Crane load increase prevention device

Abstract

To provide a load increase prevention device for a crane, which can ensure prevention of the increase of a load applied on the crane.SOLUTION: The load increase prevention device for the crane comprises: an angle sensor that detects an attitude of the crane; a load sensor that detects an actual load of a suspending cargo suspended from the crane; a storage that stores a prescribed load which is a permissible value of the actual load for each attitude of the crane; and a controller that determines whether or not a load rate which is a rate of the actual load to the prescribed load increases when it is assumed that the attitude of the crane is changed to a virtual attitude slightly changed from a current attitude detected by an attitude detector.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a load increase prevention device for a crane, which prevents an increase in the load applied to the crane. [Background technology]

[0002] Patent Document 1 discloses an overload prevention device for a jib crane that is installed on a crane and prohibits the jib from being lowered or hoisted when the load exceeds a limit (overload state). In this overload prevention device, the first operation is to lower the jib, and in the event of an overload state, a control operation is performed that allows the jib to be raised. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-183592 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 allows for the reverse of the operation that occurred immediately before the crane stopped due to overload. However, the capacity of a crane is determined by a complex combination of a wide range of factors, including the strength of the attachments (boom, jib), the strength of the members that support the attachments (guy lines, struts, etc.), wind load characteristics, and stability. Therefore, performing the reverse operation described in Patent Document 1 may worsen the overload condition.

[0005] An object of the present invention is to provide a load increase prevention device for a crane that can reliably prevent an increase in the load applied to the crane. [Means for solving the problem]

[0006] The present invention is characterized by comprising an attitude detection device that detects the attitude of a crane, an actual load detection device that detects the actual load of a load suspended by the crane, a storage device that stores a predetermined load that is an allowable value of the actual load for each attitude of the crane, and a determination means that determines whether or not a load factor, which is the ratio of the actual load to the predetermined load, will increase when it is assumed that the attitude of the crane is changed to a virtual attitude that is a slight change from the current attitude detected by the attitude detection device. [Effects of the Invention]

[0007] According to the present invention, it is determined whether the load factor will increase if the crane's attitude is changed to a virtual attitude that is a slight change from the current attitude detected by the attitude detection device. The capacity of a crane is determined by a complex combination of a wide range of factors, including the strength of the attachment (e.g., boom, jib), the strength of the members supporting the attachment (e.g., guy lines, struts, etc.), wind load characteristics, and stability. Therefore, an operation that has conventionally been set as a safe operation in an overload prevention device (e.g., an operation to reduce the working radius) may actually be a dangerous operation. Therefore, it is determined whether the load factor will increase if the crane's attitude is changed to a virtual attitude without actually changing the crane's attitude. This makes it possible to determine whether an operation that changes the crane's attitude to the virtual attitude is a safe operation. Therefore, compared to when, for example, an operation to reduce the working radius is uniformly set as a safe operation, it is possible to accurately determine whether an operation that changes the crane's attitude is a safe operation. This reliably prevents an increase in the load on the crane. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of a crane. [Figure 2] FIG. 2 is a circuit diagram of a load increase prevention device. [Figure 3A] This is a diagram showing the relationship between working radius (m) and lifting capacity (t). [Figure 3B]FIG. 1 is a diagram showing the relationship between the jib offset angle (°) and the lifting capacity (t). [Figure 4] FIG. 10 is an explanatory diagram of a determination made by a controller. [Figure 5] 1 is a graph showing the relationship between the boom hoisting angle, the jib offset angle, and the load factor. [Figure 6] 1 is a graph showing the relationship between the boom hoisting angle, the jib offset angle, and the load factor, with a boundary line indicating the crane's working radius superimposed. [Figure 7] This is a diagram showing three graphs side by side. [Figure 8] FIG. 1 is a diagram illustrating a three-dimensional graph. [Figure 9] 10 is a flowchart of a motion determination process. [Figure 10] 10 is a flowchart of the operation determination process, which is a continuation of FIG. 9. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0010] (Crane configuration) The crane load increase prevention device (load increase prevention device) in this embodiment prevents an increase in the load on the crane. As shown in FIG. 1, which is a side view of a crane 10, the crane 10 is a luffing crane, with an upper rotating body 12 rotatably mounted (attached) to the top of a crawler-type lower traveling body 11. Note that the crane 10 may be a mobile crane using a moving means other than crawlers (e.g., wheels), or a fixed crane without a moving means. Note that the application of the present invention is not limited to luffing cranes. For example, the present invention can also be applied to tower cranes and general cranes that only have a boom but no jib or struts. Booms, jibs, and struts will be described later. The present invention can also be applied to cranes that have a lifting section such as a box boom (telescopic boom) or a shovel arm instead of a lattice boom.

[0011] As shown in Figure 1, crane 10 includes an upper rotating body 12, a lower running body 11 that rotatably supports upper rotating body 12 via a rotating device 50, a hoisting member including a boom 14 and a jib 15, and a mast 16 that is a boom hoisting member. A counterweight 17 is mounted on the rear of upper rotating body 12 to adjust the balance of crane 10. A cab 13 is provided at the front end of upper rotating body 12. Cab 13 corresponds to the driver's seat of crane 10.

[0012] The boom 14 is a so-called lattice type and is formed by connecting multiple unit booms (unit members). Specifically, the boom 14 is composed of a lower boom 14A, one or more (two in the illustrated example) intermediate booms 14B, and an upper boom 14C. The lower boom 14A is connected to the front of the upper rotating structure 12 so as to be rotatable in the hoisting direction. The intermediate boom 14B is detachably attached to the tip of the lower boom 14A. The upper boom 14C is detachably attached to the tip of the intermediate boom 14B. A rear strut 18 and a front strut 19 for rotating the jib 15, as described below, are rotatably connected to the tip of this upper boom 14C. The boom 14 is rotatably supported on the upper rotating structure 12 with a boom foot pin 14s provided at the lower end as a fulcrum.

[0013] However, the present invention is not limited to a specific structure of the boom 14. For example, the boom 14 may not have an intermediate boom 14B, or may have a different number of intermediate booms 14B than the above. Furthermore, the boom 14 may be formed from a single member.

[0014] The jib 15 is also a so-called lattice type, and is formed by connecting multiple unit jibs (unit members). Specifically, the jib 15 is composed of a lower jib 15A, one or multiple (one in the illustrated example) intermediate jibs 15B, and an upper jib 15C. The lower jib 15A is connected to the tip of the upper boom 14C so that it can rotate in the hoisting direction. The intermediate jib 15B is detachably attached to the tip of the lower jib 15A. The upper jib 15C is detachably attached to the tip of the intermediate jib 15B. The rotation center axis of the jib 15 is a horizontal axis parallel to the rotation center axis (boom foot pin 14s) of the boom 14 relative to the upper rotating body 12. The jib 15 is detachable from the boom 14.

[0015] The mast 16 has a base end and a pivoting end, and the base end is pivotally connected to the upper rotating body 12. The pivoting axis of the mast 16 is parallel to the pivoting axis of the boom 14 and is located immediately rearward of the pivoting axis of the boom 14. In other words, the mast 16 is pivotable in the same direction as the boom 14 is raised and lowered. Meanwhile, the pivoting end of the mast 16 is connected to the tip of the boom 14 via a pair of boom guy lines 20 on the left and right. This connection coordinates the rotation of the mast 16 and the rotation of the boom 14.

[0016] A pair of left and right backstops 21 are provided on the upper rotating body 12. These backstops 21 come into contact with the left and right sides of the lower boom 14A of the boom 14 when the boom 14 reaches the upright position shown in FIG. 1. This contact prevents the boom 14 from being blown backward by strong winds, etc. The left-right direction is the direction perpendicular to the plane of the paper in FIG. 1.

[0017] The rear strut 18 and the front strut 19 are pivotally supported at the tip of the boom 14. The rear strut 18 and the front strut 19 are detachably attached to the upper boom 14C. The rear strut 18 is held in a position in which it extends from the tip of the upper boom 14C toward the boom-raising side (left side in FIG. 1 ). To maintain this position, a pair of left and right backstops 22 and a pair of left and right strut guy links 23 are interposed between the rear strut 18 and the boom 14. The backstops 22 are interposed between the upper boom 14C and the intermediate portion of the rear strut 18, supporting the rear strut 18 from below. The strut guy link 23 is tensioned to connect the tip of the rear strut 18 to the lower boom part 14A of the boom 14, and its tension regulates the position of the rear strut 18. The strut guy link 23 is composed of multiple guy links connected together.

[0018] The rear strut 18 and the front strut 19 may be rotatably supported at the base end of the jib 15. Alternatively, the rear strut 18 may be rotatably supported at the tip of the boom 14, and the front strut 19 may be rotatably supported at the base end of the jib 15.

[0019] The front struts 19 are connected to the jib 15 so as to rotate in conjunction with (integrally with) the jib 15. More specifically, a pair of left and right jib guy lines 24 are tensioned to connect the tip of the front strut 19 with the tip of the jib 15. Therefore, the jib 15 is raised and lowered by the rotational drive of the front struts 19. The aforementioned rear struts 18 are disposed behind the front struts 19 as shown in FIG. 1, and form a substantially isosceles triangle shape with the front struts 19.

[0020] The crane 10 is equipped with various winches 49. Specifically, a boom hoist winch 25 for raising and lowering the boom 14, a jib hoist winch 26 for rotating the jib 15 in the hoisting direction, and a main hoist winch 27 and an auxiliary hoist winch 28 for hoisting and lowering a load are installed. In the crane 10 according to this embodiment, the boom hoist winch 25 is installed near the base end of the mast 16. The jib hoist winch 26, main hoist winch 27, and auxiliary hoist winch 28 are all installed on the lower boom section 14A of the boom 14. These winches 25, 26, 27, and 28 may also be mounted on the upper rotating body 12.

[0021] The boom hoist winch 25 winds in and pays out the boom hoist rope 29. The boom hoist rope 29 is laid out so that this winding and paying out causes the mast 16 to rotate. Specifically, sheave blocks 30, 31, each with a plurality of sheaves arranged in the width direction, are provided at the rotating end of the mast 16 and the rear end of the upper rotating body 12, and the boom hoist rope 29 pulled out from the boom hoist winch 25 is stretched between the sheave blocks 30, 31. Therefore, when the boom hoist winch 25 winds in and pays out the boom hoist rope 29, the distance between the two sheave blocks 30, 31 changes, causing the mast 16, and further the boom 14, which is linked to it, to rotate in the hoisting direction.

[0022] The jib hoist winch 26 winds in and pays out the jib hoist rope 32 wound between the rear strut 18 and the front strut 19. The jib hoist rope 32 is routed so that the front strut 19 rotates as the rope is wound in and out. Specifically, a guide sheave 33 is provided on the upper boom 14C of the boom 14, and sheave blocks 34, 35, each having a plurality of sheaves arranged in the width direction, are provided at the rotating end of the rear strut 18 and the rotating end of the front strut 19. The jib hoist rope 32 pulled out from the jib hoist winch 26 is hung on the guide sheave 33 and stretched between the sheave blocks 34, 35. Therefore, winding or unwinding the jib hoist rope 32 by the jib hoist winch 26 changes the distance between the two sheave blocks 34, 35, causing the front strut 19 and, further, the jib 15 linked thereto to rotate in the hoisting direction.

[0023] The main hoisting winch 27 hoists and lowers a load using a main hoisting rope 36. For this main hoisting, main hoisting guide sheaves 37, 38, and 39 are rotatably mounted near the base end of the rear strut 18, near the base end of the front strut 19, and at the tip of the jib 15, respectively, and a main hoisting sheave block is provided adjacent to the main hoisting guide sheave 39, with multiple main hoisting point sheaves 40 arranged in the width direction. The main hoisting rope 36 pulled out from the main hoisting winch 27 is looped around the main hoisting guide sheaves 37, 38, and 39 in order, and is stretched between the main hoisting point sheave 40 of the sheave block and a sheave 42 of a sheave block mounted on a main load hook 41. Therefore, when the main hoisting winch 27 winds or unwinds the main hoisting rope 36, the distance between the two sheaves 40, 42 changes, and the main hook 41 connected to the main hoisting rope 36 hanging down from the tip of the jib 15 is wound up or lowered.

[0024] Similarly, the auxiliary winch 28 hoists and lowers a load using an auxiliary hoisting rope 43. For this auxiliary hoisting, auxiliary guide sheaves 44, 45, and 46 are rotatably mounted coaxially with the main hoisting guide sheaves 37, 38, and 39, respectively, and an auxiliary hoisting point sheave 47 is rotatably mounted adjacent to the auxiliary hoisting guide sheave 46. The auxiliary hoisting rope 43 pulled out from the auxiliary hoisting winch 28 is hung around the auxiliary hoisting guide sheaves 44, 45, and 46 in that order and suspended from the auxiliary hoisting point sheave 47. Therefore, when the auxiliary hoisting winch 28 winds or unwinds the auxiliary hoisting rope 43, an auxiliary hook 48 for the load, which is connected to the end of the auxiliary hoisting rope 43, is wound up or lowered.

[0025] (Circuit configuration of load increase prevention device) 2, which is a circuit diagram of the load increase prevention device 1, the load increase prevention device 1 has an angle sensor 2, a load sensor 3, a storage device 4, and a controller 5. The controller 5 controls the winch 49 and the swing device 50.

[0026] The angle sensor (posture detection device) 2 detects the posture of the crane 10. The angle sensor 2 has a boom angle sensor, a jib angle sensor, and a slewing angle sensor. The boom angle sensor is attached to the base end of the boom 14 and detects the hoisting angle of the boom 14. The hoisting angle of the boom 14 is the angle between the longitudinal center line of the boom 14 and the horizontal plane. The jib angle sensor is attached to the base end of the jib 15 and detects the offset angle of the jib 15. The offset angle of the jib 15 is the angle between the longitudinal center line of the boom 14 and the longitudinal center line of the jib 15. The slewing angle sensor detects the slewing angle of the upper slewing body 12 relative to the lower running body 11. For example, the slewing angle of the upper slewing body 12 is set to 0° when the front of the upper slewing body 12 is aligned with the front of the lower running body 11.

[0027] The sensor for detecting the attitude of the crane 10 is not limited to the angle sensor 2. For example, in the case of a crane with a telescopic boom, a measuring instrument for measuring the length of the boom may be provided.

[0028] The load sensor (actual load detection device) 3 detects the actual load of the load suspended from the jib 15. The load sensor 3 detects, for example, the tension applied to the main hoisting rope 36, and detects the actual load of the load from the detected tension.

[0029] The storage device 4 stores a rated load (predetermined load), which is an allowable value for the actual load of the suspended load, for each posture of the crane 10. The rated load is a load that can be lifted in advance for each posture of the crane 10. The predetermined load stored in the storage device 4 is not limited to the rated load, and may be a load greater than or less than the rated load. Here, the posture of the crane 10 changes depending on the elevation of the boom 14. The posture of the crane 10 also changes depending on the elevation of the jib 15. The posture of the crane 10 also changes depending on the rotation of the upper rotating body 12.

[0030] The controller 5 calculates a load factor, which is the ratio of the actual load to the rated load. If the load factor exceeds 100%, the crane 10 will be in an overload state.

[0031] The capacity of the crane 10 is determined by a complex combination of a wide range of factors, including the strength of the boom 14, the strength of the jib 15, the strength of the members supporting the boom 14 and jib 15 (boom guy lines 20, jib guy lines 24, rear struts 18, front struts 19, etc.), wind load characteristics, and stability. Therefore, an operation that has traditionally been set as a safe operation in an overload prevention device (for example, an operation to reduce the working radius) may actually be a dangerous operation. Here, a safe operation is an operation in the direction of reducing the load factor, and a dangerous operation is an operation in the direction of increasing the load factor.

[0032] For example, as shown in Figure 3A, which shows the relationship between the working radius (m) and the lifting capacity (t), and Figure 3B, which shows the relationship between the offset angle (°) of the jib 15 and the lifting capacity (t), if the hoisting angle of the boom 14 is changed from 70° to 80° while keeping the offset angle of the jib 15 constant, the working radius will decrease and the lifting capacity will increase (the load factor will decrease). This operation is on the safe side. However, if the hoisting angle of the boom 14 is then changed from 80° to 90°, the working radius will become even smaller, but the lifting capacity will also decrease (the load factor will increase). This operation is on the dangerous side.

[0033] In such cases, it is common to reduce the lifting capacity when the hoisting angle is 80° to prevent the lifting capacity from being reversed. However, it is not a good idea to cut off the range of lifting capacity that can actually be achieved.

[0034] Therefore, the controller (determination means) 5 determines whether the load factor will increase when it is assumed that the attitude of the crane 10 is changed to a virtual attitude that is slightly changed from the current attitude detected by the angle sensor 2. As described above, the attitude of the crane 10 changes due to the raising and lowering of the boom 14. The attitude of the crane 10 also changes due to the raising and lowering of the jib 15. The attitude of the crane 10 also changes due to the rotation of the upper rotating body 12.

[0035] As shown in Fig. 4, which is an explanatory diagram of the determination by the controller 5, the controller 5 first determines whether or not the load factor will increase when it is assumed that the attitude of the boom 14 is changed from the current attitude to a virtual attitude that is slightly raised. In the example shown in Fig. 4, the load factor increases in this case. Therefore, the controller 5 determines that this attitude change is a dangerous operation.

[0036] Next, the controller 5 determines whether the load factor will increase if the attitude of the boom 14 is assumed to be changed from the current attitude to a virtual attitude in which the boom 14 is slightly tilted. In the example shown in Fig. 4, the load factor will increase in this case. Therefore, the controller 5 determines that this attitude change is a dangerous operation.

[0037] Next, the controller 5 determines whether the load factor will increase if the posture of the jib 15 is assumed to be slightly changed from the current posture to a virtual posture. In the example shown in Fig. 4, the load factor will decrease in this case. Therefore, the controller 5 determines that this posture change is a safe operation.

[0038] Next, the controller 5 determines whether the load factor will increase if the posture of the jib 15 is assumed to be changed from the current posture to a virtual posture in which the posture is slightly tilted. In the example shown in Fig. 4, the load factor will increase in this case. Therefore, the controller 5 determines that this posture change is a dangerous operation.

[0039] Next, the controller 5 determines whether the load factor will increase if the upper rotating body 12 is assumed to be changed from its current posture to a virtual posture in which it is slightly rotated to the right. In the example shown in Fig. 4, the load factor will decrease in this case. Therefore, the controller 5 determines that this posture change is a safe operation.

[0040] Next, the controller 5 determines whether the load factor will increase if the upper rotating body 12 is assumed to be changed from its current posture to a virtual posture in which it is slightly rotated left. In the example shown in Fig. 4, the load factor will increase in this case. Therefore, the controller 5 determines that this posture change is a dangerous operation.

[0041] The controller (restriction means) 5 restricts the operation of changing the attitude of the crane 10 to the virtual attitude when it determines that the load factor is increasing and the actual load will exceed the rated load. On the other hand, the controller (allowance means) 5 allows the operation of changing the attitude of the crane 10 to the virtual attitude when it determines that the load factor is decreasing. In the example shown in FIG. 4, the operation of raising the boom 14, the operation of lowering the boom 14, the operation of lowering the jib 15, and the operation of rotating the upper rotating body 12 to the left are restricted as dangerous operations. On the other hand, in the example shown in FIG. 4, the operation of raising the jib 15 and the operation of rotating the upper rotating body 12 to the right are allowed as safe operations.

[0042] Here, the controller (stopping means) 5 stops the operation of the crane 10 when the actual load exceeds the rated load (when an overload state occurs). In this embodiment, the above determination is made when the crane 10 is stopped, and is not made at any time other than when the crane 10 is stopped. Note that the above determination may be made at all times while the crane 10 is in operation.

[0043] As described above, it is determined whether the load factor will increase when the attitude of the crane 10 is assumed to be changed to a virtual attitude without actually changing the attitude of the crane 10. This makes it possible to determine whether the operation of changing the attitude of the crane 10 to the virtual attitude is a safe operation. Therefore, compared to when, for example, an operation of reducing the working radius is uniformly set as a safe operation, it is possible to accurately determine whether the operation of changing the attitude of the crane 10 is a safe operation. This makes it possible to reliably prevent the load on the crane 10 from increasing.

[0044] The above determination can be made by extending a conventional overload determination algorithm, and since the calculation load is small, it can be implemented without making major changes to a conventional overload prevention device.

[0045] Furthermore, if it is determined that changing the attitude of the crane 10 to the virtual attitude would increase the load factor and cause the actual load to exceed the rated load, the operation of changing the attitude of the crane 10 to the virtual attitude is restricted. On the other hand, if it is determined that changing the attitude of the crane 10 to the virtual attitude would decrease the load factor, the operation of changing the attitude of the crane 10 to the virtual attitude is permitted. By restricting the operation of changing the attitude of the crane 10 to the virtual attitude when the load factor increases, it is possible to suitably prevent the load on the crane 10 from increasing.

[0046] Furthermore, a determination is made as to whether the load factor is increasing when the crane 10 is stopped. By making the determination only when the crane 10 is stopped, rather than making the determination constantly while the crane 10 is in operation, the load required for the determination can be reduced and the time required for the determination can be shortened.

[0047] Returning to FIG. 2, the load increase prevention device 1 has a display 6. The controller 5 displays a diagram showing its own determination result superimposed on a diagram showing the posture of the crane 10 on the display (graphic display device) 6. That is, as shown in FIG. 4, the display 6 displays a diagram 60 showing the posture of the crane 10 superimposed on a diagram 61 showing the determination result by the controller 5. The diagram 61 showing the determination result indicates a safe operation with "OK" and a dangerous operation with "NG".

[0048] The operator of the crane 10 can recognize safe operation and dangerous operation by looking at the display 6. Therefore, the operator can operate the crane 10 carefully so as not to increase the load on the crane 10.

[0049] The graphs shown in Figures 5 and 6 show the change in load factor relative to changes in the attitude of the crane 10. The graphs shown in Figures 5 and 6 show the relationship between the boom 14 hoisting angle (°), the jib 15 offset angle (°), and the load factor, with three load factor ranges (0-80%, 80-100%, and 100% or more) color-coded. Furthermore, the graph shown in Figure 6 displays a superimposed boundary line (line) L indicating the working radius of the crane 10. The boundary line L is set for each of a plurality of working radii.

[0050] The controller 5 causes the display (graph display device) 6 to display the graphs shown in FIG. 5 or FIG. 6 in place of the display shown in FIG. 4 or switchably with the display shown in FIG.

[0051] In a configuration in which constant judgment is performed while the crane 10 is in operation, the current posture P changes from moment to moment, as shown in Figures 5 and 6. Note that, if judgment is performed while the crane 10 is stopped, the current posture P is located on the line indicating a load factor of 100%. In the example shown in Figure 5, it can be seen that, in the current posture P, increasing or decreasing the hoisting angle of the boom 14 while keeping the offset angle of the jib 15 the same increases the load factor. Also, in the example shown in Figure 5, it can be seen that, in the current posture P, increasing the offset angle of the jib 15 while keeping the hoisting angle of the boom 14 the same increases the load factor, whereas decreasing the offset angle of the jib 15 while keeping the hoisting angle of the boom 14 the same decreases the load factor.

[0052] Also, in the example shown in Figure 6, if the hoisting angle of the boom 14 is increased while the offset angle of the jib 15 remains the same in the current position P, the working radius of the crane 10 decreases and the load factor increases, whereas if the hoisting angle of the boom 14 is decreased while the offset angle of the jib 15 remains the same, the working radius of the crane 10 increases and the load factor decreases. Also, in the example shown in Figure 6, if the hoisting angle of the boom 14 is increased while the offset angle of the jib 15 remains the same in the current position P, the working radius of the crane 10 increases but the load factor increases, whereas if the hoisting angle of the boom 14 is decreased while the offset angle of the jib 15 remains the same, the working radius of the crane 10 decreases and the load factor decreases.

[0053] By viewing the display 6, the operator can recognize the current load factor, allowing for careful operation so as not to increase the load on the crane 10. Specifically, humans tend to perceive an increase in the load factor as the working radius of the crane 10 increases. However, as shown in the example of FIG. 6, if the boom hoisting angle is reduced while the offset angle of the jib 15 remains the same in the current position P, the load factor decreases despite the working radius of the crane 10 increasing. Similarly, humans tend to perceive a decrease in the load factor as the working radius of the crane 10 decreases. However, as shown in the example of FIG. 6, if the boom hoisting angle is increased while the offset angle of the jib 15 remains the same in the current position P, the load factor increases despite the working radius of the crane 10 decreasing. In this way, an operation pattern occurs in which the increase or decrease in the load factor due to the actual behavior of the boom 14 and jib 15 does not match the increase or decrease in the load factor intuitively perceived by the operator. However, by checking the load rate on the display 6 while operating the device, the operator can prevent unexpected operation restrictions (overload state) from occurring due to a discrepancy between the operator's sense and the actual increase or decrease in the load rate.

[0054] Furthermore, crane operations generally require operations to carry a suspended load farther. By recognizing the boundary line L indicating the working radius, the operator can determine whether or not the working radius of the crane 10 can be increased by operating on the safe side.

[0055] (Variation) As shown in Fig. 7, which shows three graphs displayed side by side, the display 6 may display graphs showing changes in load factor with changes in the attitude of each of multiple parts of the crane 10 that contribute to changes in the attitude of the crane 10, side by side or by switching between them. Here, the crane 10 corresponding to Fig. 7 is not the luffing crane shown in Fig. 1, but a crane in which the length of the boom 14 is extendable. In addition, the multiple parts of the crane 10 that contribute to changes in the attitude of the crane 10 are the boom 14, jib 15, and upper rotating body 12 in the above example.

[0056] The graph on the left side of Fig. 7 shows the relationship between the length (m) of the boom 14, the boom 14 hoisting angle (°), and the load factor. The graph in the center of Fig. 7 shows the relationship between the rotation angle (°) of the upper rotating body 12, the offset angle (°) of the jib 15, and the load factor. The graph on the right side of Fig. 7 shows the relationship between the working radius (m) of the crane 10, the lifting capacity (t) of the crane 10, and the load factor.

[0057] By displaying the graphs for a plurality of parts side by side or by switching between them, the operator of the crane 10 can easily recognize which operations are on the safe side.

[0058] 8, which is a diagram showing a three-dimensional graph, the display 6 may display a three-dimensional graph of the change in load factor relative to the change in attitude at each of multiple parts of the crane 10 that contribute to the change in attitude of the crane 10. The three-dimensional graph in FIG. 8 shows the relationship between the boom 14 hoisting angle (°), the jib 15 offset angle (°), the lifting capacity (t) of the crane 10, and the load factor.

[0059] By displaying the change in load factor in response to the change in posture at each of the multiple parts of the crane 10 as a three-dimensional graph, the operator of the crane 10 can easily recognize what operations are on the safe side.

[0060] Furthermore, instead of the controller 5 making a judgment each time the attitude of the crane 10 changes, the controller 5 or an external computer may make a judgment in advance, and the controller (storage control means) 5 may store the judgment result in advance in the storage device 4 in association with the attitude of the crane 10. There is a one-to-one correspondence between the attitude of the crane 10 and the safe operation and the dangerous operation. Therefore, when the crane 10 assumes a certain attitude, the safe operation and the dangerous operation corresponding to that attitude are known. The judgment result may also be linked to the rated load.

[0061] In this case, the controller 5 reads out the determination result corresponding to the current attitude of the crane 10 from the storage device 4. Then, if the determination result corresponding to the current attitude of the crane 10 is that the load factor is increasing and the actual load exceeds the rated load, the controller 5 restricts the operation of changing the attitude of the crane 10 to the virtual attitude. On the other hand, if the determination result corresponding to the current attitude of the crane 10 is that the load factor is decreasing, the controller 5 allows the operation of changing the attitude of the crane 10 to the virtual attitude.

[0062] Since the judgment result is previously associated with the attitude of the crane 10, it is not necessary to make a judgment every time the attitude of the crane 10 is changed. This reduces the load required for judgment and shortens the time required for judgment.

[0063] (Operation of the load increase prevention device) Next, the operation of the load increase prevention device 1 will be described with reference to FIGS. 9 and 10, which are flowcharts of the operation determination process.

[0064] First, the controller 5 determines whether or not the crane 10 is in an overload state (step S1). If it is determined in step S1 that the crane 10 is not in an overload state (S1: NO), the controller 5 returns to step S1. On the other hand, if it is determined in step S1 that the crane 10 is in an overload state (S1: YES), the controller 5 stops the operation of the crane 10 (step S2).

[0065] Next, the controller 5 assumes that the attitude of the boom 14 has been changed to a virtual attitude that is slightly raised from the current attitude (step S3). Then, the controller 5 determines whether or not the load factor will increase in this case (step S4). If the load factor increases in step S4 (S4: YES), the controller 5 sets this attitude change as a dangerous operation (step S5). On the other hand, if the load factor does not increase in step S4 (S4: NO), the controller 5 sets this attitude change as a safe operation (step S6).

[0066] Next, the controller 5 assumes that the attitude of the boom 14 has been changed from the current attitude to a virtual attitude that is slightly tilted (step S7). Then, the controller 5 determines whether or not the load factor will increase in this case (step S8). If the load factor increases in step S8 (S8: YES), the controller 5 sets this attitude change as a dangerous operation (step S9). On the other hand, if the load factor does not increase in step S8 (S8: NO), the controller 5 sets this attitude change as a safe operation (step S10).

[0067] Next, the controller 5 assumes that the posture of the jib 15 has been changed to a virtual posture that is slightly raised from the current posture (step S11). Then, the controller 5 determines whether or not the load factor increases in this case (step S12). If the load factor increases in step S12 (S12: YES), the controller 5 sets this posture change as a dangerous operation (step S13). On the other hand, if the load factor does not increase in step S12 (S12: NO), the controller 5 sets this posture change as a safe operation (step S14).

[0068] Next, the controller 5 assumes that the posture of the jib 15 has been changed from the current posture to a virtual posture that is slightly tilted (step S15). Then, the controller 5 determines whether or not the load factor increases in this case (step S16). If the load factor increases in step S16 (S16: YES), the controller 5 sets this posture change as a dangerous operation (step S17). On the other hand, if the load factor does not increase in step S16 (S16: NO), the controller 5 sets this posture change as a safe operation (step S18).

[0069] Next, the controller 5 assumes that the attitude of the upper rotating body 12 has been changed from the current attitude to a virtual attitude that is slightly rotated to the right (step S19). Then, the controller 5 determines whether or not the load factor will increase in this case (step S20). If the load factor increases in step S20 (S20: YES), the controller 5 sets this attitude change as a dangerous operation (step S21). On the other hand, if the load factor does not increase in step S20 (S20: NO), the controller 5 sets this attitude change as a safe operation (step S22).

[0070] Next, the controller 5 assumes that the attitude of the upper rotating body 12 has been changed from the current attitude to a virtual attitude that is slightly rotated to the left (step S23). Then, the controller 5 determines whether or not the load factor will increase in this case (step S24). If the load factor increases in step S24 (S24: YES), the controller 5 sets this attitude change as a dangerous operation (step S25). On the other hand, if the load factor does not increase in step S24 (S24: NO), the controller 5 sets this attitude change as a safe operation (step S26).

[0071] Next, the controller 5 restricts the dangerous operation (step S27). Also, the controller 5 allows the safe operation (step S28). Then, the controller 5 causes the display 6 to display a display showing the determination result (step S29), and ends this flow.

[0072] (effect) As described above, the load increase prevention device 1 according to this embodiment determines whether the load factor would increase if the crane 10 were to change its attitude to a virtual attitude that is a slight change from the current attitude detected by the angle sensor 2. The capacity of the crane 10 is determined by a complex combination of a wide range of factors, including the strength of the attachment (e.g., the boom 14 and jib 15), the strength of the members supporting the attachment (e.g., the boom guy line 20, the jib guy line 24, the rear strut 18, and the front strut 19), wind load characteristics, and stability. Therefore, an operation that has been set as a safe operation in a conventional overload prevention device (e.g., an operation to reduce the working radius) may actually be a dangerous operation. Therefore, the device determines whether the load factor would increase if the attitude of the crane 10 were to change to the virtual attitude without actually changing the attitude of the crane 10. This makes it possible to determine whether the operation of changing the attitude of the crane 10 to the virtual attitude is a safe operation. Therefore, compared to when, for example, an operation to reduce the working radius is uniformly set as a safe operation, it is possible to accurately determine whether an operation to change the attitude of the crane 10 is a safe operation. This makes it possible to reliably prevent the load on the crane 10 from increasing.

[0073] Furthermore, when it is determined that changing the attitude of the crane 10 to the virtual attitude would increase the load factor and cause the actual load to exceed the rated load, the operation of changing the attitude of the crane 10 to the virtual attitude is restricted. On the other hand, when it is determined that changing the attitude of the crane 10 to the virtual attitude would cause the load factor to decrease, the operation of changing the attitude of the crane 10 to the virtual attitude is permitted. By restricting the operation of changing the attitude of the crane 10 to the virtual attitude when the load factor increases and causes the actual load to exceed the rated load, an increase in the load applied to the crane 10 can be suitably prevented.

[0074] Furthermore, a determination is made as to whether the load factor is increasing when the crane 10 is stopped. If the determination is made only when the crane 10 is stopped, rather than constantly while the crane 10 is in operation, the load required for the determination can be reduced, and the time required for the determination can be shortened.

[0075] 4, a diagram 61 showing the determination result by the controller 5 is superimposed on a diagram 60 simulating the posture of the crane 10 and displayed on the display 6. Therefore, the operator of the crane 10 can recognize safe operation and dangerous operation by looking at the display 6. Therefore, the operator can perform careful operation so as not to increase the load on the crane 10.

[0076] 5 and 6, the change in load factor relative to the change in attitude of the crane 10 is graphed and displayed on the display 6. Therefore, the operator of the crane 10 can recognize safe and dangerous operations by looking at the display 6. Furthermore, by looking at the display 6, the operator can recognize the current load factor, and therefore can operate the crane 10 carefully so as not to increase the load on the crane 10.

[0077] Also, as shown in Figure 6, a boundary line L indicating the working radius of the crane 10 is displayed superimposed on the graph. Generally, crane operation requires operations to carry a suspended load farther. By recognizing the boundary line L indicating the working radius, the operator can determine whether or not the working radius of the crane 10 can be increased by operating on the safe side.

[0078] 7, graphs showing changes in load factor relative to changes in the attitude of each of a plurality of parts of the crane 10 that contribute to changes in the attitude of the crane 10 are displayed side by side or in a switchable manner on the display 6. By displaying graphs for each of a plurality of parts of the crane 10 that contribute to changes in the attitude of the crane 10 side by side or in a switchable manner, the operator of the crane 10 can easily recognize what operations are on the safe side.

[0079] 8, in a modified example, the change in load factor relative to the change in attitude at each of the multiple parts of the crane 10 that contribute to the change in attitude of the crane 10 is plotted as a three-dimensional graph and displayed on the display 6. By displaying the change in load factor relative to the change in attitude at each of the multiple parts of the crane 10 that contribute to the change in attitude of the crane 10 as a three-dimensional graph, the operator of the crane 10 can easily recognize what kind of operation is on the safe side.

[0080] In a modified example, the determination result by the controller 5 is associated with the attitude of the crane 10 and stored in the storage device 4. When the determination result corresponding to the current attitude of the crane 10 indicates that the load factor is increasing and the actual load exceeds the rated load, the operation of changing the attitude of the crane 10 to the virtual attitude is restricted. On the other hand, when the determination result corresponding to the current attitude of the crane 10 indicates that the load factor is decreasing, the operation of changing the attitude of the crane 10 to the virtual attitude is permitted. By restricting the operation of changing the attitude of the crane 10 to the virtual attitude when the load factor is increasing and the actual load exceeds the rated load, an increase in the load on the crane 10 can be suitably prevented. Furthermore, because the determination result is associated with the attitude of the crane 10 in advance, it is not necessary to make a determination each time the attitude of the crane 10 is changed. This reduces the load required for the determination and shortens the time required for the determination.

[0081] Although the embodiments of the present invention have been described above, they are merely illustrative examples and do not limit the present invention, and the specific configurations and other aspects can be appropriately modified in design. Furthermore, the actions and effects described in the embodiments of the invention are merely a list of the most preferred actions and effects resulting from the present invention, and the actions and effects of the present invention are not limited to those described in the embodiments of the present invention.

[0082] For example, in this embodiment, the rated load is used as the allowable value of the actual load, but for example, in an inspection, a load larger than the rated load may be used as the allowable value of the actual load. Also, at the site, as a safety measure, a load smaller than the rated load (for example, a load that is 80% of the rated load) may be used as the allowable value of the actual load.

[0083] Furthermore, in this embodiment, it is determined whether the load rate will increase from an overload state, but it may also be determined whether the load rate will increase from a predetermined load state. Here, the predetermined load state may be a state in which a load smaller than the overload state (for example, a load with a load rate of 80%) is applied to the crane 10. In this case, it may be determined whether the load rate will increase without stopping the operation of the crane 10. The operation of the load increase prevention device 1 in this case is the operation obtained by excluding steps S1 and S2 from the flowchart of the operation determination process shown in FIGS. 9 and 10. [Explanation of symbols]

[0084] 1. Load increase prevention device 2 Angle sensor (attitude detection device) 3 Load sensor (actual load detection device) 4 Storage device 5 Controller (determination means, restriction means, permission means, storage control means, stop means) 6. Displays (chart display devices, graph display devices) 10 Crane 11 Undercarriage 12 Upper rotating body 13 Cab 14. Boom 15 Jib 16 Mast 17 Counterweight 18 Rear strut 19 Front strut 20 Boom guy lines 21,22 Backstop 23 Strut guy link 24 Jib guy line 25 Boom hoisting winch 26 Jib hoisting winch 27 Main winch 28 Auxiliary winch 29 Boom hoisting rope 30,31 Sieve block 32 Jib hoisting rope 33 Guide sheave 34,35 Sheave block 36 Main winding rope 37, 38, 39 Main winding guide sheave 40 Main winding point sheave 41 Main hook 42 Sheaves 43 Auxiliary rope 44, 45, 46 Auxiliary winding guide sheave 47 Auxiliary hoisting point sheave 48 Auxiliary Hook 49 Winch 50 Swivel

Claims

1. an attitude detection device for detecting the attitude of the crane; an actual load detection device for detecting the actual load of the load suspended by the crane; a storage device that stores a predetermined load, which is an allowable value of the actual load, for each posture of the crane; a determination means for determining whether a load factor, which is a ratio of the actual load to the predetermined load, will increase when it is assumed that the attitude of the crane is changed for each of the plurality of parts from the current attitude of the plurality of parts of the crane detected by the attitude detection device to a virtual attitude in which each of the plurality of parts has slightly changed; a limiting means for limiting an operation that increases the load factor among operations of each of the plurality of parts that changes the attitude of the crane from the current attitude to the virtual attitude when the determining means determines that the load factor will increase and the actual load will exceed the predetermined load when it is assumed that the attitude of the crane is changed from the current attitude to the virtual attitude; an allowing means for allowing, when the determining means determines that the load factor will decrease when it is assumed that the attitude of the crane is changed from the current attitude to the virtual attitude, an operation that reduces the load factor among operations of each of the plurality of parts that changes the attitude of the crane from the current attitude to the virtual attitude; A device for preventing load increase on a crane, comprising:

2. a storage control means for storing the determination result by the determination means in the storage device in association with the attitude of the crane; the limiting means, when the determination result corresponding to the current attitude of the crane is that the load factor will increase and the actual load will exceed the predetermined load when it is assumed that the attitude of the crane is changed from the current attitude to the virtual attitude, limits an operation that increases the load factor among operations of each of the plurality of parts that changes the attitude of the crane from the current attitude to the virtual attitude, 2. The device for preventing load increase on a crane according to claim 1, wherein the allowing means allows an operation that reduces the load factor among operations of each of the plurality of parts that changes the attitude of the crane from the current attitude to the virtual attitude, when the determination result corresponding to the current attitude of the crane is a determination result that the load factor will decrease when it is assumed that the attitude of the crane is changed from the current attitude to the virtual attitude.

3. a stopping means for stopping the operation of the crane when the actual load exceeds the predetermined load, 2. The device for preventing load increase of a crane according to claim 1, wherein the determining means makes the determination when the crane is stopped.

4. The load increase prevention device for a crane according to any one of claims 1 to 3, further comprising a graphic display device that displays a graphic showing the determination result by the determination means superimposed on a graphic that simulates the posture of the crane.

5. 5. The load increase prevention device for a crane according to claim 1, further comprising a graph display device that displays a graph of the change in the load factor relative to the change in the attitude of the crane.

6. 6. The device for preventing load increase of a crane according to claim 5, wherein the graph display device displays a line indicating the working radius of the crane by superimposing it on the graph.

7. 7. The load increase prevention device for a crane according to claim 5, wherein the graph display device displays, in a line or by switching, the graphs showing changes in the load factor with respect to changes in the posture of a plurality of parts of the crane that contribute to changes in the posture of the crane.

8. 7. The load increase prevention device for a crane according to claim 5 or 6, wherein the graph display device displays, as a three-dimensional graph, changes in the load factor relative to changes in posture at each of a plurality of parts of the crane that contribute to changes in the posture of the crane.

9. 9. The device for preventing load increase of a crane according to claim 1, wherein the current posture is a posture when the crane is in an overload state.

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