Crane and its control method

Abstract

The present invention provides a crane and a control method thereof that can reduce the manufacturing cost of the crane while shortening the time required for the restoration of protective devices. [Solution] The crane 1 is equipped with a pressurizing unit 4 configured to supply fluid to the catenary device 2 and the protective device 3. The protective device 3 is equipped with a second sheave around which the cargo handling rope is wrapped, and a second fluid cylinder that moves the second sheave from its initial position to a protective position that reduces the tension of the cargo handling rope by extension and contraction. The pressurizing unit 4 includes a first control step in which it supplies fluid from a pump 4a that pressurizes the fluid to the catenary device 2 via a first circuit 4b, a second control step in which it supplies fluid from the pump 4a to the protective device 3 via a second circuit 4c, and a switching step in which it switches the circuit communicating with the pump 4a between the first circuit 4b and the second circuit 4c.

Description

Technical Field

[0001] The present invention relates to a crane including a catenary device and a protection device for protecting the crane from an overload occurring in a cargo handling rope, and more particularly to a crane and a control method thereof that can reduce the time required for the recovery work of the protection device while suppressing the manufacturing cost of the crane.

Background Art

[0002] The applicant has already proposed a configuration of a protection device for protecting a crane from an overload (snag load) occurring in a rope (see, for example, Patent Document 1). The protection device described in Patent Document 1 includes a sheave bracket that is tiltably supported by a structure of the crane, a sheave supported by the sheave bracket, and a shear pin that fixes the tilt of the sheave bracket. When an overload occurs in the rope, the shear pin breaks, and the sheave bracket tilts to reduce the tension of the rope.

[0003] When performing the recovery work of the protection device, it was necessary to return the sheave bracket to its original position with a chain block or the like and install a shear pin. Since high-altitude work by an operator was required, it took a relatively long time to recover the protection device. During the recovery work, the cargo handling work by the crane had to be stopped. In order to improve the cargo handling efficiency of the crane, it has been required to shorten the time required for the recovery work of the protection device.

[0004] On the other hand, the applicant has already proposed a configuration of a catenary device that supports a cargo handling rope (see, for example, Patent Document 2). The catenary device described in Patent Document 2 includes a land-side catenary, a sea-side catenary, and a moving rope wound around the two catenaries. The catenary device also includes another moving rope wound between the catenary and the trolley. The catenary has a configuration that follows the lateral movement of the trolley by the moving rope.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-933150 [Patent Document 2] Japanese Patent Publication No. 2012-201450 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] This invention was made in view of the above-mentioned problems, and its purpose is to provide a crane and a control method thereof that can reduce the time required for the restoration of protective devices while suppressing the manufacturing cost of the crane. [Means for solving the problem]

[0007] A crane for achieving the above objective is a catenary device having a first sheave around which a moving rope is draped together with a catenary, and a first fluid cylinder that moves the first sheave by extension and retraction to maintain the tension of the moving rope within a preset range, and a protective device that controls the tension of a cargo handling rope draped around a lifting device, wherein the crane is equipped with a pressurizing unit configured to supply fluid to the catenary device and the protective device, the protective device having a second sheave around which the cargo handling rope is draped, and a second fluid cylinder that moves the second sheave from an initial position to a protective position that reduces the tension of the cargo handling rope by extension and retraction, and the pressurizing unit is characterized by having a pump for pressurizing fluid, a first circuit for supplying fluid to the catenary device, a second circuit for supplying fluid to the protective device, and a switching mechanism for switching the circuit communicating with the pump between the first circuit and the second circuit.

[0008] A control method for achieving the above objective is a control method for a crane comprising a catenary device having a first sheave around which a moving rope is draped together with a catenary, and a first fluid cylinder that moves the first sheave by extension and contraction to maintain the tension of the moving rope within a preset range, and a protective device that controls the tension of a cargo handling rope draped around a lifting device, wherein the crane is pre-equipped with a pressurizing unit configured to supply fluid to the catenary device and the protective device, the protective device pre-equipped with a second sheave around which the cargo handling rope is draped, and a second fluid cylinder that moves the second sheave from an initial position to a protective position that reduces the tension of the cargo handling rope by extension and contraction, and the control method is characterized in that the pressurizing unit provides fluid from a pump that pressurizes the fluid to the catenary device via the first circuit, the pressurizing unit provides fluid from the pump to the protective device via the second circuit, and the pressurizing unit switches the circuit communicating with the pump between the first circuit and the second circuit. [Effects of the Invention]

[0009] According to the present invention, the sheave can be returned from the protected position to the initial position by supplying fluid from the pressurizing unit to the fluid cylinder. This is advantageous in reducing the time required for recovery work. Furthermore, by having the catenary device and the protective device share the pressurizing unit, the cost of introducing the protective device can be reduced. This is advantageous in reducing the manufacturing cost of the crane. [Brief explanation of the drawing]

[0010] [Figure 1] This is an explanatory diagram illustrating a crane from a side view. [Figure 2] This is an explanatory diagram illustrating a catenary device from an oblique view. [Figure 3] This is an explanatory diagram illustrating a protective device in a plan view. [Figure 4] This is an explanatory diagram illustrating the view from the direction of arrow AA in Figure 3. [Figure 5] This is an explanatory diagram illustrating the configuration of a pressurizing unit. [Figure 6] This is an explanatory diagram illustrating a modified example of Figure 5. [Figure 7] This is an explanatory diagram illustrating the direction of fluid movement when the protective device is activated. [Figure 8] This is an explanatory diagram illustrating the direction of fluid movement when a protective device is restored. [Modes for carrying out the invention]

[0011] The crane and its control method will be described below based on the embodiment shown in the figure. In the figure, the direction of travel of the crane is indicated by arrow y, the lateral direction perpendicular to this direction of travel is indicated by arrow x, and the vertical direction is indicated by arrow z.

[0012] As illustrated in Figure 1, crane 1 is equipped with a catenary device 2 and a protective device 3. Crane 1 is, for example, a container crane positioned on a quay for loading and unloading containers. Crane 1 is not limited to a container crane; it can be any crane equipped with a catenary device 2 and a protective device 3, such as an unloader for loading and unloading bulk cargo like coal, or a crane for shipping products that loads steel plates or coils.

[0013] In this embodiment, the protective device 3 is installed near the landward end of the girder 1a of the crane 1. The cargo handling rope R2, which is unwound from a drum installed in the machine room 1b, is fixed to the seaward end of the boom 1e via the protective device 3, trolley 1c, and lifting device 1d. The lifting device 1d moves in the vertical direction z as the cargo handling rope R2 is wound up and unwound by the drum. In Figure 1, for illustrative purposes, the cargo handling rope R2 stretched in a position shaded by the girder 1a and boom 1e is shown with a dashed line. The path along which the cargo handling rope R2 is routed and the location where the protective device 3 is installed are not limited to those described above. The protective device 3 only needs to be installed in the middle of the cargo handling rope R2 that is routed around the crane 1.

[0014] As illustrated in FIG. 2, the catenary device 2 has a land-side catenary 2a, a sea-side catenary 2b, and a moving rope R1 wound around the two catenaries 2a and 2b. The catenary device 2 also has another moving rope R1' stretched between the two catenaries 2a and 2b and the trolley 1c.

[0015] The catenary device 2 has a first sheave 2c around which the moving rope R1 is wound together with the catenaries 2a and 2b, and a first fluid cylinder 2d that moves the first sheave 2c by expansion and contraction to maintain the tension of the moving rope R1 within a preset range. Further, the crane 1 has a pressurizing unit 4 that supplies fluid to the first fluid cylinder 2d of the catenary device 2. In this embodiment, the first sheave 2c, the first fluid cylinder 2d, and the pressurizing unit 4 are installed near the land-side end of the gantry 1a. The catenary device 2 also has a pair of moving ropes R1, a first sheave 2c, and a first fluid cylinder 2d arranged side by side in the traverse direction x.

[0016] The catenaries 2a and 2b traverse at half the speed of the trolley 1c in conjunction with the traverse of the trolley 1c in the traverse direction x. By traversing in conjunction with the trolley 1c, the catenaries 2a and 2b can support the handling rope R2 at an appropriate position. When the first fluid cylinder 2d is supplied with fluid from the pressurizing unit 4, it generates a constant force in the contracting direction. As a result, the tension of the moving rope R1 is maintained constant. Even if the moving rope R1 elongates due to aging deterioration, the tension of the moving rope R1 is maintained constant by the contraction of the first fluid cylinder 2d. Since no sag occurs in the moving rope R1, the catenaries 2a and 2b can accurately follow the trolley 1c and traverse.

[0017] The configuration of the catenary device 2 is not limited to the above. The catenary device 2 only needs to have at least the first sheave 2c and the first fluid cylinder 2d. The catenary device 2 can adopt the configuration of a known catenary device.

[0018] As illustrated in FIGS. 3 and 4, the protection device 3 has a configuration for controlling the tension of the cargo handling rope R2 wound around the sling 1d. The protection device 3 has a second sheave 3a around which the cargo handling rope R2 is wound, and a second fluid cylinder 3b that moves the second sheave 3a from the initial position P1 to the protection position P2 where the tension of the cargo handling rope R2 is reduced by expansion and contraction. In this embodiment, as illustrated in FIG. 3, four cargo handling ropes R2 are paid out from the drum and stretched on the crane 1. The four cargo handling ropes R2 are each wound around the second sheave 3a of the protection device 3.

[0019] As illustrated in FIG. 4, the second sheave 3a is supported by a sheave bracket 3c. The sheave bracket 3c is composed of members extending in the vertical direction z. The sheave bracket 3c is supported by the structure of the crane 1 near the center in the vertical direction z. The sheave bracket 3c is supported so as to be tiltable about the traveling direction y as the central axis.

[0020] One end of the second fluid cylinder 3b is fixed near the upper end of the sheave bracket 3c in a tiltable state, and the other end is fixed to the structure of the crane 1 in a tiltable state. In this embodiment, as illustrated in FIG. 4, when the second fluid cylinder 3b is in the contracted state, the second sheave 3a is in the initial position P1, and when the second fluid cylinder 3b is in the extended state, the second sheave 3a is in the protection position P2. In FIG. 4, for the sake of explanation, the second sheave 3a, the sheave bracket 3c, and the second fluid cylinder 3b when the second sheave 3a is in the initial position P1 are shown by broken lines.

[0021] The direction in which the second fluid cylinder 3b is installed may be opposite in the traverse direction x. In this case, for example, the second fluid cylinder 3b is installed on the left side of the sheave bracket 3c illustrated in FIG. 4. When the second fluid cylinder 3b is in the extended state, the position of the second sheave 3a becomes the initial position P1, and when it is in the contracted state, the position of the second sheave 3a becomes the protection position P2.

[0022] As illustrated in Figure 4, when the second sheave 3a moves from its initial position P1 to its protective position P2, the tension of the cargo handling rope R2 decreases. Because the second sheave 3a moves in a direction that approaches the trolley 1c, the cargo handling rope R2 becomes slack.

[0023] The sheave bracket 3c is not an essential component of the protective device 3. A configuration in which the second sheave 3a is directly mounted on the second fluid cylinder 3b is also acceptable.

[0024] As illustrated in Figures 3 and 4, the crane 1 has a pressurizing unit 4 that supplies fluid to the second fluid cylinder 3b of the protective device 3. This pressurizing unit 4 is the same as the pressurizing unit 4 that supplies fluid to the first fluid cylinder 2d of the catenary device 2. In this embodiment, the pressurizing unit 4 is fixed to the upper surface of the girder 1a.

[0025] As illustrated in Figure 5, the crane 1 is equipped with a pressurizing unit 4 that is configured to supply fluid to the catenary device 2 and the protective device 3. In other words, the crane 1 is configured so that fluid is supplied to both the catenary device 2 and the protective device 3 from a single pressurizing unit 4.

[0026] The pressurizing unit 4 includes a pump 4a for pressurizing the fluid, a first circuit 4b for supplying fluid to the catenary device 2, a second circuit 4c for supplying fluid to the protective device 3, and a switching mechanism 4d for switching the circuit communicating with the pump 4a between the first circuit 4b and the second circuit 4c. In Figure 5, the area included in the pressurizing unit 4 is enclosed by a dashed line for illustrative purposes.

[0027] The first circuit 4b connecting the pump 4a and the catenary device 2 may consist of one pipe or two or more pipes. Similarly, the second circuit 4c connecting the pump 4a and the protective device 3 can consist of one or two or more pipes.

[0028] The switching mechanism 4d is composed of, for example, a solenoid valve. The operation of the solenoid valve switches the circuit communicating with the pump 4a from the first circuit 4b to the second circuit 4c. The switching mechanism 4d is not limited to a solenoid valve; it can be configured to connect one of the first circuit 4b and the second circuit 4c to the pump 4a and close the other. It is desirable that the closed circuit be configured to maintain pressure through the switching mechanism 4d.

[0029] The fluid supplied from the pressurizing unit 4 to the catenary device 2 and the protective device 3 is, for example, oil. In this case, the first fluid cylinder 2d and the second fluid cylinder 3b are hydraulic cylinders, and the pump 4a is a hydraulic pump. The type of fluid is not limited to the above, and other fluids such as air or water may be used. The first fluid cylinder 2d, the second fluid cylinder 3b, and the pump 4a are selected to be appropriate equipment according to the type of fluid.

[0030] Next, the control method for crane 1 will be explained. When crane 1 performs cargo handling operations, fluid is supplied from the pressurizing unit 4 to the catenary device 2. Specifically, the pressurizing unit 4 supplies fluid from the pump 4a that pressurizes the fluid to the catenary device 2 via the first circuit 4b (hereinafter sometimes referred to as the first control step S10). The first control step S10 is a control step for controlling the catenary device 2.

[0031] The first control step S10 maintains a constant tension in the moving rope R1. Because no slack occurs in the moving rope R1, the catenaries 2a and 2b can accurately follow the traverse movement of the trolley 1c. The crane 1 may have a configuration in which the first control step S10 is executed at all times during operation, such as during cargo handling.

[0032] If an overload occurs on the cargo handling rope R2 and the protective device 3 is activated, the protective device 3 is then reset. At this time, the crane 1 switches the circuit in which the pressurizing unit 4 communicates with the pump 4a between the first circuit 4b and the second circuit 4c (hereinafter sometimes referred to as the switching step S30). Specifically, the switching mechanism 4d is activated to switch the circuit in which the pump 4a communicates from the first circuit 4b to the second circuit 4c. The switching mechanism 4d may be switched by the operator or by control by a control mechanism or the like.

[0033] After the switching step S30, the pressurizing unit 4 supplies fluid from the pump 4a to the protective device 3 via the second circuit 4c (hereinafter sometimes referred to as the second control step S20). The second control step S20 is a control step for controlling the protective device 3.

[0034] As illustrated in Figure 4, fluid is supplied from the pump 4a of the pressurizing unit 4 to the second fluid cylinder 3b via the second circuit 4c, causing the second fluid cylinder 3b to contract and the second sheave 3a to return from the protected position P2 to the initial position P1. The fluid supply from the pressurizing unit 4 to the protective device 3 completes the recovery operation of the protective device 3. In Figures 3 and 4, the second circuit 4c is shown as a dashed line for illustrative purposes.

[0035] When the protective device 3 is activated, the crane 1 suspends cargo handling operations. Subsequently, the trolley 1c will not move until the recovery operation of the protective device 3 is completed. Therefore, the supply of fluid to the catenary device 2 is unnecessary until the recovery operation is completed. In other words, the first control step S10 for controlling the catenary device 2 is not executed. Therefore, it becomes possible to supply fluid from the pressurizing unit 4 to the protective device 3. The switching step S30 switches between the first control step S10 for controlling the catenary device 2 and the second control step S20 for controlling the protective device 3, and the first control step S10 and the second control step S20 are not executed simultaneously.

[0036] With this configuration, the crane 1 can return the second sheave 3a from the protected position P2 to the initial position P1 by supplying fluid from the pressurizing unit 4 to the protective device 3 during the recovery operation. This eliminates the need for workers to perform work at height. This is advantageous in reducing the time required for the recovery operation of the protective device 3.

[0037] With this configuration, crane 1 can supply fluid to both the catenary device 2 and the protective device 3 from a single pressurizing unit 4. Crane 1 does not need to have separate pressurizing units 4 corresponding to the catenary device 2 and the protective device 3. If crane 1 is already equipped with the catenary device 2 and pressurizing unit 4, the protective device 3 can be introduced without adding a new pressurizing unit 4. This is advantageous in reducing the cost of introducing the protective device 3 to crane 1. Also, when manufacturing a new crane 1, it is sufficient to install one pressurizing unit 4 for both the catenary device 2 and the protective device 3. This is advantageous in reducing the manufacturing cost of crane 1.

[0038] As illustrated in Figure 6, the pressurizing unit 4 may include a control mechanism 4e that controls the pump 4a and the switching mechanism 4d, and a sensor 4f that monitors the pressure of the first fluid cylinder 2d of the catenary device 2. In this embodiment, when the value of the sensor 4f is below a preset threshold, the control mechanism 4e activates the pump 4a and connects the pump 4a to the first circuit 4b via the switching mechanism 4d to supply fluid from the pump 4a to the first fluid cylinder 2d (hereinafter sometimes referred to as the supply step S11). When the value of the sensor 4f exceeds the threshold, the pump 4a is stopped (hereinafter referred to as the stop step S12). In this embodiment, the control mechanism 4e is connected to the sensor 4f, the pump 4a, and the switching mechanism 4d by wired or wireless signal lines. In Figure 6, the signal lines are shown as dashed lines for illustrative purposes.

[0039] Sensor 4f consists of, for example, a pressure sensor installed in the first circuit 4b. The installation location of the pressure sensor is not limited to the above; it may also be installed in the catenary device 2 or the first fluid cylinder 2d.

[0040] Sensor 4f may consist of a tension sensor that measures the tension of the moving rope R1. This tension sensor can indirectly monitor the pressure of the first fluid cylinder 2d by measuring the tension of the moving rope R1. The pressurizing unit 4 may have multiple pressure sensors, multiple tension sensors, or a combination thereof.

[0041] The operating and stopped states of pump 4a mean switching the current state to operating or stopped, regardless of past states. When pump 4a is set to the operating state, if pump 4a was stopped immediately before, pump 4a is activated, and if pump 4a was operating immediately before, pump 4a is maintained in operation. Similarly, when pump 4a is set to the stopped state, if pump 4a was stopped immediately before, pump 4a is maintained in a stopped state, and if pump 4a was operating immediately before, pump 4a is stopped.

[0042] When crane 1 performs cargo handling operations, catenaries 2a and 2b move traversely along the traverse direction x together with trolley 1c. When crane 1 is in operation, the first control step S10, which controls the catenary device 2, is executed. At this time, sensor 4f constantly monitors the pressure of the first fluid cylinder 2d.

[0043] In this embodiment, the first control step S10 includes a supply step S11 in which, when the value of the sensor 4f is less than or equal to a preset threshold, the pump 4a is put into an operating state and fluid is supplied to the first fluid cylinder 2d of the catenary device 2 via the first circuit 4b, and a stop step S12 in which, when the value of the sensor 4f exceeds the threshold, the pump 4a is put into a stopped state.

[0044] When the moving rope R1 stretches and its tension decreases, fluid is supplied to the first fluid cylinder 2d by the supply step S11. In the supply step S11, the tension of the moving rope R1 increases due to the expansion and contraction of the first fluid cylinder 2d. Specifically, the first fluid cylinder 2d contracts, for example, due to the supply of fluid, thereby increasing the tension of the moving rope R1. The orientation in which the first fluid cylinder 2d is installed may be reversed in the lateral direction x. In this case, fluid is supplied to the first fluid cylinder 2d by the supply step S11, causing the first fluid cylinder 2d to expand and increasing the tension of the moving rope R1.

[0045] The stopping step S12 stops the pump 4a. The pressure in the first fluid cylinder 2d is maintained, and the tension in the moving rope R1 is maintained. The stopping step S12 may also have a configuration that closes the first fluid cylinder 2d and the first circuit 4b. This makes it easier to maintain the pressure of the fluid inside the first fluid cylinder 2d, etc.

[0046] This configuration allows the pump 4a of the pressurizing unit 4 to operate intermittently. This eliminates the need for a cooling mechanism required when the pump 4a is operated continuously. This is advantageous for reducing the manufacturing cost of the pressurizing unit 4.

[0047] This configuration allows for the suppression of fluid temperature rise through intermittent operation of pump 4a. This makes it easier to avoid problems caused by fluid temperature rise, such as cavitation. It also improves the operational stability of catenary device 2 and protective device 3. This is advantageous for improving the operational stability of crane 1.

[0048] As illustrated in Figure 6, the pressurizing unit 4 may have a reserve tank 4g for storing the fluid discharged from the protective device 3. The reserve tank 4g is, for example, a rectangular parallelepiped tank. The reserve tank 4g is located, for example, inside the pressurizing unit 4. The installation location of the reserve tank 4g is not limited to this, and it may be fixed to the upper surface of the second fluid cylinder 3b of the protective device 3, as illustrated in Figures 3 and 4. The reserve tank 4g may also be installed on other structures of the crane 1, such as the girder 1a.

[0049] Next, the second control step S20 for controlling the protective device 3 will be described. As illustrated in Figure 1, when the crane 1 attempts to lift the ship 5 and a container that has not been released from its fastening, an overload occurs in the cargo handling rope R2. When an overload occurs, the crane 1 makes an emergency stop to hoist up the cargo handling rope R2. Because there is a delay in stopping the hoisting up of the cargo handling rope R2, the cargo handling rope R2 remains hoisted up by a certain amount even after the emergency stop command is issued. At this time, the tension of the cargo handling rope R2 increases rapidly. When an overload occurs in the cargo handling rope R2 as described above, the second control step S20 for controlling the protective device 3 is executed.

[0050] As illustrated in Figure 4, when the tension of the cargo handling rope R2 increases, the second sheave 3a, in its initial position P1, is subjected to a force pulling it to the right in Figure 4. This force is transmitted to the second fluid cylinder 3b via the sheave bracket 3c. The second fluid cylinder 3b is subjected to a force in the direction of extension.

[0051] As illustrated in Figure 7, the second fluid cylinder 3b has a first chamber 7 on the rod side and a second chamber 8 on the cap side, with the piston 6 as the boundary. Both the first chamber 7 and the second chamber 8 are filled with fluid. In this embodiment, the protective device 3 has a connecting pipe 9 that connects the first chamber 7 and the second chamber 8.

[0052] When rod 10 is subjected to a force in the direction of extension, the protective device 3 is activated. At this time, the pressure inside the second chamber 8 decreases as piston 6 moves. As the pressure in the second chamber 8 decreases, fluid is supplied from the reserve tank 4g to the second fluid cylinder 3b. In Figure 7, for illustrative purposes, the direction in which rod 10 is subjected to force is indicated by a white arrow, and the direction of fluid movement is indicated by an arrow.

[0053] As the piston 6 moves, the pressure inside the first chamber 7 increases. When the pressure in the first chamber 7 exceeds a preset threshold, the relief valve 11 located in the connecting pipe 9 is opened. The fluid then moves from the first chamber 7 to the second chamber 8 via the connecting pipe 9.

[0054] The second chamber 8 has a larger volume than the first chamber 7 by the amount corresponding to the rod 10. Since the volume is insufficient with only the fluid moving from the first chamber 7 to the second chamber 8 via the connecting pipe 9, the pressure inside the second chamber 8 drops. The portion of the fluid shortage in the second chamber 8 is supplemented by fluid supplied from the reserve tank 4g. Even in a configuration where fluid moves from the first chamber 7 to the second chamber 8, fluid also moves from the reserve tank 4g to the second chamber 8.

[0055] As fluid moves to the second fluid cylinder 3b, the second fluid cylinder 3b extends. At this time, the second sheave 3a moves from its initial position P1 to its protected position P2. In other words, the second control step S20 includes an operation step S21 that moves the second sheave 3a from its initial position P1 to its protected position P2 by moving fluid between the second fluid cylinder 3b and the reserve tank 4g.

[0056] The reserve tank 4g may be included in the protective device 3 instead of the pressurizing unit 4. In this case, no fluid will be moved between the second fluid cylinder 3b and the pressurizing unit 4 during the operation step S21.

[0057] With this configuration, the tension of the cargo handling rope R2 can be reduced by the activation of the protective device 3. This prevents problems such as damage to the crane 1 caused by excessive load being transmitted from the cargo handling rope R2 to the structure of the crane 1.

[0058] In the operation step S21, the fluid may be supplied from the pump 4a of the pressurizing unit 4 to the second chamber 8 of the second fluid cylinder 3b. In this case, when an overload occurs, the pump 4a is activated and fluid is supplied from the pump 4a to the second fluid cylinder 3b. However, the configuration in which the operation step S21 is performed without using the pump 4a of the pressurizing unit 4 allows for a faster response speed of the protection device 3 because there is no need to wait for the pump 4a to start up. This is advantageous for protecting the crane 1.

[0059] As illustrated in Figure 6, the control mechanism 4e may be configured to operate the pump 4a and connect the pump 4a to the second circuit 4c by a switching mechanism 4d, thereby supplying fluid from the pump 4a to the second fluid cylinder 3b.

[0060] As illustrated in Figure 8, when the protective device 3 is restored, fluid is supplied from the pump 4a to the first chamber 7 of the second fluid cylinder 3b via the second circuit 4c. The piston 6 moves due to the increase in pressure in the first chamber 7. The fluid in the second chamber 8 is pressurized and moves to the reserve tank 4g. This causes the second fluid cylinder 3b to contract. The second sheave 3a moves from the protected position P2 to the initial position P1. Thus, the restoration of the protective device 3 is completed. In other words, the second control step S20 has a restoration step S22 in which the pump 4a becomes operational and fluid is supplied from the pump 4a to the second fluid cylinder 3b of the protective device 3 via the second circuit 4c. In this embodiment, the second control step S20 has an operation step S21 that moves the second sheave 3a to the protected position P2 and a restoration step S22 that moves the second sheave 3a to the initial position P1.

[0061] After the recovery step S22 is completed, the pressurizing unit 4 communicates with the catenary device 2 via the switching step S30. The crane 1 resumes cargo handling operations while executing the first control step S10.

[0062] With this configuration, the protective device 3 can be restored by the operation of the pressurizing unit 4. This is advantageous in reducing the time required for the restoration of the protective device 3. [Explanation of Symbols]

[0063] 1 Crane 1a Garda 1b Machine room 1c Trolley 1d sling 1e Boom 2. Catenary Device 2a Land-side catenary 2b Ocean side catenary 2c First Sheave 2d First fluid cylinder 3 Protective device 3a Second Sheave 3b Second fluid cylinder 3c Sheave Bracket 4 Pressurization Unit 4a Pump 4b First circuit 4c Second circuit 4D switching mechanism 4e Control mechanism 4f detection 4g Reserve Tank 5 Ships 6 pistons 7 Room 1 8 Second room 9 Communication piping 10 rods 11 Relief valve x transverse direction y Direction of travel z Vertical direction R1 Moving Rope R2 Cargo handling rope P1 initial position P2 protection position S10 First control step S11 Supply Step S12 Stop step S20 Second control step S21 Operation Step S22 Recovery Steps S30 Switching Step

Claims

1. A crane equipped with a catenary device having a first sheave around which a moving rope is draped together with the catenary, and a first fluid cylinder that moves the first sheave by extension and contraction to maintain the tension of the moving rope within a preset range, and a protective device that controls the tension of a cargo handling rope draped around a lifting device, The system includes a pressurizing unit configured to supply fluid to the catenary device and the protective device, The protective device comprises a second sheave around which the cargo handling rope is wrapped, and a second fluid cylinder that moves the second sheave from its initial position to a protective position that reduces the tension of the cargo handling rope by extension and contraction. The pressurizing unit is characterized by comprising a pump for pressurizing a fluid, a first circuit for supplying fluid to the catenary device, a second circuit for supplying fluid to the protective device, and a switching mechanism for switching the circuit communicating with the pump between the first circuit and the second circuit.

2. The pressurizing unit includes a control mechanism that controls the pump and the switching mechanism, and a sensor that monitors the pressure of the first fluid cylinder. The crane according to claim 1, wherein the control mechanism has a configuration that, when the value of the sensor is less than or equal to a preset threshold, the pump is put into operation and the switching mechanism connects the pump and the first circuit to supply fluid from the pump to the first fluid cylinder, and when the value of the sensor exceeds the threshold, the pump is put into a stopped state.

3. The pressurizing unit has a control mechanism that controls the pump and the switching mechanism, The crane according to claim 1 or 2, wherein the control mechanism is configured to operate the pump and connect the pump and the second circuit by the switching mechanism to supply fluid from the pump to the second fluid cylinder.

4. A control method for a crane comprising a catenary device having a first sheave around which a moving rope is draped together with the catenary, and a first fluid cylinder that moves the first sheave by extension and contraction to maintain the tension of the moving rope within a preset range, and a protective device that controls the tension of a cargo handling rope draped around a lifting device, The crane is equipped with a pressurizing unit configured to supply fluid to the catenary device and the protective device. The protective device includes a second sheave around which the cargo handling rope is wrapped, and a second fluid cylinder that moves the second sheave from its initial position to a protective position that reduces the tension of the cargo handling rope by extension and contraction. The pressurizing unit provides fluid from a pump that pressurizes the fluid to the catenary device via the first circuit in a first control step, The pressurizing unit supplies fluid from the pump to the protective device via the second circuit in a second control step, A control method characterized in that the pressurizing unit includes a switching step for switching the circuit communicating with the pump between the first circuit and the second circuit.

5. The pressurizing unit is equipped with a sensor that monitors the pressure of the first fluid cylinder, The first control step is, A supply step in which, when the value of the sensor is below a preset threshold, the pump becomes operational and fluid is supplied from the pump to the first fluid cylinder of the catenary device via the first circuit, The control method according to claim 4, further comprising a stop step in which the pump enters a stopped state when the value of the sensor exceeds the threshold.

6. The second control step is, The control method according to claim 4 or 5, further comprising a recovery step in which the pump becomes operational and fluid is supplied from the pump to the second fluid cylinder of the protective device via the second circuit.

7. The pressurizing unit has a reserve tank pre-connected to the second fluid cylinder, The second control step is, The control method according to claim 6, further comprising an operating step of moving the second sheave from the initial position to the protective position by moving fluid between the second fluid cylinder and the reserve tank.

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