Method for controlling the load part of a forklift truck

Abstract

A method for controlling the load part of an industrial truck, in which, upon actuation of a control element via a control device, a lifting unit raises or lowers the load part, wherein the load part is raised or lowered by a predetermined sequence of clicks with the control element, wherein the click sequence has predetermined intervals, characterized in that after completion of the click sequence on the control element, a dead time elapses until a drive unit of the industrial truck responds to a travel command, wherein raising or lowering of the load part or a mast of a lifting frame continues automatically until it is preset to end, wherein the automatic lifting or lowering function triggered by the click sequence of the control element is indicated visually and / or audibly.

Description

[0001] The invention relates to a method for controlling the load part of a forklift truck according to claim 1.

[0002] To lift and lower a load, industrial trucks have a lifting unit with at least one lifting drive that raises and lowers the load and / or the mast of a lifting frame. The lifting drive typically has at least one hydraulic cylinder supplied by an electrically driven hydraulic pump. When lifting, a distinction is made between an initial lift / additional lift and a standard mast lift to a predetermined height. During the initial lift, the load is raised only far enough for the industrial truck to move the load freely above the ground. Low-lift trucks have only an initial lift. High-lift trucks, which can raise the load to considerable heights, may also have an initial lift. For stacking and unstacking pallets in racks or similar structures, the load is raised or lowered to the desired height using the mast lift.The actuation of a control device that controls the process of the load part is usually carried out via a control element, whereby different control elements can be provided for raising and lowering, or a single rocker switch, whereby the rocker switch causes raising in one position and lowering in the other.

[0003] High-lift vehicles have an end-stop function for the lifting unit when the maximum lifting height or the lowering point is reached. This also applies to the mast of a lifting frame in its upper or lower end position. Reaching the upper or lower end position can be detected, for example, by monitoring the current of the electric motor driving the lifting unit or by monitoring the pressure in the hydraulic system of the lifting unit. It is also known to provide sensors or switches at the end positions that send a corresponding signal to the control device.

[0004] It is also common practice to preset the desired lifting height, for example when approaching shelves, using a lifting height sensor. When this sensor is triggered, the lifting or lowering process is stopped.

[0005] To raise or lower the load until the lifting mechanism stops, the control element must be held down continuously. While holding the control element down, the operator of the forklift truck can only perform other tasks to a limited extent. This results in a loss of productivity.

[0006] From DE 20 2014 000 309 U1, a pallet truck lifting system is known in which a lifting actuator, a lowering actuator, and a drive actuator are provided, connected to an electronic control unit. The electronic control unit is programmed to receive a drive command from a drive actuator and, in response to receiving the drive command after receiving the initial lifting command, causes the load to be lifted and the pallet truck to move. In other words, the lifting command is combined with a drive command so that movement of the pallet truck is possible immediately upon receiving the lifting command. It is also known in this context that a lifting command is achieved by repeatedly actuating the corresponding control element. The aim is to minimize the time elapsed between the lifting command and the movement of the pallet truck. The processes discussed relate to the free lift.

[0007] The invention therefore aims to provide a method for controlling the load section of a forklift truck in which the operator does not have to continuously operate the control element to perform a lifting or lowering operation. At the same time, the logical sequence of functions of the forklift truck should be ensured.

[0008] This problem is solved by the features of claim 1.

[0009] In the method according to the invention, the load is raised or lowered by a predetermined sequence of clicks at predetermined intervals using the control element, as is known per se. A certain dead time is provided for the control device, which must elapse after the completion of the click sequence before the drive system of the industrial truck responds to a travel command.

[0010] When a load component is mentioned above and below, this term includes both a load carriage with load forks and parts of a lifting frame (masts) that are raised or lowered for lifting or lowering.

[0011] In the method according to the invention, for example, a double-click of the control element within a predefined interval allows another function to be performed. One example is lifting the load to the end of its lifting range without having to continuously hold down the lifting button. In addition, other functions can then be controlled, such as lifting to a specific height using a lifting height sensor or lowering to floor or intermediate levels. According to the invention, the automatic lifting and lowering function, activated by multiple clicks of the control element, can be visually indicated by a symbol in a display element of the vehicle, for example, a screen. The automatic lifting and lowering function automatically continues raising or lowering the load or a mast of a lifting frame until it is stopped at a preset time.

[0012] From EP 1 398 251 B1 or EP 2 008 961 A1 it is known to operate a drive switch by a double-click. This makes it possible, for example, to switch the drive control of a forklift truck into a creep speed mode.

[0013] If the load is lifted by means of a double-click, it is naturally necessary to ensure that the lifting process is terminated. Therefore, one embodiment of the invention provides that the lifting process is terminated by • Reaching a stroke end sensor, • Reaching a preset value of a stroke height sensor, • Expiry of a predetermined lifting time, • sudden increase in the current of the lifting unit, • sudden increase in the hydraulic pressure of the lifting unit or • Operation of any control element other than the driving switch will end.

[0014] According to a further embodiment of the invention, the lowering process is carried out by • Reaching a sink end sensor, • Reaching a preset height of a lift height sensor, • Expiration of a predetermined lowering time, • Activation of any operating element other than the drive switch, or • Pressure drop of the hydraulic pressure of the lifting unit, is terminated.

[0015] The lifting or lowering process can also be terminated by confirming a standard control element that triggers a stop function, or by clicking the control element again.

[0016] According to one embodiment of the invention, a double-click actuation is preferably provided for raising and lowering.

[0017] The method according to the invention is advantageously applicable to both low-lift and high-lift vehicles. The achievement of an initial lift, for example in a low-lift vehicle, can be determined by a sensor, a defined lift time, a defined current increase of the motor of the lifting unit, or a defined pressure increase of the hydraulic lifting unit. Upon reaching a mechanical lift stop or a fixed obstacle, the current increase is much higher than during the lifting of the load.

[0018] With high-lift vehicles, a distinction must be made between lifting the load freely and lifting it in other ways. Therefore, one embodiment of the invention provides that, to differentiate whether the load should be lifted freely with the mast stroke or raised further, the control device detects different intervals of multiple clicks (double clicks) or a different number of clicks on the actuating element. This naturally also applies to lowering to a certain height or to the floor or shelf compartment. Reaching a lowered position can be determined not only by sensor sensing or by measuring the lowering time, but also by a defined pressure drop in the hydraulic system. According to a further embodiment of the invention, a double click is provided for lifting to a predetermined height. A triple click allows the load to be lifted freely with the mast stroke.

[0019] It is also conceivable to initiate raising and lowering not only through multiple clicks but also through continuous operation of the control element, as is currently common practice. In this case, the control system must differentiate between the two types of operation. The raising or lowering process can only be initiated once the control device detects that no double or triple click has been performed. This means that the time period specified for a double or triple click after the initial activation of the control element must elapse before continuous operation of the control element results in a raising or lowering process.

[0020] In the method according to the invention, after performing a series of clicks, the operator can immediately start the industrial truck without having to attend to the lifting process any further. As already mentioned, a delay time can be set before the industrial truck starts moving to prevent the unpicked load from being lost. Conversely, the lowering process must also be completed before the load moves away from the truck.

[0021] The invention is explained in more detail below with reference to a drawing.

[0022] The single figure shows a schematic block diagram to illustrate the method according to the invention.

[0023] A load component / lifting frame is actuated by a lifting cylinder or a lifting spindle. Each load component or lifting frame is equipped with a stroke end sensor, a lowering sensor, and a height sensor, the latter continuously measuring the lifting height of the load component. The lifting cylinder or lifting spindle is actuated by a lifting unit, which in turn receives its commands from a control device. The current from the lifting unit's motor and the pressure of the hydraulic pump are measured and reported to the control unit. Operating elements, such as those for raising and lowering the load component or lifting frame, as well as display elements, are connected to the control unit.

[0024] By activating a control element, for example by double-clicking, the load or a mast of a lifting frame is raised or lowered and continues automatically until it is stopped by a preset mechanism, such as a lift end sensor, a preset lifting height, or a lift-lower sensor. The process can also be terminated after a preset time in the control system or by detecting current and / or pressure in the lifting unit, which indicates when a predetermined lifting height has been reached. To distinguish between lifting the load freely and a "normal lift," a double-click of the control element raises the load to any desired height, while a triple-click simply lifts the load freely.It is also possible to differentiate between free lifting and normal lifting by using different intervals between clicks.

Claims

[1] Method for controlling the load part of an industrial truck, wherein, when an operating element is actuated via a control device, a lifting unit raises or lowers the load part, wherein the load part is raised or lowered by a predetermined sequence of clicks with the operating element, wherein the sequence of clicks has predetermined intervals, characterized by , that after completion of the click sequence on the control element, a dead time elapses until a drive unit of the industrial truck responds to a travel command, whereby raising or lowering of the load part or a mast of a lifting frame continues automatically until it is preset to end, whereby the automatic lifting or lowering function triggered by the click sequence of the control element is indicated visually and / or audibly. [2] Method according to claim 1, characterized by that the lifting process by • Reaching a stroke end sensor, • Reaching a preset value of a stroke height sensor, • Expiry of a predetermined lifting time, • sudden increase in the current of the lifting unit, • sudden increase in the hydraulic pressure of the lifting unit or • Operation of any control element other than a drive switch is terminated. [3] Method according to claim 1 or 2, characterized by that the lowering process is caused by • Reaching a sink end sensor, • Reaching a preset height of a lift height sensor, • Expiry of a predetermined lowering time, • Activation of any operating element other than the drive switch or • The pressure drop in the hydraulic pressure of the hydraulic unit is stopped. [4] Method according to any one of claims 1 to 3, characterized by , that the control element for raising and / or lowering is activated with a double-click. [5] Method according to any one of claims 1 to 4, characterized by , that to distinguish whether the load part is only to lift the load free or to lift it further, the control device detects different intervals of multiple clicks (double click) or a different number of clicks. [6] Method according to claim 5, characterized by , that a double-click is intended for lifting to a predetermined height and a triple-click for lifting the load free. [7] Method according to any one of claims 1 to 6, characterized by , that a lifting or lowering operation is also triggered by a continuous operation of the control element for lifting and / or lowering and the control device delays the lifting or lowering operation for a predetermined period of time which is equal to or greater than the predetermined total duration of the clicks on the actuating element.

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