when required, if another sensor essential for load handling appears. Such a sensor could be for example a load weight measuring sensor.

The system 10 according to the invention shown in Figure 1 comprises control means 34. The control means are used for controlling the system. As part of the system usage, these can be used to set limit values in which case they function partly as setting means 14. In the embodiment shown in Figure 1 the control means 34 include five buttons 36 -44, namely: button E 36, button C 38, Up arrow 40 and Down arrow 42. Button E accesses the main menu when the display is in the basic mode.

Within a menu, button E can be used to confirm a desired function or a value entered. Button C accesses the menu mode when the display is in the basic mode. When in the menu mode, button C returns to a previous menu level. In addition, button C can be used to cancel a previous entry. When the display is in the basic mode, the arrow buttons can be used in the visual view to select directly some of the most important settings.

The control means also include an acoustic signal button 44, which can be used to activate and deactivate the equipment's acoustic signals. Advantageously the system is switched on automatically when the lift truck is started. Thus the system is always on during the use of the lift truck, ensuring that the system does not remain unused even in short, easy, or routine tasks.

A liquid crystal display can be used for the visual indication. A display performs better in various lighting conditions compared to a projector implementation. In case of a liquid crystal display, there is a great freedom for locating it. The lightness of the liquid crystal display contributes to this free positioning.

The display 18 shown in Figure 1 is a liquid crystal display 19 including 8.192 pixels and two colors. Generally, the display has 5.000 -50.000, preferably 8.000 -30.000 pixels.

In the display shown in the figure the number of the vertical pixels is 64 and that of the horizontal pixels is 128. The display could be notably larger or even more accurate, and it could include 128 * 252 = 32.256 pixels, for example. The display used can also be a color display. Using a color display is advantageous as it allows utilizing the possibilities provided by the colors for attracting the attention of the operator, i.e. in illustration. Green can be used, for example, for coloring the mast when it is in the angle indicated by the limit value. On the other hand, the background color of the display can be changed red, if the system detects that the operator is handling the load erroneously, by pressing too hard, for example.

The display shown in Figure 1 is a liquid crystal display. The liquid crystal display is light and thus it offers freedom in positioning. The display shown in the figure is graphic, but a text-based display could also be used in the system. In this case, a text-based display would show the deviation steplessly. However, the display to be advantageously used is graphic, since a graphic display enables a more versatile utilization of pixels. For example, scaling can be performed steplessly, when the pixels can be switched on and off as desired independent of each other.

The central unit can be integrated to the display or it can be separately located further away from the display.

Advantageously the central unit is, however, separated from the display. When the central unit is separated, the sensor cables do not come directly to the display. Thus the display and the control means are conveniently visible and unnoticeably connected further to the separately located central unit. Locating the central unit separately is useful particularly when the central unit contains the control means for controlling automatically at least one parameter, because the control means, when located in the central unit, increase the size of the central unit remarkably.

The display 18 of the system 10 according to the invention shown in Figure 1 is adapted to show various views 20 at different times. These different views include different pieces of information, or the positioning of the information is different between the displays. The operator can select for display in the user interface the most central information relative to each work stage. Figures 2 and 3 illustrate views of the display 18 of the system according to the invention.

The number of various views for displaying the information for assisting the operator is at least 6, advantageously 10. In practice, the number of views can be extremely high, as a view can show one measuring parameter or different combinations of measuring parameters. The information can be displayed graphically, as numerical values, or as combinations thereof.

A graphic view displays the information for the driver graphically by means of control bars or similar. When the information is indicated as numerical values, only the numerical values are shown of these. A display using combinations of a graphic indication and numerical values is more illustrative than those mentioned above.

At least one of the views shown in the display depicts the mast angle or the vertical position of the load-grappling devices connected to the mast. The display views can vary a lot, but since controlling the mast angle is very central in the lift truck operation, at least one of the views indicates the mast angle of the lift truck. When handling loads it is very essential to know precisely their vertical position, therefore, at least one view shows the vertical position of the load-grappling devices attached to the mast. The vertical position of the load-grappling devices is directly connected to the vertical position of the load handled.

When the number of measuring parameters is three, and these are graphically shown in the display, the number of different combinations or views will be 7. Correspondingly, the number of different views showing only numerical values will be 7 when the number of measuring parameters is three. As regards the use of the system, it is advantageous that a portion of the information is indicated graphically and a portion as numerical values. The number of such combinations amounts to dozens of combinations when the number of measuring parameters is 3. If considering also the degree of highlighting for the measuring parameter within the view, the number of views still increases. In other words, even the same information can be indicated in the display highlighted in a different way, which increases the number of different views. As regards usability, it is central that measurands irrelevant to the operator can remain unshown and only the most central parameters are monitored. It may be that a particular work stage has only one central parameter. A system according to the invention, in which one and the same display can show a multitude of different views, enables implementation of a system that assists the operator efficiently. Since the display must not be too large to be able to locate it in the lift truck as desired, the views must be varying so that the most central aspects can always be indicated to the operator.

Figure 2 shows a view of the system 10 according to the invention, in which information is displayed as numerical values and graphically. The figure shows the angle, the position of the arms under the load, and the vertical position.

The system 10 according to the invention shown in Figure 1 additionally comprises led lights for indicating central information. Such led lights incorporated in the display are advantageous as the operator may have become acquainted with corresponding elements in connection with earlier control systems. Therefore, in connection with an informative display, it may be useful to show a portion of the information in a much reduced form, in a customary way.

In the view 20 of the system according to the invention shown in Figure 2, the angle is displayed by an indicator bar 46 for the angle deviation at the top of the view 20. The indicator bar 46 for the angle deviation is located in such a way that the zero point 47 is directly above the mast 49 shown in the display. When the lift truck mast is tilted backwards, the indicator 45 in the angle deviation indicator bar 46 is on the left of the mast 49 shown in the view. In contrast, when the lift truck mast is tilted forwards, the indicator in the angle deviation indicator bar is on the right of the mast shown in the view. The defined angle limit value 48 is shown in degrees. When the lift truck mast is at the set limit value, the limit value reached is flashing. In addition, when the mast is in the fully vertical position, the tip of the mast flickers. The angle display area 62 reveals the scale within which the angle deviation indicator bar 46 is set at each moment. Indication 5 means that when the angle deviation indicator bar 46 is completely filled until to the right edge, the lift truck mast is tilted by 5 . The angle deviation indicator bar 46 can be scalable, in which case it displays a wider area for showing the mast angle, if required. The actual tilt angle of the mast, i.e. the mast angle relative to the ground, is indicated as described above. When indicating the tilt angle relative to the ground, monitoring the tilt angle can be performed using acceleration sensors, for example.

In some special applications, the tilt angle of the mast is indicated relative to the lift truck. In this case the lift truck inclination relative to the ground is also measured using an acceleration sensor, for example, and when the tilt angle of the lift truck and mast relative to the ground is known, the mast angle relative to the lift truck is informed to the operator. The operator can also be provided information on the actual tilt angles of the lift truck and mast, as well as the angle between the lift truck and mast.

The view of the system according to the invention shown in Figure 2 depicts the position of the lift truck arms under the load in the indicator bar 50 for the horizontal position of the forks. More precisely, the control bar 50 shows the position of the arms relative to the set limit value. The indicator bar for the horizontal position of the forks changes from grey to black when the arms are correctly positioned under the load. The position of the tips under the load is shown with numbers 52 above the control bar 50. In contrast, below the control bar 50, the desired position of the tips under the load is indicated with numbers 54. The desired position of the tips under the load is the tip position limit value. More precisely, on both sides of the limit value there are areas within which the measured parameter is interpreted as limit value. Thus the limit value range could be for example 75 -85 cm. The limit value range could also he one-sided, in which case the limit value range could be for example 75 -80 cm. In this case, when it is desired that the arm tips are exactly flush with the rear edge of the lift truck platform, this number indicates the size of the lift truck platform.

In the system shown in Figure 1, at least one of the sensors 12 comprised in it is a vertical position sensor 28 for creating the vertical position measurand of the load-grappling devices. The limit value setting means 16 comprise height limit value setting means for setting at least two vertical position limit values. The comparison means are adapted to compare the vertical position measurand of the load-grappling devices at least with two vertical position limit values for creating a vertical position deviation. The display 18 is adapted to indicate simultaneously at least two vertical position deviations steplessly graphically. Thus the operator can observe the position of the load-grappling devices simultaneously with respect to two critical values.

The vertical position deviations are a first vertical position deviation and a second vertical position deviation. The first vertical position deviation is adapted to indicate the state of the load-grappling devices at the approaching height. The second vertical position deviation, in turn, is adapted to indicate the state of the load-grappling devices at the handling height. At the approaching height the load-grappling devices, such as arms, can be set at the free lifting points of the lift truck platform located under the load without touching the load or its surrounding. At the handling height, in turn, the load-grappling devices, such as arms, have been lifted such that the load is supported by them. The operation of such a system is illustrated in Figure 2.

In the view of the system according to the invention shown in Figure 2, the vertical position of the lift truck arms is shown with indicator bars56, 58 on the right of the mast 49.

When showing the vertical position of the arms, the position of the fork in the vertical direction relative to the set limit value is indicated. Shelf levels are typically used as limit values, since loads are typically lifted onto and from the shelves. More precisely, for each shelf level or shelf height, there are two vertical position limit values derived from the shelf levels. The first vertical position deviation is obtained by comparing the first vertical position limit value with the height measurand of the load-grappling devices.

This first vertical position deviation is adapted to indicate the state of the load-grappling devices at the approaching height. In the display 20, the state of being at the approaching height is indicated by changing the bar 58 dark.

In the condition of Figure 2, the bar 58 is dark, in which condition the load-grappling devices are at the approaching height. On the contrary, the second vertical position deviation is obtained by comparing the second vertical position limit value with, the height measurand of the load-grappling devices. This second vertical position deviation is adapted to indicate the state of the load-grappling devices at the handling height. In the display 20, the state of being at the handling height is indicated in the bar 56. The bar 56 is white at the top and otherwise grey, in which case the load-grappling devices must be lifted to achieve the handling height. Upon achieving the handling height, the bar 56 will change black.

In the view of the system according to the invention shown in Figure 2, the vertical position of the lift truck arms is shown with indicator bars 56, 58 on the right of the mast 49.

The view of the display is described below in more detail.

When the vertical position indicator bar 56 for the positioning changes from grey, as in the figure, to black, the forks are at such a height that the load can be placed onto the shelf. More precisely, the load is then at a sufficient height so that it does not contact the shelf level onto which it is being placed. On the other hand, the load is sufficiently low so as not to contact the above-located shelf level. The extent to which the load must be on top of the shelf in order to place the load safely on the shelf, depends on each particular case. Typically this value is approximately -15 cm. The distance programmed according to the load also remains between the load and the next shelf level.

Correspondingly, the indicator bar 58 shows the vertical position in which the load-grappling devices can be inserted under the load. The load-grappling devices are then at the approaching height. When black, the indicator bar 58 for the free arms indicates that the load is in place on the shelf and the arms can be retracted from under the load, as the arms are not contacting either the shelf or the load. Correspondingly, the indicator bar 58 shows the vertical position in which the arms can be inserted under the load when removing the load from the shelf.

The display view 20 of the system according to the invention shown in Figure 2 is adapted to indicate the shelf location.

Several shelf heights can have been stored in the system as limit values. In addition, the shelf heights stored as limit values can have been set to apply to a particular shelf type only. In this case the shelf type is typically indicated with a letter, such as letter C in the shelving display position 60 in Figure 2. The shelf number, in turn, is typically indicated with a number, such as number 1 in the shelf level display position 60' in Figure 2. Thus indication Cl means that the vertical position of the load is compared to the height of the shelf 1 of shelving C. When the operator is placing the load onto this particular shelf in this shelving, he sees the position of the lifting forks compared to the shelf level. In other words, the limit value relative to which the system compares the vertical position of the lifting forks is shown as a code in the display positions 60 and 60'.

The filling and color changes of the indicator bars assist the operator in guiding the load to the desired location, i.e. controlling the load in such a way that the measurand reaches the limit value. Since assisting is performed when required by the operator, and it is desired that the operator pays attention to central aspects, the indicator bars should not be enabled too early. In other words, the indicator bars are advantageously shown in the display only after the operator may need the information. For this reason, the display limits, which are used to adjust the enabling of the control bars, can be set for each specific case. For example, when assisting the operator in lifting a load to a correct shelf height, the display of the control bar can be adjusted such that the control bar is displayed 100 cm before the limit value. The control bar fills gradually when approaching the limit value.

Finally the control bar changes black indicating that the limit value has been reached. In Figure 2, the angle display limit is 5 , in which case the angle is shown when it is below 5 . The display bars can also be scalable, whereupon the angle range 62 shown in the angle display bar 46 depends on the measurand value.

The measurand can be sufficiently close to the limit value even before it has actually reached the limit value. The moment at which the measurand is sufficiently close to the limit value depends, however, on the parameter to be measured and the operating condition. For this reason, it is possible to set in the system allowable deviations specific for each parameter indicating how far the measurand can be from the limit value. In addition, the allowable deviation can be set separately on both sides of the limit value, as the limit value can be very strict for one side allowing, however, even a significant deviation on the other side. For example, when compressing the load, the limit value can be the highest allowable compression pressure. However, the load is kept between the load-grappling devices even with a lower compression pressure, which can be taken into account by setting the allowable deviation below the limit value.

Figure 3 shows a view of the system according to the invention in which the measurands are displayed mainly as numerical values. The horizontal position, i.e. the position under the load, is indicated by numerical values in the display area 64 and the vertical position of the load is indicated by numerical values in the display area 66. The angle, in turn, is shown in the display area 68. The angle, distance and vertical position are shown in selected units. The vertical position can be shown in centimeters or inches, for example.

The tilt angle of the lift truck mast is displayed, in addition to the numerical values of the display position 68, graphically by the angle display bar 46. The items shown in the view can be selected as specifically desired.

Figure 4 shows the main menu of the system according to the invention. The main menu can be accessed from the display showing information related to the load by pressing either the button C or button E. As regards the buttons, reference is made to Figure 1. The arrow buttons 40, 42 are used for browsing the main menu as well as other menus. Any of the following functions is selectable from the main menu 70: Select View 72, Limit Values 74, Profiles 76, General Settings 78, Information 80. By selecting the function "Select View" 72, the "Select View" submenu 82 shown in Figure 5 can be accessed.

Figure 5 shows the "Select View" submenu 82. By selecting "View" 84 it is possible to access directly to the view selected on the basic display. Selecting "Graphic" 86, in turn, accesses a graphic display, in which the selected parameters, such as the angle, distance and height, are shown as control bars. Selecting "Numerical Values" 88 accesses a numerical display, in which the selected parameters are shown numerically. By selecting further "Angle" 90, "Distance" 92, or "Height" 94, it is possible to access a view in which the parameter concerned is shown graphically and numerically. If the system is used for measuring additional parameters, the parameters are selected for display in this menu. Additional parameters to be measured and displayed can include the compression pressure and load weight, for example.

By selecting "Limit Values" 74 from the main menu shown in Figure 4, the operator accesses further to the "Limit Values" submenu, in which he can adjust the desired limit values. When the measuring parameters are angle, height and distance, like in the case of the "View" menu, the related limit values can be adjusted in this menu. The system compares the measurands to these set limit values. The parameter, for which one wants to adjust the limit value, is selected from the "Limit Values" submenu. By selecting a desired parameter the user accesses to the following submenu, in which it is possible to select one of the predefined limit values or add a new limit value. A new limit value can be set by entering it manually or based on the sensor measurement. For the angle, several limit values can be selected, in which case the system compares the actual angle, i.e. the measurand related to the angle, to the closest limit value for creating the deviation to be displayed.

Of several measurands, for which limit values can be set, the definition of limit values for the vertical position of the load is described here in more detail. Defining the limit values for the vertical position of the load means defining the targeted lifting height of the load. The desired lifting height can be selected from the menu or it can be created from the menu item "New". Selecting "New" allows entering a new limit value. When entering the vertical limit value of the load, information related to a new shelving can be entered into the system. First, the number of shelves comprised in the shelving is entered. After this, each shelf is defined a vertical position, i.e. the limit value. Two heights or limit values must be defined for each shelf height. The first of these levels is the one at which the load can be driven in place to the shelf location, in other words, the level, at which the load can be placed between the shelves. In this condition the top edge of the load must not contact the following shelf, i.e. the bottom part shelf, onto which the load is being lifted. At this height the load can thus be pushed between the shelves. The second of the levels, or limit values, defined for each shelf height determines at which height the lift truck arms must be in order that the arms can be retracted from under the pallet or pushed under the pallet without touching the pallet or the shelf. When setting levels, their setting can be carried out manually by entering the shelf heights, or based on the measuring results of the sensors.

The heights of the loads to be handled, i.e. how high the loads are, can be informed to the system, or the system can measure these. When the system compares this information to the information entered regarding the shelves, the system can alert if the operator tries to place the load into too confined a space. When the system compares both the top and the bottom surface of the loads to the shelf surfaces, the shelf heights can be set closer to the sizes of the stored loads compared to heretofore, which allows remarkable savings in the storage space.

The allowable deviation associated closely with the limit value can be adjusted separately for each limit value in the item "Hysteresis" of the "General Settings" menu. The allowable deviation can be set separately on both sides of the limit value.

In addition to the allowable deviations, display values are defined. These display values indicate when the control bars start showing the approaching of the limit value in the control bars. Advantageously approaching values can be defined between the allowable deviations and display values. When passing by these approaching values, i.e. when being between the approaching values and limit values, the control bar is shown with a more accurate scaling.

The modification capability of the system can be utilized in many other ways as well. For example, the equipment can be provided with different language versions and units according to the needs of the operator. When using a desired language version and familiar units, the usability increases dramatically. The operator must command the language particularly if he modifies the system settings. The modification capability of the system also increases by the fact that the measuring parameters and their units can be selected as desired for each specific case. In equipment according to prior art such modifications are much more expensive, it making such is possible at all.

One selection can also be a button lock, which can be used to ensure that changing the settings is not allowed without a password. The equipment operates, however, as normally, and the operator can change views, for example, but the operator cannot modify the settings. This is very practical in order that the operators can be sure about the current settings.

Advantageously there are several passwords each of which is assigned specific rights for modifying the settings.

Furthermore, a function allowing cycling of menus can be selectable. This allows moving from the last menu item to the top item by pressing the Down button. Keeping the background light switched on can be selected here. "Additional Settings" includes information on sensors and other. This information does not require changes afterwards unless sensors are changed. Therefore, "Additional Settings" are password protected to prevent changing them accidentally.

The profile defines which functions the system shows in each view. In the "Profile" menu, the desired profile can be directly loaded or a new profile can be created. The profiles can be user-specific. The profile to be used can also be selected based on the load used.

From the "Information" menu, contact data including the manufacturer's e-mail address and fax number, can be selected for display. The "Information" menu also contains the software version number and information on the lift truck used.

Figure 6 shows an operating condition of a lift truck which can be prevented with a system according to the invention.

This condition has appeared as the lift truck driver has not detected that the arms have been pushed behind the load 95 to be lifted, whereupon, when lifting the load 95, the load 96 located behind is also lifted. As the load located behind is placed on top of the forks only for a small part, it can fall over causing very significant problems. If a system according to the invention had been used, the driver would have noticed that the arms were pushed too far under the load. Then the driver could have backed up slightly so that the arms would have been positioned only under the load to be lifted.

Figure 7 shows an operating condition of the system according to the invention, in which the lift truck 100 is used to handle loads 104 stored in the shelving 102. The system 10 comprises a height sensor 28, from which the system 10 receives the measuring results related to the vertical position of the load. The system 10 can be programmed to stop the load-grappling devices 106 and thus the load 104 at a desired shelf height. The driver could guide the load incorrectly, for example too high, but the system can stop the load independent of the operator. Thus at least one parameter is controlled based on the deviation, i.e. the system comprises control means for controlling the parameter automatically. The control means are used to control the load such that it stops automatically at the shelf position.

Figure 7 shows an operating condition of a lift truck in which the lift truck is used for lifting a load onto a shelf. When lifting the load, it can be controllably stopped at the shelf position. Upon reaching a lifting height at which a possible stopping point is programmed for the load-grappling devices, such as a shelf location, the system examines the selected criterion, such as the movement speed, and compares it to the set criteria. A criterion can be for example that the load is stopped if the movement speed is under 80% of the maximum speed. If the movement speed equals or exceeds 80% of the maximum speed, the system's interpretation is that the operator does not want to stop the load at this height. When stopping at a shelf position, the load-grappling devices do not continue moving for a moment but remain stopped for five seconds, for example, providing the operator time for releasing the control to the basic state. Once the operator has released the control to the basic state, the load remains in place. If the user wants the load to continue moving, he keeps the control in the "On" position in which case the load continues moving.

The criteria based on which stopping is performed can be set as desired from the user interface. For example, it is possible to define as a criterion that stopping is performed when the movement speed is 80% of the maximum speed or below that. Instead of 80%, the criteria can include generally values between 50 -90%, advantageously between 70 -80 %. It is essential that stopping is performed only when the lifting speed clearly differs from the maximum *speed or from the lifting speed otherwise normally used in the work. Thus, if desired, the operator can pass by shelf levels without the system stopping the load at these positions. The system stops lifting only at those heights for which the set criteria are fulfilled allowing thus the work to be performed smoothly. The system provides the desired precision for finding the shelf levels improving thus the efficiency and reliability of operation. The work ergonomy also improves in many cases as the operator is not required to reach out from the lift truck to see the shelf levels.

The system can also be used for assisting monitoring of the task performed. For example, when loading a trailer truck, each load to be lifted can be weighed using the weighing sensors comprised in the system. The mass of the load is stored in the system, which enables the system to inform the operator when a correct amount of goods have been loaded to the trailer truck. In addition, the system in the lift truck can have a connection to a central system which registers the information related to the stuffed loads. Thus the central system knows the state of the storage.

The system can also be used for monitoring work time or measuring results of parameters. The parameter monitored can be for instance compression pressure used for grabbing the loads. The equipment can also be used for monitoring the lift truck condition. The equipment can monitor maintenance of pressure in cylinders. Defects are thus informed to the operator immediately even when small symptoms appear, which typically enables avoiding greater damage.

Related to exceeding of limit values, the system can inform its user in many different ways, but it is essential that the operator can see graphic information about a desired parameter.

For the indication, a display of a portable computer, pda or intelligent phone can be used. A great advantage provided by such equipment is that it would not be necessary to manufacture the entire system by oneself but devices offering ready-made versatile functions could be used as part of the system. Ready-made devices are generally also economically more advantageous than small batches of a particular special product manufactured as a special order. Advantageously the devices used as the display incorporate versatile wireless data transfer means, which can be used for transferring data to information systems. Information systems can exist for many purposes, for example, for monitoring the quantity of products in a storage.

When a display of a portable computer, pda or intelligent phone is used for indicating the deviation, in addition to the device used as the display, the system comprises a central unit, from which the device used as the display receives information via a serial cable or by using some wired or wireless protocol. As the keyboard, t is possible to use the keyboard of the device used as the display or a separate keyboard, which has been connected to the device used as the display or to the central unit. Programming can be carried out using a programming language which is device independent. Such a programming language is for instance JAVA. The platform, on which the application can be created, can be for instance Windows or Linux. A great advantage provided by such equipment would be that it would not be necessary to manufacture the entire system by oneself but devices offering ready-made versatile functions could be used as part of it. Ready-made devices are generally also economically more advantageous than small batches of a certain special product manufactured as a special order. Advantageously the devices used as the display incorporate versatile wireless data transfer means, which can be used for transferring data to information systems.

Information systems can exist for many purposes. An information system can be used, for example, for monitoring the quantity of products in a storage.

Claims

CLAIMS

1. A method for assisting a lift truck operator, in which method loads are handled using a lift truck comprising load-grappling devices, and parameters related to handling of loads are measured obtaining thereby measurands, and limit values corresponding to the measurands are entered into a system, and at least one of the measurands is compared to the set limit values corresponding to the parameter, and a deviation between the measurand and the limit value is obtained as the result of this comparison, characterized in that at least one deviation is indicated to the operator steplessly graphically.

2. A method according to Claim 1, characterized in at least two of the limit values are vertical position limit values of the load-grappling devices, and at least one of the measurands is the vertical position measurand of the load-grappling devices, and the vertical position measurand of the load-grappling devices is compared to at least two set vertical position limit values of the load-grappling devices obtaining thereby at least two vertical position deviations, and at least two vertical position deviations are indicated to the operator simultaneously steplessly graphically.

3. A method according to Claim 2, characterized in that the vertical position deviations are a first vertical position deviation and a second vertical position deviation with the first vertical position deviation indicating the state of the load-grappling devices at the approaching height and the second vertical position deviation indicating the state of the load-grappling devices at the handling height.

4. A method according to Claim 2 or 3, in which loads are positioned in shelf locations, and the shelf locations have shelf heights, characterized in that the vertical position limit values of the load-grappling devices are computed based on the shelf heights.

5. A method according to any of Claims 1 to 4, characterized in that at least one parameter is controlled automatically based on the deviation.

6. A method according to any of Claims 1 to 5, characterized in that the deviation is indicated to the operator at different times in different views.

7. A method according to Claim 6 or 7, characterized in that the view to be displayed is automatically selected based on measurands.

8. A method according to any of Claims 1 to 8, characterized in that there are several limit values at least per one measurand.

9. A system for assisting a lift truck operator in load handling comprising: -load-grappling devices for handling loads, -sensors for measuring the parameters related to load handling and for creating measurands, -limit value setting means for setting limit values, and -comparison means for comparing measurands and limit values and for creating a deviation, characterized in that the system further comprises: -a display for indicating at least one deviation steplessly graphically.

10. A system according to Claim 9, in which at least one of the sensors belonging thereto is a vertical position sensor for creating the vertical position measurand of the load-grappling devices, characterized in that -the limit value setting means comprise height limit value setting means for setting at least two vertical position limit values, -the comparison means are adapted to compare the vertical position measurand of the load-grappling devices at least to two vertical position limit values for creating a vertical position deviation, and -the display is adapted to indicate simultaneously at least two vertical position deviations stepiessly graphically.

11. A system according to Claim 10, characterized in that the vertical position deviations are a first vertical position deviation and a second vertical position deviation, and the first vertical position deviation is adapted to indicate the state of the load-grappling devices at the approaching height and the second vertical position deviation is adapted to indicate the state of the load-grappling devices at the handling height.

12. A system according to Claim 10 or 11, which is used for positioning loads in shelf locations, and the shelf locations have shelf heights, characterized in that the height limit value setting means are adapted to be used for entering the shelf heights to the system, and a vertical position limit value is adapted to be computed based on the shelf heights.

13. A system according to Claim 12, characterized in that the shelf location is adapted to be indicated in a display.

14. A system according to any of Claims 9 to 13, characterized in that the display is a liquid crystal display.

15. A system according to any of Claims 9 to 14, characterized in that the system includes control means for controlling a parameter automatically.

16. A system according to Claim 15, characterized in that the control means comprised in the system are adapted to automatically control the vertical position of the load-grappling devices.

17. A system according to any of Claims 9 to 16, characterized in that the display is adapted to show different views at different times.

18. A system according to Claims 1 to 17, characterized in that the limit value setting means are adapted to be used for entering several limit values at least per one measurand.

19. A method for assisting a lift truck operator substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

20. A system for assisting a lift truck operator substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.