Fork insertion lifting device

Abstract

This invention provides a forklift that can reduce the time required to adjust the height of the forks to match the height of the pallet's insertion opening. [Solution] A lifting mechanism raises and lowers the forks. A control unit controls the lifting mechanism based on the sensor's detection results. The sensor detects obstacles diagonally above the straight line extending the forks, and obstacles on the straight line extending the forks. When the forks are positioned opposite the pallet and raised to the height of the pallet's insertion opening, the control unit starts the forks rising. When the sensor detects an obstacle diagonally above, or when no obstacles are detected thereafter, the control unit reduces the fork's rising speed. When an obstacle is detected on the straight line extending the forks, or when no obstacles are detected thereafter, the control unit stops the forks from rising.

Description

Technical Field

[0001] The present invention relates to a fork insertion lifting device.

Background Art

[0002] An automatic guided forklift (AGF) is used for the cargo handling work within the work area. The automatic guided forklift performs the cargo handling work by inserting the forks into the insertion opening of the pallet. In order to insert the forks into the insertion opening of the pallet, the height of the forks must be adjusted to the height of the insertion opening of the pallet. Patent Document 1 below discloses a forklift capable of detecting the position of the insertion opening of the pallet.

[0003] The forklift disclosed in Patent Document 1 has a horizontal sensor, an upward sensor, and a downward sensor attached to the tip of the fork. The horizontal sensor, the upward sensor, and the downward sensor detect obstacles in the horizontal direction, the obliquely upward direction, and the obliquely downward direction in front of the fork, respectively. Hereinafter, a method for detecting the insertion opening of the pallet will be described.

[0004] With the forks facing the pallet, the forks are lifted from below the pallet. First, the lower end of the pallet is detected by the upward sensor. Further, when the forks are lifted and the detection range of the upward sensor reaches the insertion opening of the pallet, no obstacle is detected by the upward sensor. Thus, based on the change in the detection result by the upward sensor, the insertion opening is detected.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The vertical dimensions of the pallet insertion openings are decreasing year by year. After the forks are adjusted to the height of the insertion opening, the automated guided transport (AGP) forklift moves forward towards the pallet, inserting the forks into the insertion space within the pallet. If the direction of movement of the forks is not parallel to the top and bottom surfaces of the insertion space, the tips of the forks may come into contact with the top or bottom surface of the insertion space during the insertion operation. If the forks come into contact with the top or bottom surface of the insertion space, it may cause the load to collapse. Furthermore, it is desirable to shorten the time required to adjust the height of the forks to the height of the pallet insertion opening.

[0007] The objective of the present invention is to provide a fork insertion and lifting device that can shorten the operating time required to adjust the height of the forks to match the height of the pallet insertion opening. [Means for solving the problem]

[0008] According to one aspect of the present invention, A fork and A lifting mechanism for raising and lowering the fork, Sensors and, A control unit that controls the lifting mechanism based on the detection result of the sensor. Equipped with, The sensor detects obstacles diagonally above the straight line extending the fork, and obstacles on the straight line extending the fork. When the fork is positioned opposite the pallet and raised to the height of the pallet's insertion opening, The control unit, The fork is made to start rising, When the sensor detects an obstacle diagonally above, or when no obstacle is subsequently detected, the upward speed of the fork is reduced. A fork insertion and lifting device is provided that stops the fork from rising when an obstacle is detected on the straight line extending from the fork, or when no obstacle is subsequently detected. [Effects of the Invention]

[0009] This reduces the time required to adjust the height of the forks to match the height of the pallet's insertion opening. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic side view of an automated transport forklift according to one embodiment. [Figure 2] Figure 2 is a schematic perspective view of the tip of the fork to which the sensor is attached. [Figure 3] Figure 3 is a perspective view showing the positional relationship between the pallet being handled and the forks. [Figure 4] Figure 4 is a schematic cross-sectional view of the point at which the forks begin to be inserted into the pallet's insertion slot. [Figure 5] Figures 5A to 5C are schematic cross-sectional views showing the positional relationship between the pallet and the fork 11 from the start of fork insertion to during insertion. [Figure 6] Figures 6A to 6E are schematic cross-sectional views showing the positional relationship between the pallet and the forks from the start of fork insertion to during insertion. [Figure 7] Figure 7 is a flowchart showing the control procedure performed by the control unit during the fork insertion operation. [Figure 8] Figures 8A to 8E are schematic cross-sectional views showing the positional relationship between the forks and the insertion opening when an automated transport forklift according to another embodiment raises its forks. [Figure 9] Figure 9 is a flowchart showing the control procedure when an automated guided forklift, according to the embodiments shown in Figures 8A to 8E, raises its forks. [Figure 10] Figure 10 is a flowchart showing the control procedure when an automated transport forklift raises its forks, based on a modified example of the embodiment shown in Figures 8A to 8E. [Modes for carrying out the invention]

[0011] Referring to FIGS. 1 to 7, a forklift according to an embodiment will be described. The forklift according to this embodiment is an automatic transport forklift.

[0012] FIG. 1 is a schematic side view of the automatic transport forklift 10 according to this embodiment. A mast 15 and wheels 18 are attached to the vehicle body 19. A motor 17 drives the wheels 18. Two forks 11 are supported by the mast 15 so as to be able to move up and down. A lifting mechanism 12 raises and lowers the forks 11. The fork 11 is composed of a part of an L-shaped member, and the L-shaped member includes a portion extending substantially horizontally forward from the bent portion and a portion extending substantially vertically upward. The fork 11 is composed of a portion extending forward from the bent portion. The L-shaped member is supported by the lifting mechanism 12 so as to be tiltable at a fulcrum 14 located at the upper end of the portion extending upward from the bent portion.

[0013] A tilt mechanism 13 tilts the fork 11. Here, "tilt" means an operation of tilting the fork 11 upward or downward with respect to the horizontal plane. For example, when the tilt mechanism 13 pushes the bent portion of the L-shaped member forward, the fork 11 tilts upward, and when it is pulled backward, the fork 11 tilts downward. The control unit 50 mounted on the vehicle body 19 controls the lifting mechanism 12 to raise and lower the fork 11. The control unit 50 controls the tilt mechanism 13 to tilt the fork 11.

[0014] A plurality of sensors 20 are attached to the tip of the fork 11. Hereinafter, the sensor 20 will be described with reference to FIG. 2.

[0015] FIG. 2 is a schematic perspective view of the tip of the fork 11 to which the sensor 20 is attached. A front direction sensor 20M, a downward direction sensor 20L, and an upward direction sensor 20U are attached to the tip of the fork 11. The front direction sensor 20M detects an obstacle within the detection distance SD in the front direction 21M of the fork 11. The downward direction sensor 20L is at an angle θ with respect to the extension line 30 of the fork 11 LIt forms a diagonal downward direction 21L and detects obstacles within detection distance SD. The upward sensor 20U is at an angle θ with respect to the extension line 30 of the fork 11. U It forms a beam that moves diagonally upward and detects obstacles within a detection distance SD of 21U. The detection distance SD is, for example, about 70mm to 100mm.

[0016] For example, a photoelectric sensor can be used as the front direction sensor 20M, the upward direction sensor 20U, and the downward direction sensor 20L, which illuminate an obstacle and detect the reflected light from the obstacle. Alternatively, a sensor that scans the light illuminating the obstacle in the vertical direction may be used to detect obstacles in the front direction, diagonally upward direction, and diagonally downward direction with a single sensor.

[0017] When the sensor 20 detects an obstacle, it outputs a detection signal. The detection signal is input to the control unit 50 (Figure 1). Based on the detection signal from the sensor 20, the control unit 50 controls the lifting mechanism 12, the tilt mechanism 13, and the motor 17.

[0018] Figure 3 is a perspective view showing the positional relationship between the pallet 60 to be handled and the forks 11. The pallet 60 includes multiple top plates 61, multiple bottom plates 62, and multiple beams 63 that connect the top plates 61 and bottom plates 62 at intervals. Two insertion openings 65 are provided, enclosed by the top plates 61, bottom plates 62, and beams 63. Two forks 11 are inserted into the space inside the pallet 60 through the two insertion openings 65, and the handling operation is performed.

[0019] Next, with reference to Figures 4 to 7, the control during the operation of inserting the fork 11 into the insertion opening 65 of the pallet 60 will be described.

[0020] Figure 4 is a schematic cross-sectional view of the moment when the forks 11 begin to be inserted into the insertion opening 65 of the pallet 60. The forks 11 are raised and their tips are aligned with the center of the insertion opening 65 in the height direction. Then, the vehicle body 19 is moved forward to insert the forks 11. At this time, no obstacles are detected within the detection distance SD in any of the diagonally upward direction 21U, the forward direction 21M, or the diagonally downward direction 21L of the sensor 20. The mutually opposing surfaces of the top plate 61 and bottom plate 62 of the pallet 60 are referred to as the top surface 61A and the bottom surface 62A, respectively.

[0021] If the top surface 61A and the bottom surface 62A are parallel to the direction of movement of the fork 11 during insertion, the fork 11 will not come into contact with the top surface 61A and the bottom surface 62A even if the insertion length of the fork 11 is increased. However, if the top surface 61A and the bottom surface 62A are inclined with respect to the direction of movement of the fork 11, the tip of the fork 11 may come into contact with the top surface 61A or the bottom surface 62A during the insertion operation.

[0022] Next, with reference to Figures 5A to 5C, the control of the fork 11 when the top surface 61A and bottom surface 62A are inclined with respect to the direction of movement of the fork 11 will be described. Figures 5A to 5C are schematic cross-sectional views showing the positional relationship between the pallet 60 and the fork 11 from the start of insertion of the fork 11 to during the insertion operation.

[0023] As shown in Figure 5A, the pallet 60 is tilted in a direction in which the top surface 61A and bottom surface 62A are lifted in the direction of movement of the fork 11. At the start of insertion, no obstacles are detected within the detection distance SD from the tip of the fork 11 in the diagonally upward direction 21U, the forward direction 21M, and the diagonally downward direction 21L.

[0024] As shown in Figure 5B, when the insertion length of the fork 11 increases, the bottom surface 62A enters within the detection distance SD of the diagonally downward direction 21L from the tip of the fork 11, and the bottom surface 62A is detected as an obstacle. If the fork 11 is moved forward in this state, there is a possibility that the tip of the fork 11 will come into contact with the bottom surface 62A. When an obstacle is detected in the diagonally downward direction 21L, the control unit 50 controls the tilt mechanism 13 to tilt the fork 11 upward as shown in Figure 5C. In Figure 5C, the position of the fork 11 before tilting is shown by a dashed line. The tilt angle should be set in advance based on the distance between the top surface 61A and the bottom surface 62A, the length and thickness of the fork 11, the detection distance SD of the sensor 20, etc., so that the tip of the fork 11 after tilting is located approximately in the center of the space between the top surface 61A and the bottom surface 62A.

[0025] When the fork 11 is tilted upward, obstacles are no longer detected in the diagonally downward direction 21L from the tip of the fork 11. This makes it possible to avoid contact with the bottom surface 62A of the fork 11.

[0026] Next, with reference to Figures 6A to 6E, the control of the fork 11 when the top surface 61A and bottom surface 62A are inclined in the opposite direction to the direction of movement of the fork 11 will be described. Figures 6A to 6E are schematic cross-sectional views showing the positional relationship between the pallet 60 and the fork 11 from the start of insertion to during insertion.

[0027] As shown in Figure 6A, the top surface 61A and the bottom surface 62A are inclined downwards in the direction of movement of the fork 11. At the start of insertion, no obstacles are detected within the detection distance SD in the diagonally upward direction 21U, the forward direction 21M, and the diagonally downward direction 21L from the tip of the fork 11.

[0028] As shown in Figure 6B, when the insertion length of the fork 11 increases, the top surface 61A enters within the detection distance SD in the diagonally upward direction 21U from the tip of the fork 11, and the top surface 61A is detected as an obstacle. If the fork 11 is moved forward in this state, there is a possibility that the tip of the fork 11 will come into contact with the top surface 61A. When an obstacle is detected in the diagonally upward direction 21U, the control unit 50 controls the tilt mechanism 13 to tilt the fork 11 downward as shown in Figure 6C. In Figure 6C, the position of the fork 11 before tilting is shown by a dashed line.

[0029] If the fork 11 is moved further forward in this state, as shown in Figure 6D, the top surface 61A will again enter within the detection distance SD in the diagonally upward direction 21U from the tip of the fork 11, and the top surface 61A will be detected again as an obstacle. In Figure 6D, the position of the fork 11 before moving forward is shown by a dashed line. When an obstacle is detected again in the diagonally upward direction 21U, the control unit 50 controls the tilt mechanism 13 to tilt the fork 11 further downward, as shown in Figure 6E. In Figure 6E, the position of the fork 11 before tilting again is shown by a dashed line. By tilting the fork 11 in this way, contact between the tip of the fork 11 and the top surface 61A can be avoided.

[0030] Next, with reference to Figure 7, the control performed by the control unit 50 (Figure 1) will be described. Figure 7 is a flowchart showing the control procedure performed by the control unit 50 during the insertion operation of the fork 11.

[0031] The control unit 50 controls the lifting mechanism 12 (Figure 1) to adjust the height of the fork 11 to match the height of the insertion opening 65 of the pallet 60 (Figure 3) (Step SA1). With the height of the fork 11 adjusted to the height of the insertion opening 65, the control unit 50 controls the motor 17 to start moving forward (starts the insertion operation of the fork 11) (Step SA2).

[0032] If an obstacle is detected diagonally downward 21L from the tip of the fork 11 (step SA3, Figure 5B), the control unit 50 controls the tilt mechanism 13 (Figure 1) to tilt the fork 11 upward (step SA4, Figure 5C). If an obstacle is detected diagonally upward 21U from the tip of the fork 11 (step SA5, Figures 6B, 6D), the control unit 50 controls the tilt mechanism 13 (Figure 1) to tilt the fork 11 downward (step SA6, Figures 6C, 6E).

[0033] The forward movement (insertion operation) of the fork 11 continues until the insertion length reaches the target insertion length (step SA7). While moving forward, obstacle detection and tilt control of the fork 11 are performed. When the insertion length of the fork 11 reaches the target insertion length, the control unit 50 stops the forward movement by controlling the motor 17 (step SA8).

[0034] Next, the excellent effects of the above embodiment will be described. In the above embodiment, as shown in Figures 5A and 6A, even when the top surface 61A and bottom surface 62A of the pallet 60 are inclined with respect to the direction of travel of the fork 11, it is possible to avoid the tip of the fork 11 contacting the top surface 61A and bottom surface 62A during the insertion operation of the fork 11. This helps to suppress cargo collapse and other issues.

[0035] Next, an automated guided transport forklift according to another embodiment will be described with reference to Figures 8A to 9. Hereafter, the description of components common to the automated guided transport forklift described with reference to Figures 1 to 7 will be omitted. In the embodiment described with reference to Figures 1 to 7, contact between the fork 11 and the pallet 60 is avoided during the insertion operation of the fork 11. In contrast, in this embodiment, the time required for the step SA1 shown in Figure 7, in which the height of the fork 11 is adjusted to match the height of the insertion opening 65 of the pallet 60, is shortened.

[0036] Figures 8A to 8E are schematic cross-sectional views showing the positional relationship between the forks 11 and the insertion opening 65 of the pallet 60 when the automated guided forklift according to this embodiment raises the forks 11. Figure 9 is a flowchart showing the control procedure when the automated guided forklift according to this embodiment raises the forks.

[0037] As shown in Figure 8A, in the initial state, the fork 11 is facing the pallet 60 and positioned lower than the insertion opening 65 of the pallet 60. The control unit 50 starts raising the fork 11 from this state (step SB1). When the fork 11 is raised, as shown in Figure 8B, the bottom plate 62 of the pallet 60 is detected within the detection distance SD of 21U diagonally upward from the tip of the fork 11 (step SB2). That is, the upward sensor 20U (Figure 2) enters an obstacle detection state. When the upward sensor 20U enters an obstacle detection state, the control unit 50 reduces the raising speed of the fork 11 (step SB3). Furthermore, it activates the obstacle detection process of the forward sensor 20M (step SB4). When the raising speed is reduced and the fork 11 is raised further, as shown in Figure 8C, the bottom plate 62 is removed from the area within the detection distance SD of 21U diagonally upward from the tip of the fork 11, and the upward sensor 20U (Figure 2) enters an obstacle non-detection state.

[0038] As the fork 11 is raised further, the bottom plate 62 is detected within the detection distance SD of 21M in the forward direction of the tip of the fork 11, as shown in Figure 8D (step SB5). That is, the forward direction sensor 20M (Figure 2) enters an obstacle detection state. Note that the forward direction sensor 20M may enter an obstacle detection state before the upward direction sensor 20U enters an obstacle non-detection state. As the fork 11 is raised further, the bottom plate 62 moves out of the area within the detection distance SD of 21M in the forward direction of the fork 11, as shown in Figure 8E, and the forward direction sensor 20M enters an obstacle non-detection state (step SB6).

[0039] After the front direction sensor 20M enters an obstacle detection state, the point at which it returns to an obstacle-free state corresponds to the height of the fork 11 matching the height of the top surface of the base plate 62 (the bottom surface of the insertion opening 65). From the point at which the front direction sensor 20M enters an obstacle-free state, the control unit 50 raises the fork 11 by a predetermined amount (step SB7) and stops it (step SB8).

[0040] The specified amount is set so that the fork 11 does not interfere with the bottom plate 62 of the pallet 60. For example, the specified amount should be set so that when the fork 11 is inserted into the insertion opening 65, a certain amount of gap, for example, 10 mm, is formed between the bottom surface of the fork 11 and the top surface of the bottom plate 62 (the bottom surface of the insertion opening 65). If the pallet 60 meets the specified specifications, when the fork 11 is raised by the specified amount from the moment the front direction sensor 20M does not detect any obstacles, the fork 11 can be inserted into the insertion opening 65 without interfering with the top plate 61 and bottom plate 62 of the pallet 60.

[0041] Next, the excellent effects of the above embodiment will be described. In the above embodiment, once no obstacle is detected in the diagonally upward direction 21U (Figure 8C), the upward speed of the fork 11 is reduced (step SB3). This improves the accuracy of the height alignment of the fork 11. Conversely, because the fork 11 is raised at a relatively fast speed until an obstacle is detected in the diagonally upward direction 21U, the time required to adjust the height of the fork 11 to the height of the insertion opening 65 can be shortened. This improves the efficiency of cargo handling operations.

[0042] Next, with reference to Figure 10, a modified example of the embodiment shown in Figures 8A to 9 will be described. Figure 10 is a flowchart showing the control procedure when an automated transport forklift raises its forks, according to a modified example of the embodiment shown in Figures 8A to 9.

[0043] The steps from step SB1 to step SB6 are the same as the steps from step SB1 to step SB6 shown in Figure 9. In this modified example, when the front direction sensor 20M does not detect an obstacle, the control unit 50 (Figure 1) stores the height of the bottom surface of the insertion opening 65, that is, the height of the fork 11 at the time the front direction sensor 20M did not detect an obstacle (step SC7).

[0044] As the fork 11 continues to rise, the front direction sensor 20M detects the top plate 61 of the pallet 60 and enters an obstacle detection state (step SC8). When the front direction sensor 20M enters the obstacle detection state, the control unit 50 stores the height of the ceiling of the insertion opening 65, that is, the height of the fork 11 at the time the front direction sensor 20M entered the obstacle detection state (step SC9).

[0045] The target height of the fork 11 is calculated from the height of the bottom surface and the height of the ceiling of the socket 65 (step SC10). The target height is preferably the average of the height of the bottom surface and the height of the ceiling of the socket 65. In other words, the height of the center of the socket 65 is preferably used as the target height of the fork 11. The control unit 50 then moves the fork 11 to the target height (step SC11).

[0046] Next, we will explain the superior effects of the modified example shown in Figure 10. In the embodiment shown in Figure 9, the target height of the fork 11 is set based only on the height of the bottom surface of the insertion opening 65. In contrast, in the modified example shown in Figure 10, the target height of the fork 11 is set based on the height of both the bottom surface and the top surface of the insertion opening 65. This increases the effectiveness of avoiding situations in which the fork 11 interferes with the bottom surface and top surface of the insertion opening 65.

[0047] Furthermore, the height dimension of the insertion opening 65 can be calculated from the heights of both the bottom and top of the insertion opening 65. From the height dimension of the insertion opening 65, it can be determined whether or not the pallet 60 meets the specifications. If the pallet 60 does not meet the specifications, the control unit 50 may stop the insertion operation of the fork 11. This prevents the fork 11 from interfering with the bottom or top of the insertion opening 65 before the insertion operation.

[0048] Next, other modifications of the embodiment shown in Figures 8A to 9 will be described. In the above embodiment, the upward speed is reduced (step SB3) when an obstacle is detected in the diagonally upward direction 21U (step SB2). Alternatively, the upward speed of the fork 11 may be reduced when an obstacle is detected in the diagonally upward direction 21U (step SB2), and then no further obstacles are detected in the diagonally upward direction 21U (Figure 8C).

[0049] In the above embodiment, when an obstacle is detected in the forward direction 21M (step SC1), and then when no further obstacles are detected in the forward direction 21M (step SC2), the raising of the forks 11 is stopped (step SC3). Alternatively, the raising of the forks 11 may be stopped when an obstacle is detected in the forward direction 21M (step SC1). In this case, the raising distance of the forks 11 from the time an obstacle is detected in the forward direction 21M should be set to a length equal to half the height dimension of the insertion opening 65 plus the thickness of the bottom plate 62 of the pallet 60.

[0050] The embodiments described above are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects and benefits from similar configurations in multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the embodiments described above. For example, it will be obvious to those skilled in the art that various modifications, improvements, and combinations are possible. [Explanation of Symbols]

[0051] 10. Automated Guided Forklift (AGF) 11 Forks 12 Lifting mechanism 13 Tilt mechanism 14 Fulcrum 15 Mast 17 Motor 18 wheels 19 car bodies 20 sensors 20L Downward Sensor 20M Front-facing sensor 20U Upward Sensor 21L diagonally downward 21M Front direction 21U Diagonal upward direction 30 Fork extension line 50 Control Unit 60 pallets 61 Top plate 61A Top surface 62 Bottom plate 62A Bottom 63 digits 65 outlets

Claims

1. A fork and A lifting mechanism for raising and lowering the fork, Sensors and, A control unit that controls the lifting mechanism based on the detection result of the sensor. Equipped with, The sensor detects obstacles diagonally above the straight line extending the fork, and obstacles on the straight line extending the fork. When the fork is positioned opposite the pallet and raised to the height of the pallet's insertion opening, The control unit, The fork is made to start rising, When the sensor detects an obstacle diagonally above, or when no obstacle is subsequently detected, the upward speed of the fork is reduced. A fork insertion and lifting device that stops the fork from rising when an obstacle is detected in the straight line extending from the fork, or when no obstacle is subsequently detected.

2. Furthermore, it is equipped with a tilt mechanism for tilting the fork, The sensor further detects obstacles diagonally downwards relative to the straight line extending the fork, The fork insertion and lifting device according to claim 1, wherein the control unit, when inserting the fork into the insertion opening of the pallet, tilts the fork upward when it detects an obstacle diagonally downward, and tilts the fork downward when it detects an obstacle diagonally upward.

3. The fork insertion lifting device according to claim 1 or 2, wherein the sensor is attached to the tip of the fork.

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