Low-lift industrial truck and method for operating the same

Abstract

A low-lift industrial truck (2) and a method for operating the same. The industrial truck includes a load fork (4) for picking up a load. Fork tines (6a, 6b) of the load fork (4) each include at least one load roller (8) in a region of fork tine tips (28). The industrial truck also includes a load lifting assistance system having a distance sensor (16) and a processing unit (14). The distance sensor is configured to measure a distance between the load and a front wall (12) of the industrial truck facing the load fork. At least one distance between the load and the front wall is saved in the processing unit and corresponds to a predetermined stop position. The processing unit is configured to process measured values of the distance sensor and to generate a stop signal when a distance corresponding to the stop position (20a, 20b) is determined.

Claims

1. A low-lift industrial truck for picking up and moving a load, the low-lift industrial truck comprising: a load fork for picking up the load, said load fork having fork tines with fork tine tips; and a load lifting assistance system that comprises a distance sensor and a processing unit; wherein fork tines of the load fork each comprise at least one load roller in a region of the fork tine tips, wherein the distance sensor is configured to measure a distance between the load to be picked up by the load fork and a front wall of the industrial truck facing the load fork for processing by the processing unit, wherein at least one distance between the load to be picked up by the load fork and the front wall is saved in the processing unit as a predetermined stop position, wherein the processing unit is configured to generate a stop signal when the distance between the load to be picked up by the load fork and the front wall of the industrial truck facing the load fork measured by the distance sensor corresponds to the predetermined stop position saved in the processing unit, wherein the industrial truck further comprises an acceleration sensor configured to measure a vertical acceleration of the load fork in the region of at least one fork tine tip, wherein the processing unit is configured to process measured values of the acceleration sensor and to detect a presence or absence of a vertical acceleration event, wherein a first distance of a first stop position for pallet transverse insertion and a second distance of a second stop position for pallet longitudinal insertion are saved in the processing unit, and wherein the processing unit is configured to generate the stop signal at the second stop position when: the distance measured by the distance sensor is less than or equal to the distance of the first stop position; and the presence of the vertical acceleration event is not detected.

2. The industrial truck according to claim 1, wherein the processing unit is further configured to output an alert signal to an acoustic and/or visual output unit when the stop signal is generated.

3. The industrial truck according to claim 1, wherein the processing unit is further configured to stop the industrial truck when the stop signal is generated.

4. The industrial truck according to claim 3, wherein the processing unit is further configured to automatically lift the load fork when the stop signal is generated.

5. The industrial truck according to claim 1, wherein at least one set acceleration parameter characteristic for the vertical acceleration event is saved in the processing unit, and wherein the processing unit is configured to detect the presence of the vertical acceleration event when the at least one set acceleration parameter characteristic is exceeded.

6. The industrial truck according to claim 1, wherein a detection zone is saved in the processing unit, wherein the detection zone extends, at least sectionally, in a fork direction between the first stop position and the fork tine tips, and wherein the processing unit is configured to detect and process measured values of the acceleration sensor when it is determined that the load to be picked up by the load fork is located within the detection zone with reference to the measured distance of the load to be picked up by the load fork.

7. The industrial truck according to claim 6, wherein the load rollers lie at least sectionally within the detection zone.

8. The industrial truck according to claim 6, wherein the detection zone in the fork direction has a length greater than or equal to 227 mm.

9. The industrial truck according to claim 1, wherein detection zone is saved in the processing unit, wherein the detection zone extends in a fork direction starting from the tip region of the fork tines up to a first limit that lies at a safety distance in front of the tip region of the fork tines, and wherein the processing unit is configured to limit a driving speed of the industrial truck to a predetermined value when a measured value of the distance of the load lies within the detection zone.

10. The industrial truck according to claim 1, wherein a detection zone is saved in the processing unit, wherein the detection zone extends in a fork direction starting from a predetermined minimum distance to the front wall, wherein the predetermined stop position lies within the detection zone, and wherein the processing unit is configured to limit a driving speed of the industrial truck to a predetermined value when it is determined that the load is within the detection zone with reference to the measured distance of the load.

11. A method for operating a low-lift industrial truck for picking up a load having a load fork for picking up the load, said load fork having fork tines with fork tine tips and at least one load roller in a region of each of the fork tine tips, the method comprising steps of: driving the industrial truck at a driving speed in a fork direction toward the load before picking up the load with the load fork; and determining a distance between the load and a front wall of the industrial truck facing the load fork during the driving step with a load lifting assistance system of the industrial truck that comprises a distance sensor and a processing unit, wherein at least one distance between the load and the front wall is saved in the processing unit as a predetermined stop position; and generating a stop signal when the distance determined by the distance sensor in the determining step corresponds to the stop position saved in the processing unit wherein the industrial truck comprises an acceleration sensor configured to measure a vertical acceleration of the load fork in the region of at least one fork tine tip, wherein a first distance of a first stop position for pallet transverse insertion and a second distance of a second stop position for pallet longitudinal insertion are saved in the processing unit, and wherein when a distance is detected that is less than or equal to the distance of the first stop position and a vertical acceleration event is not detected, the stop signal is generated at the second stop position.

12. The method according to claim 11, further comprising outputting an alert signal in an acoustic and/or visual output unit when the stop signal is generated.

13. The method according to claim 11, further comprising stopping the industrial truck when the stop signal is generated.

14. The method according to claim 13, further comprising automatically lifting the load fork when the stop signal is generated.

15. The method according to claim 11, wherein at least one set acceleration parameter characteristic for the vertical acceleration event is saved in the processing unit, and wherein a vertical acceleration event is detected when the at least one set acceleration parameter is exceeded.

16. The method according to claim 11, wherein detection zone is saved in the processing unit, wherein the detection zone extends, at least sectionally, in the fork direction between the first stop position and the fork tine tips, and wherein measured values of the acceleration sensor are detected and processed with respect to the presence or absence of the vertical acceleration event when it is determined that the load is located within the detection zone with reference to the measured distance of the load.

17. The method according to claim 11, wherein a detection zone is saved in the processing unit that extends in the fork direction starting from the fork tine tips up to a first limit that lies at a safety distance in front of the fork tine tips, and when a distance is measured that lies within the detection zone, the driving speed of the industrial truck is limited to a predetermined value.

18. The method according to claim 11, wherein a detection zone is saved in the processing unit that extends in the fork direction starting from a minimum distance to the front wall, wherein the predetermined stop position lies within the detection zone, and wherein the driving speed of the industrial truck is limited to a predetermined value when the distance of the load is determined that lies within the detection zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described below, without restricting the general idea of the invention, based on exemplary embodiments in reference to the drawings, whereby we expressly refer to the drawings with regard to all details according to the invention that are not explained in greater detail in the text. In the figures:

(2) FIG. 1 shows a schematically simplified plan view of an industrial truck that represents the three provided detection zones,

(3) FIG. 2 shows a schematically simplified plan view of an industrial truck, wherein potential positions are represented by way of example for the acceleration sensor,

(4) FIG. 3a, 3c show schematically simplified plan views of a pallet,

(5) FIG. 3b, 3d show schematically simplified side views of a pallet from different directions, wherein FIG. 3b shows a longitudinal side, and FIG. 3d shows a transverse side of the pallet,

(6) FIGS. 4a to 4d show a schematically simplified plan view of an industrial truck that is performing a longitudinal insertion into a pallet in different phases during this process,

(7) FIGS. 5a to 5d show a schematically simplified plan view of an industrial truck that is performing a pallet transverse insertion during different phases of this process,

(8) FIGS. 6a to 6d show a schematically simplified side view of an industrial truck during a pallet transverse insertion, and

(9) FIG. 7 shows a time-dependent representation of measured values recorded by an acceleration sensor for the vertical acceleration during such a pallet transverse insertion.

(10) In the drawings, the same or similar elements and/or parts are provided with the same reference numbers in each case; a reintroduction will therefore always be omitted.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 1 shows a schematically simplified plan view of a low-lift industrial truck 2 which will also be generally termed an industrial truck in the context of the present description. This comprises a load fork 4 for picking up a load (not shown). The load is, for example, a commodity arranged on a pallet (also not shown), wherein the pallet together with the commodity is considered the load. The load fork 4 comprises two fork tines 6a, 6b that each for example comprise a load roller 8 in the region of the respective fork tine tip 28. It is also provided that a plurality of load rollers 8 are on the fork tine tips 28.

(12) The industrial truck 2 furthermore comprises a housing 10 on which are operating elements (not shown) for operating the industrial truck 2. The housing 10 comprises a front wall 12 facing the load fork 4. Within the housing 10 is a processing unit 14, wherein it is for example a computer, microcontroller or the like. It is also provided that the processing unit 14 is implemented as part of the control of the industrial truck 2. The processing unit 14 is coupled to a distance sensor 16 via a data link. The distance sensor 16 is for example an ultrasonic sensor, a laser rangefinder or a radar rangefinder as well. For example, the distance sensor 16 is positioned in the front wall 12 of the housing 10 of the industrial truck 2.

(13) The distance sensor 16 is configured to measure a distance between the load and the front wall 12 of the industrial truck 2 facing the load fork 4. This is indicated schematically and as an example by the schematically portrayed shaft fronts 18. The measured values detected by the distance sensor 16 are forwarded to the processing unit 14 which is configured to process these measured values from the distance sensor 16 and determine a distance of the load from the front wall 12 of the industrial truck 2 from them. To the extent that the load is already on the load fork 4 of the industrial truck 2, a longitudinal position of the load on the load fork 4 can be determined from the distance.

(14) Furthermore, two stop positions are defined, for example: A first stop position 20a for pallet transverse insertion, and a second stop position 20b for pallet longitudinal insertion. These stop positions 20a, 20b serve to correctly position the pallet on the load fork 4 so that it can be lifted with the load fork 4 without damaging the pallet. Moreover, a collision of the load with the front wall 12 of the industrial truck 2 is avoided. Conventionally, the stop positions are fork marks that are on the load fork 4 and are monitored by the operator of the industrial truck during the pickup process by visual monitoring. With the industrial truck 2 according to the described exemplary embodiment, the stop positions 20a, 20b are saved in the processing unit 14. The processing unit 14 is furthermore configured to generate a corresponding stop signal when a value is measured with the distance sensor 16, from which it is deducible that the load is located at one of the stop positions 20a, 20b.

(15) The processing unit 14 is furthermore configured to output an alert signal, for example, when the stop signal is present. This is accomplished for example by an acoustic and/or visual output unit 22. For example, a light signal or a display is generated that indicates to the operator of the industrial truck 2 that the load is at the relevant stop position 20a, 20b, or an acoustic alert signal sounds. The processing unit 14 is furthermore configured for example to stop the industrial truck 2 when one of the stop positions 20a, 20b has been reached. Furthermore, the industrial truck 2, or respectively its processing unit 14, is configured to automatically lift the load fork 4 when the relevant stop position 20a, 20b has been reached.

(16) Which of the two stop positions 20a, 20b are relevant for generating the stop signal depends on whether a pallet transverse insertion or a longitudinal insertion is occurring. The industrial truck 2 is capable of determining the type of insertion. In this regard, the industrial truck 2 comprises an acceleration sensor 24 that is configured to measure a vertical acceleration of the load fork 4 in the region of the fork tine tip 28. Since the load rollers 8 traverse a plank, for example a wood plank, of the pallet during the pallet transverse insertion, a vibration event occurs in the region of the fork tine tips 28. This vertical acceleration event that arises from the vibration, or respectively the shock in the region of the load rollers 8 when traversing the wood planks, alerts the industrial truck 2 to the fact that a pallet transverse insertion is occurring. Accordingly, the first stop position 20a relevant for the pallet transverse insertion is the stop position at which the stop signal is generated.

(17) In order to establish whether it is a pallet transverse insertion or a pallet longitudinal insertion, the processing unit 14 of the industrial truck 2 not only detects whether a vertical acceleration event is occurring, it also measures the distance between the front wall 12 and the load with the assistance of the distance sensor 16. The type of pallet insertion can be determined from these two parameters, and the stop position appropriate for the type of pallet insertion can be selected.

(18) If for example a distance value is detected that is less than or equal to a distance to the first stop position 20a, while at the same time a vertical acceleration event was not detected during insertion into the pallet, this means that the load rollers 8 have not traversed a plank of the pallet. Consequently, it must be a pallet longitudinal insertion, and the relevant stop position is therefore the second stop position 20b. Accordingly, the industrial truck 2 is stopped at the second stop position 20b, or a corresponding alert signal is output.

(19) For example, a plurality of detection zones are saved in the processing unit 14, i.e., a first detection zone 26a, a second detection zone 26b, and a third detection zone 26c.

(20) The first detection zone 26a extends in the fork direction GR starting from the fork tine tips 28 up to a first limit G1. The first limit G1 is at a safety distance A in front of the fork tine tips 28. The processing unit 14 is configured to limit the driving speed of the industrial truck 2 to a predetermined first value when a measured distance between the front wall 12 of the industrial truck 2 and the load lies within the first detection zone 26a. The industrial truck 2 is braked in other words when it approaches the load and the load is within the first detection zone 26a and only moves further at a reduced speed. The first value of the driving speed is less than a value of the routine or normal driving speed of the industrial truck 2 in handling mode.

(21) The second detection zone 26b extends in the fork direction GR, wherein the load rollers 8 lie at least sectionally within the second detection zone 26b. In the portrayed exemplary embodiment, the second detection zone 26b extends from a second limit G2 in the fork direction GR up to the fork tine tips 28. For example, the second detection zone 26b ends opposite the fork direction GR shortly or directly after the load rollers 8. In the portrayed exemplary embodiment, the load rollers 8 lie completely within the second detection zone 26b. The second detection zone 26b extends in particular up to the first detection zone 26a, and the transition between the first detection zone 26a and the second detection zone 26b lies within the region of the fork tine tips 28, for example at the outer end of the fork tine tips 28, or shortly before as in the portrayed exemplary embodiment.

(22) The processing unit 14 is furthermore configured, for example, to detect and process measured values of the acceleration sensor 24 when a position of the load is determined with reference to the measured value of the longitudinal position that lies within the second detection zone 26b. In the event that a vertical acceleration event is detected that for example is triggered by traversing the planks of a pallet, the first stop position 20a for pallet transverse insertion is established as the stop position. If there is no vertical acceleration event, the second stop position 20b is established as the stop position for pallet longitudinal insertion.

(23) The third detection zone 26c extends in the fork direction GR starting from a minimum distance to the front wall 12, wherein the predetermined stop position, i.e., the first stop position 20a for pallet transverse insertion and the second stop position 20b for pallet longitudinal insertion, lies within the third detection zone 26c. In the portrayed exemplary embodiment, the third detection zone 26c extends from a third limit G3 in the fork direction GR up to the second limit G2. The third limit G3 is determined so that the minimum distance between the third limit G3 and the front wall 12 of the industrial truck 2 is maintained. The predetermined stop positions 20a, 20b lie within the third detection zone 26c. The processing unit 14 is configured to determine a position of the load with reference to the measured value of the longitudinal position and, to the extent that it lies within the third detection zone 26c, to further reduce the driving speed of the industrial truck 2, i.e., to a second predetermined value. The second predetermined value for the driving speed lies below the aforementioned first value, which means that the driving speed of the industrial truck 2 is further reduced. This serves to prevent a collision of the load with the front wall 12 of the industrial truck 2 and to allow the industrial truck 2 to reliably and safely stop at the respectively relevant stop position 20a, 20b.

(24) FIG. 2 shows a further schematically simplified plan view of the industrial truck 2. For example, the possible positions are shown for the acceleration sensor 24. As already mentioned in conjunction with FIG. 1, the acceleration sensor 24 can be arranged in the region of the fork tine tip 28. It is however also provided that this is located within the fork tine 6a or 6b, and an arrangement in the rear region of the fork tines 6a, 6b is also possible. Since the vibration frequently continues into the housing 10 of the industrial truck 2 when traversing the wood plank of the pallet, it is also provided that the acceleration sensor 24 can be arranged in the region of the housing 10.

(25) FIG. 3a shows a schematically simplified plan view of a pallet 30, and FIG. 3b shows the associated side view of the pallet 30. It is a wood pallet only as an example. During longitudinal insertion, the fork tines 6a, 6b are inserted into the gaps 32a, 32b visible in this side view. FIG. 3c show another schematically simplified plan view of the pallet 30, and FIG. 3d shows the associated side view. During transverse insertion, the fork tines 6a, 6b are inserted into the gaps 33a, 33b. In this case, the load rollers 8 traverse the first wood plank 34a and the second wood plank 34b.

(26) FIGS. 4a to 4d show a schematically simplified plan view of an industrial truck 2 during a pallet longitudinal insertion in different phases during this process. In FIG. 4a, the industrial truck 2 approaches the pallet 30, and the pallet 30 enters into the first detection zone 26a. Accordingly, the driving speed of the industrial truck 2 is reduced. At a reduced speed, the industrial truck 2 approaches the pallet 30 until, as shown in FIG. 4b, the fork tine tips 28 of the industrial truck 2 enter into the gaps 32a, 32b in the pallet 30. At that moment, the pallet 30 enters into the second detection zone 26b, and the acceleration sensor 24 reads out. Since a vertical acceleration event does not occur during longitudinal insertion because the wood plank 34a (see FIG. 3d) is not traversed, the processing unit 14 detects a longitudinal insertion and defines the second stop position 20b as the stop position for the pallet insertion. This situation is shown in FIG. 4c. If the pallet 30 then enters into the third detection zone 26c, the driving speed of the industrial truck 2 is further reduced so that it then comes to a stop when the pallet 30 is located at the second stop position 20b. This situation is shown in FIG. 4d. Upon reaching the second stop position 20b, the load that consists of for example the pallet 30 and a commodity loaded thereupon is automatically lifted. It can also be provided that only a visual or acoustic alert signal is output.

(27) FIGS. 5a to 5d show other schematically simplified plan views of an industrial truck 2 that is performing a pallet transverse insertion during different phases of this process. The industrial truck 2 approaches the pallet 30, and the load enters into the first detection zone 26a. This situation is shown in FIG. 5a. The speed of the industrial truck 2 is reduced, and the industrial truck 2 approaches the pallet 30 at a reduced speed. Once the fork tine tips 28 reach the load, they enter into the second detection zone 26b; this situation is shown in FIG. 5b. The acceleration sensor 24 is read out when the load rollers 8 traverse the first wood plank 34a and a vertical acceleration event is detected. This occurs shortly after the position shown in FIG. 5. The presence of the vertical acceleration event causes the first stop position 20a to be defined as the stop position and, once the load enters into the third detection zone 26c, the industrial truck 2 inserts the fork tines 6a, 6b into the gaps 33a, 33b at a reduced speed until the first stop position 20a is reached.

(28) FIGS. 6a to 6d show schematically simplified side views of the industrial truck 2 during the process described in conjunction with FIGS. 5a to 5d. In this case, the situation in FIG. 6a corresponds to the plan view in FIG. 5a, the situation in FIG. 6b corresponds to the plan view in FIG. 5b, etc. The first to third detection zones 26a, 26b and 26c are also represented schematically simplified in FIG. 6a.

(29) FIG. 7 shows a time-dependent representation of measured values recorded by the acceleration sensor 24 for the vertical acceleration during a pallet transverse insertion. The approach to the pallet 30 occurs during the time period (1). During the time period (2), the first wood plank 34a of the pallet 30 is traversed; correspondingly, a first vertical acceleration event 36a is identified. Such a vertical acceleration event is for example detected with reference to exceeding a set limit value 38 for the vertical acceleration “a”. During time period (3), the second wood plank 34b of the pallet 30 is approached, and during time period (4), the second wood plank 34b is traversed. Correspondingly, a second vertical acceleration event 36b occurs. During time period (5), the stop position is approached until the industrial truck 2 stops.

(30) All named features, including those taken from the drawings alone as well as individual features that are disclosed in combination with other features, are considered, alone and in combination, to be essential for the invention. Embodiments according to the invention can be fulfilled by individual features or a combination of several features.

LIST OF REFERENCE CHARACTERS IN DRAWING FIGURES

(31) 2 Low-lift industrial truck

(32) 4 Load fork

(33) 6a, 6b Fork tine

(34) 8 Load roller

(35) 10 Housing

(36) 12 Front wall

(37) 14 Processing unit

(38) 16 Distance sensor

(39) 18 Shaft front

(40) 20a First stop position

(41) 20b Second stop position

(42) 22 Output unit

(43) 24 Acceleration sensor

(44) 26a First detection zone

(45) 26b Second detection zone

(46) 26c Third detection zone

(47) 28 Fork tine tip

(48) 30 Pallet

(49) 32a, 32b Gap (pallet longitudinal insertion)

(50) 33a, 32b Gap (pallet transverse insertion)

(51) 34a First wood plank

(52) 34b Second wood plank

(53) 36a First vertical acceleration event

(54) 36b Second vertical acceleration event

(55) 38 Limit value

(56) A Safety distance

(57) GR Fork direction

(58) G1 First limit

(59) G2 Second limit

(60) G3 Third limit