Crane equipped with boom device

Abstract

The present invention provides a crane equipped with a boom device that allows operations to be performed using the main boom even when the lower structure is stored below the main boom. [Solution] A crane comprising a main boom for the crane, an extension jib which is a lower structure positioned below the main boom, a hook attached to a wire rope extended from the tip of the main boom, a boom state detection unit 31 for detecting the state of the main boom, and a boom operation control unit 32 for controlling the operation of the main boom, wherein the boom operation control unit 32 controls the operation of the main boom to avoid contact between the extension jib, the wire rope and the hook, according to the state of the main boom detected by the boom state detection unit 31.

Description

Technical Field

[0001] The present invention relates to a crane having a boom device provided with an extension jib, such as a mini crawler crane.

Background Art

[0002] As a boom device provided with an extension jib, for example, there is a configuration disclosed in Patent Document 1. The boom device disclosed in Patent Document 1 includes an extension jib attached to the tip of the main body side boom. And in the posture for storing the extension jib, the extension jib is arranged on the side surface of the main body side boom.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration disclosed in Patent Document 1, the extension jib is stored on the side of the main body side boom. However, for example, when mounting a boom device on a small machine that needs to suppress the overall width, it is difficult to set a space for storing the extension jib on the side of the machine body. Therefore, a configuration for storing the extension jib below the main body side boom can be considered. However, in the configuration for storing the extension jib below the main body side boom, since the extension jib is stored directly below the sheave provided on the main body side boom, there is a problem that it is impossible to perform a lifting operation using the main body side boom in the state where the extension jib is stored. In view of the above problems, an object of the present invention is to provide a crane provided with a boom device that can perform an operation using the main body side boom even in a state where a lower structure such as an extension jib is stored below the main body side boom.

Means for Solving the Problems

[0005] A crane according to one aspect of the present invention comprises a main boom for the crane, a substructure, a hook, a boom state detection unit, and a boom operation control unit. The substructure is positioned below the main boom. The hook is attached to a wire rope that is extended from the tip of the main boom. The boom operation control unit controls the movement of the main boom. Furthermore, the boom operation control unit controls the movement of the main boom to avoid contact between the substructure, the wire rope, and the hook, according to the state of the main boom detected by the boom state detection unit. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a crane equipped with a boom device that allows work to be performed using the main boom even when the lower structure is stored below the main boom. [Brief explanation of the drawing]

[0007] [Figure 1] This is a side view showing the configuration of a crane equipped with a boom device. [Figure 2] This is a side view showing the configuration of the boom device with the extended jib in the stowed position (third stowed position). [Figure 3] This is a side view showing the configuration of the boom apparatus with the extended jib in the working position. [Figure 4] This is a side view showing the configuration of the boom device with the extended jib in the stowed position (first stowed position). [Figure 5] This is a view along line V in Figure 4. [Figure 6] This is a cross-sectional view taken along the line VI-VI in Figure 5. [Figure 7] This is a view taken along line VII in Figure 5. [Figure 8] This diagram shows the configuration of the jib holding member. [Figure 9] Figure 8 shows a cross-sectional view along the line IX-IX. [Figure 10] This is a view from the X-ray arrow in Figure 9. [Figure 11]This is a view from the direction of line XI in Figure 4. [Figure 12] This diagram shows the operation of the boom mechanism when the extension jib changes position from the working position to the first stowed position. [Figure 13] This diagram illustrates the operation of the boom apparatus when the attitude of the extension jib changes, and is a side view showing the configuration of the boom apparatus when the extension jib is in the retracted position (second retracted position). [Figure 14] This diagram shows a control block that performs interference avoidance control. [Figure 15] This diagram shows the state of the boom device when interference avoidance control is performed. [Figure 16] This diagram shows the state of the boom device when interference avoidance control is performed. [Figure 17] This figure shows the state of the boom device when interference avoidance control is not performed. [Modes for carrying out the invention]

[0008] The boom device and the crane equipped with the boom device according to the present invention will be described below with appropriate reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship and ratio of thickness and planar dimensions may differ from those in reality, and there may be differences in the dimensional relationships and ratios between drawings. Furthermore, the embodiments shown below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the material, shape, structure, arrangement, etc., of the components.

[0009] (Embodiment) <Crane configuration> As shown in Figure 1, the crane 1 comprises a traveling section 2, a machine frame 4, a boom device 6, an outrigger device 8, and a boom luffing cylinder 10. Note that in Figure 1, the configurations of the traveling section 2, machine frame 4, boom device 6, and outrigger device 8 are simplified in some parts. Furthermore, as shown in Figure 1, Crane 1 is a small crawler crane (mini crawler crane). In the following description and drawings, the direction in which the crane 1 moves forward may be described as "front", and the direction in which the crane 1 moves backward may be described as "rear".

[0010] In the following description and drawings, the left side when the crane 1 moves forward may be shown as "left side", and the right side when the crane 1 moves forward may be shown as "right side". Therefore, in the following description and drawings, the perspective of viewing the crane 1 from the left side is regarded as "left side view", and the perspective of viewing the crane 1 from the right side is regarded as "right side view". In addition, in the following description, "left side view" and "right side view" may be collectively described as "side view". After the crane 1 travels by the traveling unit 2 in a traveling posture (not shown) and moves to the work location, the outrigger device 8 is extended as shown in FIG. 1 to ensure the stability of the machine frame 4. Then, after the boom device 6 is erected and extended, the posture of the extension jib EJ provided in the boom device 6 is changed from the storage posture shown in FIGS. 1 and 2 to the working posture shown in FIG. 3, and the load is lifted by the hook F provided in the extension jib EJ to perform the loading and unloading work.

[0011] The boom hoisting cylinder 10 is a cylinder that hoists the main body side boom 61 with respect to the machine frame 4, and is formed by using, for example, a derrick cylinder. In the embodiment, as an example, the case where the boom hoisting cylinder 10 is formed by using a pair of two derrick cylinders arranged on the left and right sides (left side and right side) of the main body side boom 61 in a plan view will be described. In FIG. 1, only one of the pair of two derrick cylinders (boom hoisting cylinder 10) is shown.

[0012] The working posture is a posture in which the extension jib EJ is arranged on the tip side of the main body side boom 61. That is, the working posture is a posture in which the extension jib EJ is moved from below the main body side boom 61. Therefore, the extension jib EJ forms a lower structure arranged below the main body side boom 61 in the storage posture. The stowed position is one in which, in a plan view, the extension jib EJ overlaps the main boom 61, and the extension jib EJ is positioned below the main boom 61. Furthermore, the stowed position can change between the first stowed position, the second stowed position, and the third stowed position.

[0013] The first storage position, as shown in Figure 4, is the position in which the boom-side connecting section 62 and the jib-side connecting section 63 are connected from the working position, and the extension jib EJ is moved below the main body boom 61. The second stowed position is the position in which the boom-side connecting section 62 and the jib-side connecting section 63 are separated from the first stowed position. A detailed explanation of the second stowed position using diagrams will be provided later. The third storage position is the position in which the extension jib EJ is moved toward the base end of the main body boom 61 from the second storage position, as shown in Figures 1 and 2.

[0014] In this embodiment, as an example, we will describe a case where the third storage position is such that, when viewed from above, the position of the jib-side connecting portion 63 does not overlap with the tip of the main body-side boom 61 (see Figures 1 and 2). In other words, when the posture of the extension jib EJ changes from the third stowed posture to the working posture, or when it changes from the working posture to the third stowed posture, the posture of the extension jib EJ changes between the third stowed posture and the working posture to the first stowed posture and the second stowed posture shown in Figure 4. The attitude changes of the extended jib EJ will be discussed later.

[0015] Hook F is attached to the boom device 6 and to the end of the wire rope W that is unfurled from the tip of the extension jib EJ via the main boom 61. In other words, in the working position, the hook F is attached to a single wire rope W that is extended from the tip of the extension jib EJ via the main boom 61 and the extension jib EJ. Furthermore, the hook F is attached to the wire rope W that is extended from the tip of the boom 61 on the main body.

[0016] The boom device 6 includes an extension jib EJ and a hook F, as well as a main body boom 61, a boom-side connecting part 62, a jib-side connecting part 63, a stopper 64, and a jib holding member 20. The main body boom 61 is a boom for crane 1 and can extend and retract in multiple stages (for example, five stages). In addition, the main body boom 61 can be raised and lowered relative to the machine frame 4. The boom-side connecting section 62 is attached to the tip of the main body boom 61 and is connected to the jib-side connecting section 63 by the jib-side connecting pin P1. The jib-side connecting pin P1 is a removable pin.

[0017] The jib-side connecting section 63 is attached to the base end of the extension jib EJ. Furthermore, the jib-side connecting section 63 connects the main body boom 61 and the extension jib EJ together with the boom-side connecting section 62 when the extension jib EJ is in the working position or the first stowed position. Therefore, the jib-side connecting portion 63 is attached to the base end of the substructure (extension jib EJ) and forms a structure-side connecting portion that connects the main body-side boom 61 and the substructure (extension jib EJ) together with the boom-side connecting portion 62.

[0018] The stopper 64 is attached to the lower surface of the main body boom 61 and, as shown in Figures 2 and 4, contacts the outer surface of the extension jib EJ (the upper surface of the extension jib EJ in the retracted position) when the extension jib EJ is in the retracted position. Furthermore, as shown in Figures 5 to 7, the stopper 64 is formed by combining three plate materials 64a to 64c in a U-shape, which together form a space with the lower surface of the main body boom 61.

[0019] Furthermore, the stopper 64 includes a stopper-side pin insertion hole 70, a retractable pin sensor 71, and a pin stopper 72. The stopper-side pin insertion hole 70 is a hole that penetrates two of the three U-shaped plate materials 64a to 64c, specifically the two plate materials 64a and 64b, which are arranged in the left-right direction (left-right direction in Figures 5 and 6), and is formed so that the storage pin P2, which will be described later, can be inserted and removed.

[0020] Figures 5 to 7 show the state in which the storage pin P2 is stored in a stopper-side pin storage hole, which is formed at a different position from the stopper-side pin insertion hole 70. The storage pin P2 is stored in the stopper-side pin storage hole when the extension jib EJ is in the working position, the first storage position, and the second storage position. The storage pin sensor 71 is formed, for example, using a proximity sensor, and detects the state in which the storage pin P2 is inserted into the stopper-side pin insertion hole 70. Furthermore, when the retractable pin sensor 71 detects that the retractable pin P2 is inserted into the stopper-side pin insertion hole 70, it outputs an information signal including the detected state to the jib attitude detection unit, which will be described later.

[0021] The pin stopper 72 is formed by combining a pair of plate materials and a rod-shaped member connecting the pair of plate materials, and is pushed to a position where it overlaps laterally with the stopper-side pin insertion hole 70 by the elastic force generated by the spring member 73. Furthermore, the pin stopper 72 is positioned to overlap laterally with the stopper-side pin insertion hole 70 when the extension jib EJ is in the working position, the first stowed position, and the second stowed position. On the other hand, when the extension jib EJ is in the third stowed position, the pin stopper 72 is pushed against the elastic force of the spring member 73 by the cylinder bracket 83 (described later), which is part of the extension jib EJ, and moves to a position where it does not overlap laterally with the stopper-side pin insertion hole 70. Furthermore, when the pin stopper 72 moves to a position where it does not overlap laterally with the stopper-side pin insertion hole 70, the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a, which will be described later, will overlap laterally.

[0022] (Jib holding member) The jib holding member 20 is a member that holds the extension jib EJ below the main body boom 61 in the second and third stowed positions. Therefore, the jib holding member 20 forms a structural holding member that holds the lower structure (extension jib EJ) in the second and third stowed positions. Furthermore, as shown in Figures 8 to 11, the jib holding member 20 includes a guide roller 21, a suspension bracket 22, a sliding mechanism 23, a movable pin P3, and a knob bolt 24.

[0023] The guide roller 21 is positioned on the lower surface of the main body boom 61 that faces the extension jib EJ when the boom is stowed. The axis of rotation of the guide roller 21 is oriented laterally. Furthermore, the guide roller 21 is in contact with the wire rope W in a rotatable state when in the stowed position. Note that the illustration of the state in which the guide roller 21 and the wire rope W are in contact is omitted.

[0024] The suspension brackets 22 are made up of pairs and are positioned on the sides (both sides) of the main body boom 61. Furthermore, the suspension bracket 22 is equipped with a suspension lever 22a and a movable pin P3. The suspension lever 22a is a lever whose axis of rotation is oriented laterally and is positioned outside the suspension bracket 22. The movable pin P3 is a pin that can protrude inward from the suspension bracket 22 as the suspension lever 22a rotates. In Figure 9, the movable pin P3 in the state where it is protruding inward from the suspension bracket 22 is shown by a solid line, and the movable pin P3 in the state where it is retracted inside the suspension bracket 22 is shown by a dashed line.

[0025] The movable pin P3 is pushed inward into the suspension bracket 22 by the coil spring 22b built into the suspension bracket 22. In addition, as the rotating suspension lever 22a moves outward into the suspension bracket 22 while contacting the inclined portion 22c, the movable pin P3 moves inward into the suspension bracket 22. Furthermore, the shape of the movable pin P3 is such that it can be inserted into the jib-side opening 82a, which will be described later.

[0026] Therefore, when the jib-side opening 82a and the suspension bracket 22 are superimposed, and the movable pin P3 is inserted into the jib-side opening 82a with the pin protruding inward from the suspension bracket 22, the extension jib EJ is connected to the suspension bracket 22 in the stowed position (see Figures 2 and 4).

[0027] The sliding mechanism 23 holds the suspension bracket 22 so that it can move along the length of the main body boom 61. Furthermore, the sliding mechanism 23 allows the suspension bracket 22 to which the extension jib EJ is connected to move so that the posture of the extension jib EJ changes between the second and third stowed positions. In Figure 8, the range in which the suspension bracket 22 can move is indicated as the "slide amount".

[0028] Furthermore, the range in which the suspension bracket 22 can be moved can be adjusted by changing the amount of tightening of the two adjustment bolts 22d. In Figure 8, the amount of adjustment in the range in which the suspension bracket 22 can be moved is indicated as the "adjustment range". Specifically, the slide mechanism 23 comprises a housing portion 23a, a bearing portion 23b, and a cover 23c.

[0029] The housing portion 23a is formed using two plate materials arranged parallel to the length direction of the main body boom 61 and is fixed to the side of the main body boom 61. The bearing portion 23b is formed, for example, using a roller follower, and its outer surface is in contact with the two plate materials forming the housing portion 23a.

[0030] Furthermore, the bearing section 23b is attached to the upper part of the suspension bracket 22. The cover 23c, along with the side of the main body boom 61 and the two plates forming the housing portion 23a, is a plate that forms the portion to which the bearing portion 23b of the suspension bracket 22 is attached, and the space that houses the bearing portion 23b.

[0031] The retraction pin P2 is a pin that connects the stopper 64 and the pin-supported part (cylinder bracket 83), which will be described later, when the extension jib EJ is in the third retraction position. Note that the retraction pin P2 is not shown in Figures 1 and 2. Specifically, when the extension jib EJ is in the third stowed position, it is inserted into the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a, which will be described later.

[0032] Therefore, the retraction pin P2 is stored in the stopper-side pin storage hole when the extension jib EJ is in the working position, the first retraction position, and the second retraction position. On the other hand, when the extension jib EJ is in the third retraction position, it is a pin that connects the stopper 64 and the cylinder bracket 83 while passing through them. The knob bolt 24 is installed by passing through the cover 23c, and the tightening action presses the tip of the knob bolt against the suspension bracket 22, thereby fixing the position of the suspension bracket 22.

[0033] As described above, the jib holding member 20 can move the extension jib EJ toward the base end of the main body boom 61 while the boom-side connecting portion 62 and the jib-side connecting portion 63 are separated. This allows the jib holding member 20 to change the posture of the extension jib EJ between the second stowed posture and the third stowed posture. In Figure 8, the suspension bracket 22 moved to the second stowed posture position is shown by a solid line, and the suspension bracket 22 moved to the third stowed posture position is shown by a dashed line.

[0034] <Specific configuration of the extension jib> The extended jib EJ comprises a jib-side boom 80, a jib luffing cylinder 81, and a jib-side suspension section 82. (Jib boom) The jib boom 80 can extend and retract in multiple stages (for example, four stages), and can also be raised and lowered relative to the main body boom 61.

[0035] (Jib luffing cylinder) The jib luffing cylinder 81 is a cylinder that extends and retracts when operating the jib boom 80 in the working position and when changing the position of the extension jib EJ between the stowed position and the working position. The jib luffing cylinder 81 is formed using a pair of derrick cylinders, for example, which are arranged on both the left and right sides (left and right) of the extension jib EJ in a plan view. Note that in the figure, only one of the pair of derrick cylinders (jib luffing cylinder 81) is shown.

[0036] One end (the tube-side end) of the jib luffing cylinder 81 is connected to the underside of the extension jib EJ in the working position via a cylinder bracket 83. The cylinder bracket 83 has a cylinder-side pin insertion hole 83a from which the storage pin P2 can be inserted and removed.

[0037] As shown in Figure 4, the portion of the cylinder bracket 83 in which the cylinder-side pin insertion hole 83a is formed does not overlap laterally with the stopper 64 when the extension jib EJ is in the first stowed position. Similarly, the portion of the cylinder bracket 83 in which the cylinder-side pin insertion hole 83a is formed does not overlap laterally with the stopper 64 when the extension jib EJ is in the second stowed position. Furthermore, as shown in Figure 2, the portion of the cylinder bracket 83 in which the cylinder-side pin insertion hole 83a is formed overlaps laterally with the stopper 64 when the extension jib EJ is in the third stowed position.

[0038] In other words, the cylinder bracket 83, which is part of the extension jib EJ, forms a pinned support portion that does not overlap the stopper 64 laterally when the extension jib EJ is in the second stowed position, but overlaps the stopper 64 laterally when the extension jib EJ is in the third stowed position. The other end (the end on the piston rod side) of the jib luffing cylinder 81 is connected to a linkage mechanism 84. The link mechanism 84 comprises a first arm portion 84a and a second arm portion 84b.

[0039] One end of the first arm 84a is connected to the other end of the jib luffing cylinder 81 via a rotating shaft (not shown) parallel to the width direction of the crane 1. The other end of the first arm portion 84a is connected to the boom-side connecting portion 62 via the first arm-side connecting pin P4. The connecting pin P4 on the first arm side is a pin that can be easily inserted and removed.

[0040] One end of the second arm section 84b is coaxially connected to the other end of the jib luffing cylinder 81 via a rotation axis parallel to the width direction of the crane 1, and to one end of the first arm section 84a. The other end of the second arm portion 84b is connected to the jib-side connecting portion 63 via the second arm-side connecting pin P5. The second arm connecting pin P5 is a pin that is always inserted, except during maintenance.

[0041] (Jib side suspension section) The jib-side suspension section 82 is formed using a pair of plate materials arranged in a thickness direction parallel to the direction in which the pair of jib luffing cylinders 81 are arranged. Furthermore, the jib-side suspension section 82 is positioned between a pair of jib luffing cylinders 81 and connected to the side of the jib-side boom 80, and as shown in Figure 3, it protrudes downward from the jib-side boom 80 in the working position. The portion of the jib-side suspension section 82 that protrudes beyond the jib-side boom 80 has a jib-side opening 82a formed therein, into which a movable pin, described later, can be inserted and removed.

[0042] <Changes in the attitude of the extended jib> The attitude changes of the extended jib EJ will be explained below, referring to Figures 1 through 11, and using Figures 12 and 13. The following describes the operation of changing the posture of the extension jib EJ from the working posture to the third stowed posture, via the first and second stowed postures. When changing the posture of the extension jib EJ from the working posture shown in Figure 3 to the first stowed posture shown in Figure 4, the jib-side connecting part 63 rotates relative to the boom-side connecting part 62, with the central axis of the jib-side connecting pin P1 as the center of rotation, causing the extension jib EJ to rotate downward relative to the main body boom 61, as shown in Figure 12.

[0043] Then, as shown in Figure 4, when the extension jib EJ is in the first stowed position, the outer surface of the extension jib EJ (the outer surface of the jib-side boom 80) contacts the stopper 64 from below. When the extension jib EJ is in its first stowed position, the position of the jib-side connecting portion 63 coincides with the tip of the main body boom 61 when viewed from above or below, making it impossible to attach the hook F to the wire rope W. Therefore, even when the extension jib EJ is stowed, it is impossible to perform work using the main body boom 61.

[0044] When changing the posture of the extension jib EJ from the first stowed posture shown in Figure 4 to the second stowed posture, first, the jib-side suspension part 82 and the suspension bracket 22 are aligned when viewed from the side. Furthermore, the jib-side opening 82a is moved to the position of the movable pin P3, and the suspension lever 22a is rotated to make the movable pin P3 protrude inward from the suspension bracket 22 and is inserted into the jib-side opening 82a. Subsequently, as shown in Figure 13, the jib-side connecting pin P1 and the first arm-side connecting pin P4 are removed, separating the boom-side connecting section 62 and the jib-side connecting section 63, thereby changing the posture of the extended jib EJ to the second stowed posture.

[0045] As shown in Figure 13, in the second stowed position, the extension jib EJ is attached to the main boom 61 suspended only by the suspension bracket 22. In other words, the extension jib EJ is supported by the main boom 61 at only one point. Therefore, the sliding mechanism 23 makes it possible to move the suspension bracket 22 along the length of the main boom 61. Next, the operator moves the extension jib EJ towards the base end of the main boom 61, changing the posture of the extension jib EJ to the third stowed posture, as shown in Figure 2.

[0046] At this time, as the extension jib EJ moves toward the base end of the main body boom 61, the cylinder bracket 83 pushes up the pin stopper 72, and the position of the pin stopper 72 moves to a position where it does not overlap laterally with the stopper-side pin insertion hole 70. Then, the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a overlap laterally, and the storage pin P2 is inserted into the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a. When the retractable pin P2 is inserted into the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a, the extension jib EJ is fixed and supported to the main body boom 61 at two points, including the fact that the movable pin P3 is inserted into the jib-side opening 82a.

[0047] Furthermore, when the storage pin P2 is inserted into the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a, as shown in Figure 2, the position of the jib-side connecting portion 63 does not overlap with the tip of the main body boom 61 when viewed from above. Therefore, even when the extension jib EJ is stored, it is possible to perform work using the main body boom 61.

[0048] <Interference avoidance control> The following explanation will describe the control (interference avoidance control) that avoids interference between the extension jib EJ, the wire rope W, and the hook F, referring to Figures 1 to 13 and using Figures 14 to 17. Interference avoidance control is a type of control performed by, for example, the control block shown in Figure 14. The control block that performs interference avoidance control includes a jib attitude detection unit 30, a boom state detection unit 31, and a boom operation control unit 32. The control block includes, for example, a controller (not shown) provided in the machine frame 4.

[0049] The jib attitude detection unit 30 detects the attitude of the extension jib EJ in response to the information signal input from the retractable pin sensor 71, and outputs the information signal including the detected attitude to the boom operation control unit 32. Therefore, the jib attitude detection unit 30 forms a structure attitude detection unit that detects the attitude of the substructure (extension jib EJ).

[0050] As described above, in this embodiment, the state in which the storage pin P2 is inserted into the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a is the state in which the posture of the extension jib EJ has changed to the third storage posture. Therefore, the storage pin sensor 71, which detects that the storage pin P2 is inserted into the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a, outputs an information signal to the jib posture detection unit 30 indicating that the posture of the extension jib EJ is the third storage posture. Therefore, when the jib attitude detection unit 30 determines that the retraction pin P2 has passed through the stopper 64 and the pin-supported part (cylinder bracket 83), it detects that the attitude of the extension jib EJ is the third retraction attitude.

[0051] The boom state detection unit 31 detects the state of the main unit boom 61 and outputs an information signal including the detected state to the boom operation control unit 32. Furthermore, the boom state detection unit 31 includes a boom length detection unit 31a for detecting the length of the main body boom 61 and a boom luffing angle detection unit 31b for detecting the luffing angle of the main body boom 61. Therefore, the boom state detection unit 31 detects the length of the main body boom 61 and the luffing angle of the main body boom 61 as the state of the main body boom 61.

[0052] The boom operation control unit 32 controls the operation of the main body boom 61 in accordance with information signals input from the jib attitude detection unit 30 and the boom state detection unit 31, so as to avoid contact between the extension jib EJ (substructure) and the wire rope W and hook F. When controlling the operation of the main body boom 61, it outputs the calculated control signal to the actuator AC (boom luffing cylinder 10, boom extension cylinder 12). The boom extension cylinder 12 is a cylinder that extends and retracts the main body boom 61, which is a multi-stage boom. Furthermore, the boom operation control unit 32 includes a boom luffing angle control unit 32a that controls the luffing angle of the main body boom 61, and a boom length control unit 32b that controls the length of the main body boom 61.

[0053] When the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is in the third stowed position, the boom luffing angle control unit 32a controls the luffing angle of the main body boom 61 to avoid contact between the extension jib EJ and the wire rope W and hook F, according to the length of the main body boom 61 detected by the boom length detection unit 31a. When the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is in the third stowed position, the boom length control unit 32b controls the length of the main body boom 61 to avoid contact between the extension jib EJ and the wire rope W and hook F, according to the luffing angle of the main body boom 61 detected by the boom luffing angle detection unit 31b.

[0054] As described above, when the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is in the third stowed position, the boom operation control unit 32 controls the operation of the main body boom 61 to avoid contact between the extension jib EJ and the wire rope W and hook F, according to the state of the main body boom 61 detected by the boom state detection unit 31.

[0055] The following describes the specific processes performed by the boom motion control unit 32. The boom motion control unit 32 performs calculations such that the following conditions (1) to (3) are satisfied. X_J=L_J*cosθ+S_J*sinθ+R_J … (1) X_B=L_B*cosθ+S_B*sinθ-(R_B+φd) … (2) X_H=L_B*cosθ+S_B*sinθ-H … (3)

[0056] "L_J" is the length from the center of the point where the extension jib EJ protrudes toward the tip of the main body boom 61 in the third stowed position, to the boom foot 6a of the main body boom 61, as shown in Figure 15, and is a constant determined by the configuration of the boom device 6. "S_J" is the downward offset amount from the center of the point where the extension jib EJ protrudes toward the tip of the main body boom 61 in the third stowed position, to the boom foot 6a, as shown in Figure 15, and is a constant determined by the configuration of the boom device 6. Note that "S_J" is considered positive if it is below the boom foot 6a.

[0057] "R_J" is the radius of the point where the extension jib EJ protrudes toward the tip of the main boom 61 in the third stowed position, and is a constant determined by the configuration of the boom device 6. If the point where the extension jib EJ protrudes toward the tip of the main boom 61 is an angle rather than an arc, "R_J" is set to 0. "L_B" is the length from the center of the sheave 6b located at the tip of the main body boom 61 to the boom foot 6a, as shown in Figure 15, and is a variable detected by the boom length detection unit 31a.

[0058] "S_B" is the downward offset amount from the center of the sheave 6b to the boom foot 6a, as shown in Figure 15, and is a constant determined by the configuration of the boom device 6. Note that "S_B" is considered positive when it is below the boom foot 6a. "R_B" is the radius of the sheave 6b, and is a constant determined by the configuration of the boom device 6.

[0059] "φd" is the diameter of the wire rope W and is a constant determined by the configuration of the boom device 6. "H" is the distance from the center of the sheave 6b to the outermost part of the attachment (hook F), as shown in Figure 15, and is a constant determined by the configuration of the boom device 6. "θ" is the elevation angle of the main body boom 61, and is a variable detected by the boom elevation angle detection unit 31b.

[0060] The boom operation control unit 32 then performs calculations to ensure that X_B > X_J at all times. As a result, as shown in Figures 15 and 16, the main body boom 61 can be retracted to a length that does not interfere with the wire rope W. Furthermore, the boom motion control unit 32 performs calculations so that X_H > X_J at all times. As a result, as shown in Figures 15 and 16, the main body boom 61 can be retracted to a length that does not interfere with the attachment (hook F). Furthermore, if interference avoidance control is not performed, as shown in Figure 17, even in the third stowed position, depending on the length and elevation angle of the main body boom 61, the extension jib EJ and the wire rope W or hook F may interfere with each other.

[0061] <Operation / effect> Next, the operation and function of the crane 1 equipped with the boom device 6 will be described with reference to Figures 1 to 17. When using crane 1, the position of the extension jib EJ is changed from the stowed position to the working position, as shown in Figure 3. Furthermore, the main body boom 61 is raised to an angle appropriate for the cargo handling operation and extended to a length appropriate for the operation. Then, cargo handling operations such as lifting the load with the hook F are performed. In this case, when performing work using a hook F attached to a wire rope W that is extended from the tip of the main boom 61, without requiring the extension jib EJ, it is impossible to perform the work in the first and second stowed positions.

[0062] In this embodiment, the posture of the extension jib EJ can be changed between a second stowed posture and a third stowed posture, which is a posture in which the extension jib EJ is moved toward the base end of the main boom 61. By moving the extension jib EJ toward the base end of the main boom 61, it is possible to secure space below the tip of the main boom 61. This makes it possible to perform work using a hook F attached to a wire rope W that is extended from the tip of the main boom 61, with the extension jib EJ positioned below the main boom 61.

[0063] <Effects and Effects of the Embodiment> The boom device 6 of this embodiment can provide the following functions and effects. (1) The rig is equipped with a jib holding member 20 that holds the extension jib EJ below the main body boom 61 in the second and third storage positions. The second storage position is a position in which the boom-side connecting portion 62 and the jib-side connecting portion 63 are separated from the first storage position, and the third storage position is a position in which the extension jib EJ is moved towards the base end of the main body boom 61 from the second storage position. As a result, it becomes possible to provide a boom device 6 that allows work to be performed using the main body boom 61 even when the extension jib EJ is retracted.

[0064] (2) The third storage position is a position in which, when viewed from above, the position of the jib-side connecting portion 63 does not overlap with the tip of the main body-side boom 61. As a result, even when the extension jib EJ is retracted, it is possible to perform work using the main body boom 61 while preventing interference between the jib-side connecting section 63 and the wire rope W.

[0065] (3) The jib holding member 20 is equipped with a guide roller 21 whose axis of rotation is oriented laterally. The guide roller 21 is in contact with the wire rope W in a rotatable state when in the stowed position. As a result, damage to the wire rope W can be suppressed even when the extension jib EJ is retracted.

[0066] (4) The jib holding member 20 is equipped with a suspension bracket 22 positioned on the side of the main body boom 61. The extension jib EJ is connected to the suspension bracket 22 in the second and third stowed positions. As a result, it is possible to hold the extension jib EJ even when the boom-side connecting portion 62 and the jib-side connecting portion 63 are separated.

[0067] (5) The jib holding member 20 includes a sliding mechanism 23 that holds the suspension bracket 22 so that it can move along the length of the main body boom 61. The sliding mechanism 23 also allows the suspension bracket 22 to which the extension jib EJ is connected to to move so that the posture of the extension jib EJ changes between the second stowed posture and the third stowed posture. As a result, it becomes possible to change the posture of the extension jib EJ from the second stowed position to the third stowed position by manual labor by workers, without the need for actuators or other devices.

[0068] A crane 1 equipped with the boom device 6 of this embodiment can achieve the following functions and effects. (6) The boom device 6 is provided which can change the attitude of the extended jib EJ between a second stowed position and a third stowed position. As a result, it is possible to provide a crane 1 equipped with a boom device 6 that can perform work using the main body boom 61 even when the extension jib EJ is retracted. Furthermore, even with a crane 1 that has a narrow overall width, it is possible to store the extension jib EJ. Furthermore, it becomes possible to reduce the area of ​​interference when the main body boom 61 rotates, and to improve the degree of freedom in positioning the outrigger device 8, making it easier to maneuver in confined spaces, for example. Furthermore, the extension jib EJ acts as a counterweight, improving the stability of crane 1.

[0069] (7) The machine base frame 4 to which the main body boom 61 is mounted so as to be able to be raised and lowered, and the boom luffing cylinder 10 for raising and lowering the main body boom 61 relative to the machine base frame 4. The boom luffing cylinder 10 is formed using a pair of derrick cylinders arranged on both the left and right sides of the main body boom 61 in a plan view. As a result, it becomes easier to secure space to store the extension jib EJ.

[0070] (8) The system includes a jib attitude detection unit 30 for detecting the attitude of the extension jib EJ, a boom state detection unit 31 for detecting the state of the main body boom 61, and a boom operation control unit 32 for controlling the operation of the main body boom 61. When the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is the third stowed position, the boom operation control unit 32 controls the operation of the main body boom 61 to avoid contact between the extension jib EJ and the wire rope W and hook F, according to the state of the main body boom 61 detected by the boom state detection unit 31. As a result, even when the position of the main boom 61 changes while the extension jib EJ is in the third stowed position, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F.

[0071] (9) The boom state detection unit 31 includes a boom length detection unit 31a that detects the length of the main body boom 61, and the boom operation control unit 32 includes a boom luffing angle control unit 32a that controls the luffing angle of the main body boom 61. When the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is the third stowed attitude, the boom luffing angle control unit 32a controls the luffing angle of the main body boom 61 in accordance with the length of the main body boom 61 detected by the boom length detection unit 31a, so as to avoid contact between the extension jib EJ and the wire rope W and the hook F. As a result, even if the length of the main boom 61 changes when the extension jib EJ is in the third stowed position, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F.

[0072] (10) The boom state detection unit 31 includes a boom luffing angle detection unit 31b that detects the luffing angle of the main body boom 61, and the boom operation control unit 32 includes a boom length control unit 32b that controls the length of the main body boom 61. When the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is the third stowed attitude, the boom length control unit 32b controls the length of the main body boom 61 in accordance with the luffing angle of the main body boom 61 detected by the boom luffing angle detection unit 31b, so as to avoid contact between the extension jib EJ and the wire rope W and the hook F. As a result, even when the elevation angle of the main boom 61 changes while the extension jib EJ is in the third stowed position, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F.

[0073] (11) The main body boom 61 is provided with a stopper 64 that contacts the outer surface of the extension jib EJ when the extension jib EJ is in the retracted position. In addition, a part of the extension jib EJ forms a pin-supported portion that does not overlap laterally with the stopper 64 when the extension jib EJ is in the second retracted position, but overlaps laterally with the stopper 64 when the extension jib EJ is in the third retracted position. The jib holding member 20 is provided with a retraction pin P2 that connects the stopper 64 and the pin-supported portion while passing through them when the extension jib EJ is in the third retracted position. Furthermore, when the jib position detection unit 30 determines that the retraction pin P2 has passed through the stopper 64 and the pin-supported portion, it detects that the extension jib EJ is in the third retracted position. As a result, by detecting the essential actions and states performed by operators when changing the posture of the extension jib EJ to the third stowed posture, it becomes possible to detect that the posture of the extension jib EJ is the third stowed posture.

[0074] (12) As a lower structure positioned below the main body boom 61 in the stowed position, an extension jib EJ is provided that is positioned at the tip of the main body boom 61 in the working position. As a result, even when the position of the main boom 61 changes while the extension jib EJ, which is the lower structure, is in the third stowed position, it is possible to perform work using the main boom 61 while avoiding contact between the lower structure and the wire rope W and hook F.

[0075] <Variation> (1) In this embodiment, the boom operation control unit 32 is configured to control the operation of the main body boom 61 so as to avoid contact between the extension jib EJ and the wire rope W and hook F, but it is not limited to this configuration. In other words, the boom operation control unit 32 may be configured to perform, in addition to control to avoid contact between the extension jib EJ and the wire rope W and hook F, control the extension of the main body boom 61 and the jib boom 80, control the pressure and speed associated with the hoisting of the wire rope W, control the pressure and speed generated by the jib luffing cylinder 81 when moving the jib boom 80 in the raising direction, control the speed until the raising of the main body boom 61 is completed, and perform pressure relief.

[0076] Furthermore, the conditions under which control is performed for the extension of the main boom 61, the extension of the jib boom 80, the hoisting of the wire rope W, the regulation of pressure and speed when raising the main boom 61, the regulation of speed until the operation of raising the main boom 61 is completed, and pressure release are not limited to the state in which the extended jib EJ is in the third stowed position. Furthermore, the control that regulates the pressure and speed generated by the jib luffing cylinder 81 when moving the jib boom 80 in the direction of raising it is, for example, a control performed to align the stopper-side pin insertion hole 70 and the cylinder-side pin insertion hole 83a when changing the posture of the extension jib EJ from the second stowed posture to the third stowed posture, and is performed so as not to exceed the normal pressure and speed. (2) In this embodiment, the third stowed position is such that, when viewed from above, the position of the jib-side connecting portion 63 does not overlap with the tip of the main body boom 61, but the invention is not limited to this. That is, for example, depending on the luffing angle of the main body boom 61, the third stowed position may be such that, when viewed from above, the position of the jib-side connecting portion 63 overlaps with the tip of the main body boom 61.

[0077] (3) In this embodiment, the substructure is an extended jib EJ, but it is not limited to this. That is, the substructure may be, for example, a jig for lifting the machine, or a member (slipper) placed between the outrigger device 8 and the ground. Alternatively, the main body boom 61 itself may have a structure with a protruding part at the bottom. The control to avoid contact between the substructure and the wire rope W and hook F is performed, for example, under the condition that the shape of the substructure is known. Also, if the main body boom 61 itself has a structure with a protruding part at the bottom, interference avoidance control is always performed.

[0078] (4) In this embodiment, the jib attitude detection unit 30 determines that the storage pin P2 has passed through the stopper 64 and the pinned support portion, and detects that the attitude of the extension jib EJ is the third storage attitude. However, the embodiment is not limited to this. That is, for example, the configuration may be such that the attitude of the extension jib EJ is the third storage attitude by detecting whether the main body boom 61 is being used, whether the extension jib EJ is being used, or whether the main body boom 61 is being used but the extension jib EJ is not stored on the underside of the main body boom 61.

[0079] (5) In this embodiment, the boom operation control unit 32 is configured to control the operation of the main body boom 61 in accordance with information signals input from the jib attitude detection unit 30 and the boom state detection unit 31, but it is not limited to this. That is, the boom operation control unit 32 may be configured to control the operation of the main body boom 61 in accordance with the state of the main body boom 61 detected by the boom state detection unit 31, without using information signals input from the jib attitude detection unit 30, in order to avoid contact between the extension jib EJ (substructure) and the wire rope W and hook F. With this configuration, regardless of the orientation of the extension jib EJ, even if the state of the main boom 61 changes, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F.

[0080] (6) In this embodiment, the boom operation control unit 32 is configured to control the operation of the main body boom 61 when the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is in the third stowed position, but it is not limited to this. That is, the boom operation control unit 32 may be configured to control the operation of the main body boom 61 when the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is in the stowed position, so as to avoid contact between the extension jib EJ and the wire rope W and hook F. With this configuration, it is not limited to when the extension jib EJ is in the third stowed position, but even when the extension jib EJ is in the stowed position, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F, even if the state of the main boom 61 changes.

[0081] (7) In this embodiment, the boom luffing angle control unit 32a is configured to control the luffing angle of the main body boom 61 when the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is the third stowed position, but it is not limited to this. That is, the boom luffing angle control unit 32a may be configured to control the luffing angle of the main body boom 61 in accordance with the length of the main body boom 61 detected by the boom length detection unit 31a, without using the information signal input from the jib attitude detection unit 30, in order to avoid contact between the extension jib EJ and the wire rope W and hook F. With this configuration, regardless of the orientation of the extension jib EJ, even if the length of the main boom 61 changes, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F.

[0082] (8) In this embodiment, the boom length control unit 32b is configured to control the length of the main body boom 61 when the jib attitude detection unit 30 detects that the attitude of the extension jib EJ is in the third stowed position, but it is not limited to this. That is, the boom length control unit 32b may be configured to control the length of the main body boom 61 in accordance with the elevation angle of the main body boom 61 detected by the boom elevation angle detection unit 31b, without using the information signal input from the jib attitude detection unit 30, in order to avoid contact between the extension jib EJ and the wire rope W and hook F. With this configuration, regardless of the posture of the extension jib EJ, even if the elevation angle of the main boom 61 changes, it is possible to perform work using the main boom 61 while avoiding contact between the extension jib EJ and the wire rope W and hook F. [Explanation of Symbols]

[0083] 1...Crane, 2...Travel section, 4...Machine frame, 6...Boom device, 6a...Boom foot, 6b...Sheave, 8...Outrigger device, 10...Boom luffing cylinder, 12...Boom extension cylinder, 20...Jib holding member, 21...Guide roller, 22...Suspension bracket, 22a...Suspension lever, 22b...Coil spring, 22c...Inclined section, 22d...Adjustment bolt, 23...Slide mechanism, 23a...Housing section, 23b...Bearing section, 23c...Cover, 24...Knob bolt, 30...Jib attitude detection section, 31...Boom state detection section, 31a...Boom length detection section, 31b...Boom luffing angle detection section, 32...Boom operation control section, 32a...Boom luffing angle control section, 32b...Boom length control unit, 61...Main body boom, 62...Boom side connecting part, 63...Jib side connecting part, 64...Stopper, 70...Stopper side pin insertion hole, 71...Retractable pin sensor, 72...Pin stopper, 73...Spring member, 80...Jib side boom, 81...Jib luffing cylinder, 82...Jib side suspension part, 82a...Jib side opening, 83...Cylinder bracket, 83a...Cylinder side pin insertion hole, 84...Link mechanism, 84a...First arm section, 84b...Second arm section, EJ...Extension jib, F...Hook, W...Wire rope, AC...Actuator, P1...Jib side connecting pin, P2...Retractable pin, P3...Movable pin, P4...First arm side connecting pin, P5...Second arm side connecting pin

Claims

1. The main boom for the crane, A lower structure positioned below the main body boom, A hook attached to a wire rope that extends from the tip of the boom on the main body, A boom state detection unit for detecting the state of the main body boom, The system includes a boom motion control unit that controls the operation of the main body boom, The boom operation control unit controls the operation of the main body boom in accordance with the state of the main body boom detected by the boom state detection unit, in order to avoid contact between the lower structure, the wire rope, and the hook.

2. A boom device comprising: a main-side boom for a crane; a lower structure capable of changing its position between a working position, which is a position moved from below the main-side boom, and a stowed position, which is a position positioned below the main-side boom; a hook attached to a wire rope extended from the tip of the main-side boom; and a structural holding member that holds the lower structure below the main-side boom in the stowed position. A structural attitude detection unit for detecting the attitude of the aforementioned substructure, A boom state detection unit for detecting the state of the main body boom, The system includes a boom motion control unit that controls the operation of the main body boom, The boom operation control unit controls the operation of the main body boom to avoid contact between the lower structure and the wire rope and the hook, according to the state of the main body boom detected by the boom state detection unit, when the structure attitude detection unit detects that the attitude of the lower structure is the stowed position.

3. The system further comprises a boom-side connecting portion attached to the main body boom, and a structure-side connecting portion attached to the substructure and connecting the main body boom and the substructure together with the boom-side connecting portion, The aforementioned storage posture changes to a first storage posture, which is a posture in which the lower structure is moved below the main body boom while the boom-side connecting portion and the structure-side connecting portion are connected from the working posture; a second storage posture, which is a posture in which the boom-side connecting portion and the structure-side connecting portion are separated from the first storage posture; and a third storage posture, which is a posture in which the lower structure is moved towards the base end of the main body boom from the second storage posture, so that when viewed from above, the position of the structure-side connecting portion does not overlap with the tip of the main body boom. The structural holding member holds the lower structure in the second and third storage positions, The crane according to claim 2, wherein the boom operation control unit controls the operation of the main body boom to avoid contact between the lower structure, the wire rope, and the hook, according to the state of the main body boom detected by the boom state detection unit, when the structure attitude detection unit detects that the attitude of the lower structure is the third stowed position.

4. The system further comprises a boom-side connecting portion attached to the main body boom, and a structure-side connecting portion attached to the substructure and connecting the main body boom and the substructure together with the boom-side connecting portion, The boom state detection unit includes a boom length detection unit that detects the length of the main body side boom, The boom operation control unit includes a boom luffing angle control unit that controls the luffing angle of the main body boom, The crane according to claim 1, wherein the boom luffing angle control unit controls the luffing angle of the main body boom in accordance with the length of the main body boom detected by the boom length detection unit, so as to avoid contact between the lower structure and the wire rope and the hook.

5. The system further includes a structure attitude detection unit for detecting the attitude of the substructure, The aforementioned lower structure is capable of changing its posture between a working posture, which is a posture in which it is moved from below the main body boom, and a stowed posture, which is a posture in which it is positioned below the main body boom. The aforementioned storage posture changes to a first storage posture, which is a posture in which the lower structure is moved below the main body boom while the boom-side connecting portion and the structure-side connecting portion are connected from the working posture; a second storage posture, which is a posture in which the boom-side connecting portion and the structure-side connecting portion are separated from the first storage posture; and a third storage posture, which is a posture in which the lower structure is moved towards the base end of the main body boom from the second storage posture, so that when viewed from above, the position of the structure-side connecting portion does not overlap with the tip of the main body boom. The crane according to claim 4, wherein the boom luffing angle control unit controls the luffing angle of the main body boom to avoid contact between the lower structure and the wire rope and the hook, according to the length of the main body boom detected by the boom length detection unit, when the structure attitude detection unit detects that the attitude of the lower structure is the third stowed position.

6. The system further comprises a boom-side connecting portion attached to the main body boom, and a structure-side connecting portion attached to the substructure and connecting the main body boom and the substructure together with the boom-side connecting portion, The boom state detection unit includes a boom luffing angle detection unit that detects the luffing angle of the main body boom, The boom operation control unit includes a boom length control unit that controls the length of the main body boom, The crane according to claim 1, wherein the boom length control unit controls the length of the main body boom in accordance with the luffing angle of the main body boom detected by the boom luffing angle detection unit, so as to avoid contact between the lower structure, the wire rope and the hook.

7. The system further includes a structure attitude detection unit for detecting the attitude of the substructure, The aforementioned lower structure is capable of changing its posture between a working posture, which is a posture in which it is moved from below the main body boom, and a stowed posture, which is a posture in which it is positioned below the main body boom. The aforementioned storage posture changes to a first storage posture, which is a posture in which the lower structure is moved below the main body boom while the boom-side connecting portion and the structure-side connecting portion are connected from the working posture; a second storage posture, which is a posture in which the boom-side connecting portion and the structure-side connecting portion are separated from the first storage posture; and a third storage posture, which is a posture in which the lower structure is moved towards the base end of the main body boom from the second storage posture, so that when viewed from above, the position of the structure-side connecting portion does not overlap with the tip of the main body boom. The crane according to claim 6, wherein the boom length control unit controls the length of the main body boom in accordance with the luffing angle of the main body boom detected by the boom luffing angle detection unit when the structure attitude detection unit detects that the attitude of the lower structure is the third stowed position, so as to avoid contact between the lower structure and the wire rope and the hook.

8. The main body side boom is equipped with a stopper that contacts the outer surface of the lower structure when the lower structure is in the retracted position. A portion of the lower structure forms a pin-supported portion that does not overlap the stopper laterally when the lower structure is in the second storage position, but overlaps the stopper laterally when the lower structure is in the third storage position. The structural holding member includes a storage pin that connects the stopper and the pinned support portion when the lower structure is in the third storage position, and the pin passes through the stopper. The crane according to claim 3, wherein the structural attitude detection unit determines that the retraction pin has penetrated the stopper and the pin-supported portion, and then detects that the attitude of the lower structure is the third retraction attitude.

9. The crane according to any one of claims 1 to 8, wherein the lower structure is capable of changing its posture between a working posture, which is a posture in which it is moved from below the main body boom, and a stowed posture, which is a posture in which it is positioned below the main body boom, and is an extension jib positioned on the tip side of the main body boom in the working posture.

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