Protective device and its control method

Abstract

The present invention provides a protective device and a control method thereof that can shorten the time required for recovery work. [Solution] The fluid cylinder 4a moves the sheave 3 from an initial position P1 to a protective position P2 that reduces the tension of the rope R by expansion and contraction; a reserve tank 4b that supplies fluid to the fluid cylinder 4a when it is in operation; an operating pipe 4c that connects the reserve tank 4b and the fluid cylinder 4a to move the fluid; a pressurizing unit 4d that supplies fluid to the fluid cylinder 4a when it is restored; and a restoration pipe 4e that connects the pressurizing unit 4d and the fluid cylinder 4a to move the fluid. The fluid cylinder 4a is supplied from the reserve tank 4b to the fluid cylinder 4a via the operating pipe 4c, and the restoration pipe 4e is supplied from the pressurizing unit 4d to the fluid cylinder 4a via the restoration pipe 4e.

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a protection device for protecting a crane from an overload generated in a rope and a control method thereof, and more particularly to a protection device capable of shortening the time required for recovery work and a control method thereof.

Background Art

[0002] The applicant has already proposed a configuration of a protection device for protecting a crane from an overload (snag load) generated 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 a 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 workers 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.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] This invention was made in view of the above-mentioned problems, and its purpose is to provide a protective device and a control method thereof that can shorten the time required for recovery work. [Means for solving the problem]

[0006] A protective device for achieving the above objective comprises a sheave around which a rope is wrapped, and a moving mechanism for moving the sheave in a direction that reduces the tension of the rope, wherein the moving mechanism is characterized by comprising a fluid cylinder that moves the sheave from an initial position to a protective position that reduces the tension of the rope by expansion and contraction, a reserve tank that supplies fluid to the fluid cylinder when in operation, operating piping that connects the reserve tank and the fluid cylinder to move the fluid, a pressurizing unit that supplies fluid to the fluid cylinder when restored, and restoration piping that connects the pressurizing unit and the fluid cylinder to move the fluid.

[0007] A control method for achieving the above objective is a control method for a protective device comprising a sheave around which a rope is wrapped, and a moving mechanism for moving the sheave in a direction that reduces the tension of the rope, wherein the moving mechanism pre-installs a fluid cylinder that moves the sheave from an initial position to a protective position that reduces the tension of the rope by extension and contraction, a reserve tank that supplies fluid to the fluid cylinder when operating, an operating pipe that connects the reserve tank and the fluid cylinder to move the fluid, a pressurizing unit that supplies fluid to the fluid cylinder when restoring, and a restoration pipe that connects the pressurizing unit and the fluid cylinder to move the fluid, and further comprises an operating step in which fluid is supplied from the reserve tank to the fluid cylinder via the operating pipe, and a restoration step in which fluid is supplied from the pressurizing unit to the fluid cylinder via the restoration pipe. [Effects of the Invention]

[0008] 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. [Brief explanation of the drawing]

[0009] [Figure 1] This is an explanatory diagram illustrating a crane equipped with protective devices, shown in a side view. [Figure 2] This is an explanatory diagram illustrating a protective device in a plan view. [Figure 3] This is an explanatory diagram illustrating the view from the direction of arrow AA in Figure 2. [Figure 4] This is an explanatory diagram illustrating the state of the protective device when it is in operation. [Figure 5] This is an explanatory diagram illustrating the direction of fluid movement during operation. [Figure 6] This is an explanatory diagram illustrating the direction of fluid movement during recovery. [Modes for carrying out the invention]

[0010] The protective device 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 traverse direction perpendicular to this direction of travel is indicated by arrow x, and the vertical direction is indicated by arrow z.

[0011] As illustrated in Figure 1, the protective device 1 is installed, for example, on a crane 2 that is positioned on a quay and loads and unloads containers. The protective device 1 is not limited to this and can be applied to any crane on which a rope R is stretched. In this embodiment, the protective device 1 is installed near the landward end of the girder 2a. The rope R, which is unwound from a drum installed in the machine room 2b, is fixed to the seaward end of the boom 2e via the protective device 1, trolley 2c, and lifting device 2d. The lifting device 2d moves in the vertical direction z as the rope R is wound up and unwound by the drum. In Figure 1, for illustrative purposes, the rope R stretched in a position that is in the shadow of the girder 2a and boom 2e is shown with a dashed line. The path along which the rope R is stretched and the location where the protective device 1 is installed are not limited to the above. The protective device 1 only needs to be installed in the middle of the rope R that is stretched around the crane 2.

[0012] As illustrated in Figures 2 and 3, the protective device 1 comprises a sheave 3 around which the rope R is hoisted, and a moving mechanism 4 that moves the sheave 3 in a direction that reduces the tension of the rope R. As illustrated in Figure 2, in this embodiment, four ropes R are unwound from a drum and tensioned onto the crane 2. Each of the four ropes R is hoisted onto the sheave 3 of the protective device 1.

[0013] As illustrated in Figure 3, the sheave 3 is supported by a sheave bracket 5. The sheave bracket 5 is composed of a member extending in the vertical direction z. The sheave bracket 5 is supported by the structure of the crane 2 near its center in the vertical direction z. The sheave bracket 5 is supported so as to be tiltable about the travel direction y as its central axis.

[0014] The moving mechanism 4 includes a fluid cylinder 4a that moves the sheave 3 from its initial position P1 to a protective position P2 that reduces the tension of the rope R by extension and retraction, a reserve tank 4b that supplies fluid to the fluid cylinder 4a when it is in operation, an operating pipe 4c that connects the reserve tank 4b and the fluid cylinder 4a to move the fluid, a pressurizing unit 4d that supplies fluid to the fluid cylinder 4a when it is restored, and a restoration pipe 4e that connects the pressurizing unit 4d and the fluid cylinder 4a to move the fluid. In Figures 2 and 3, the restoration pipe 4e is shown as a dashed line for illustrative purposes.

[0015] The fluid cylinder 4a is fixed at one end in a tiltable state near the upper end of the sheave bracket 5, and at the other end in a tiltable state to the structure of the crane 2. In this embodiment as illustrated in FIG. 3, when the fluid cylinder 4a is in the contracted state, the position of the sheave 3 is the initial position P1. As illustrated in FIG. 4, when the fluid cylinder 4a is in the extended state, the position of the sheave 3 is the protection position P2. In FIG. 4, for the sake of explanation, the sheave 3, the sheave bracket 5, and the fluid cylinder 4a when the sheave 3 is at the initial position P1 are shown by dashed lines.

[0016] The direction in which the fluid cylinder 4a is installed may be opposite in the lateral direction x. In this case, for example, the fluid cylinder 4a is installed on the left side of the sheave bracket 5 illustrated in FIG. 3. When this fluid cylinder 4a is in the extended state, the position of the sheave 3 is the initial position P1, and when in the contracted state, the position of the sheave 3 is the protection position P2.

[0017] As illustrated in FIG. 4, when the sheave 3 moves from the initial position P1 to the protection position P2, the tension of the rope R decreases. Since the sheave 3 moves in the direction approaching the trolley 2c, the rope R becomes slack.

[0018] The fluid cylinder 4a is constituted by, for example, a hydraulic cylinder. The fluid cylinder 4a is not limited to this, and may have a configuration that expands and contracts using the pressure of other fluids such as air or water. The sheave bracket 5 is not an essential component of the protection device 1. A configuration in which the sheave 3 is directly installed on the fluid cylinder 4a may also be used.

[0019] The reserve tank 4b has a configuration for storing the fluid corresponding to the fluid cylinder 4a. The reserve tank 4b is constituted by, for example, a rectangular parallelepiped tank. In this embodiment as illustrated in FIG. 3, the reserve tank 4b is fixed to the upper surface of the fluid cylinder 4a. The installation position of the reserve tank 4b is not limited to the above. The reserve tank 4b may be installed on other structures of the crane 2 such as the girder 2a, or may be installed inside the pressurizing unit 4d.

[0020] The actuating pipe 4c is connected at one end to the reserve tank 4b and at the other end to the fluid cylinder 4a. The actuating pipe 4c is composed of, for example, a steel pipe with an inner diameter of 100 mm and a total length of 300 mm. However, the actuating pipe 4c is not limited to this, and the inner diameter, total length, and constituent material are appropriately changed according to the capacity of the fluid cylinder 4a and the like.

[0021] The pressurizing unit 4d has a pump for pressurizing and conveying the fluid corresponding to the fluid cylinder 4a and a tank for storing the fluid. The pressurizing unit 4d can supply the fluid to the fluid cylinder 4a by operating the pump. In the embodiments illustrated in FIGS. 2 and 3, the pressurizing unit 4d is fixed to the upper surface of the girder 2a.

[0022] The recovery pipe 4e is connected at one end to the pressurizing unit 4d and at the other end to the fluid cylinder 4a. The recovery pipe 4e is composed of, for example, a pipe with an inner diameter of 10 mm and a total length of 7000 mm. The recovery pipe 4e is composed of a rubber hose, a steel pipe, or a combination thereof. When the relative position between the pressurizing unit 4d and the fluid cylinder 4a changes, the recovery pipe 4e has a configuration that can absorb the change in the relative position, such as a rubber hose, at least in part. However, the recovery pipe 4e is not limited to this, and the inner diameter, total length, and constituent material are appropriately changed according to the installation positions of the fluid cylinder 4a and the pressurizing unit 4d and the like.

[0023] Next, a control method for the protection device 1 will be described. As illustrated in FIG. 1, when the crane 2 attempts to lift a container that is not released from the ship 6, an overload occurs in the rope R. When an overload occurs, the crane 2 immediately stops winding the rope R. Since there is a delay in stopping the winding of this rope R, the rope R is wound up by a certain amount even after the emergency stop command is issued. At this time, the tension of the rope R rapidly increases.

[0024] As illustrated in Figure 4, when the tension of rope R increases, sheave 3, which is in its initial position P1, experiences a force pulling it to the right in Figure 4. This force is transmitted to the fluid cylinder 4a via the sheave bracket 5. The fluid cylinder 4a then experiences a force in the direction of extension.

[0025] As illustrated in Figure 5, the fluid cylinder 4a has a first chamber 10 on the rod side and a second chamber 11 on the cap side, with the piston 9 as the boundary. The first chamber 10 and the second chamber 11 are filled with fluid. In this embodiment, the moving mechanism 4 has a connecting pipe 4f that connects the first chamber 10 and the second chamber 11. The connecting pipe 4f may have the same inner diameter and constituent materials as, for example, the operating pipe 4c. Alternatively, the connecting pipe 4f may have the same inner diameter and constituent materials as, for example, the recovery pipe 4e.

[0026] When rod 8 is subjected to a force in the direction of extension, protective device 1 is activated. At this time, the pressure inside the second chamber 11 decreases as piston 9 moves. As the pressure in the second chamber 11 decreases, fluid is supplied from the reserve tank 4b to the fluid cylinder 4a via the operating pipe 4c (hereinafter sometimes referred to as the operating step). In Figure 5, for illustrative purposes, the direction in which rod 8 is subjected to force is indicated by a white arrow, and the direction of fluid movement is indicated by an arrow.

[0027] As the piston 9 moves, the pressure inside the first chamber 10 increases. When the pressure in the first chamber 10 exceeds a preset threshold, the relief valve 12 located in the connecting pipe 4f is opened. In the operation step of this embodiment, fluid moves from the first chamber 10 to the second chamber 11 via the connecting pipe 4f.

[0028] The second chamber 11 has a larger volume than the first chamber 10 by the amount corresponding to the rod 8. Since the volume is insufficient with only the fluid moving from the first chamber 10 to the second chamber 11 via the connecting pipe 4f, the pressure inside the second chamber 11 drops. The portion of the fluid shortage in the second chamber 11 is supplemented by fluid supplied from the reserve tank 4b. Even in a configuration where fluid moves from the first chamber 10 to the second chamber 11, fluid also moves from the reserve tank 4b to the second chamber 11.

[0029] As the fluid moves in and out of the fluid cylinder 4a, the fluid cylinder 4a extends. At this time, the sheave 3 moves from its initial position P1 to its protected position P2. Since the tension in the rope R decreases, the transmission of overload from the rope R to the structure of the crane 2 can be suppressed. The crane 2 is protected from overload.

[0030] The reserve tank 4b may have an opening valve 13 (air breather) to maintain the internal pressure at atmospheric pressure. This prevents negative pressure from forming inside the reserve tank 4b when fluid moves from the reserve tank 4b to the second chamber 11. The opening valve 13 enables smooth fluid movement from the reserve tank 4b to the second chamber 11.

[0031] The configuration of the connecting pipe 4f is not an essential component of the moving mechanism 4. If the moving mechanism 4 does not have the connecting pipe 4f, the fluid in the first chamber 10 may be sent to, for example, the pressurizing unit 4d, or to a separately connected drain tank.

[0032] As illustrated in Figure 6, when restoring the protective device 1, fluid is supplied from the pressurizing unit 4d to the fluid cylinder 4a via the restoration piping 4e (hereinafter sometimes referred to as the restoration step). The pump of the pressurizing unit 4d operates, supplying pressurized fluid to the first chamber 10 via the restoration piping 4e. In Figure 6, for illustrative purposes, the direction in which the piston 9 receives force is indicated by a white arrow, and the direction of fluid movement is indicated by an arrow.

[0033] The recovery step may have a configuration in which fluid moves from the fluid cylinder 4a to the reserve tank 4b via the operating pipe 4c. As the piston 9 moves, the pressure inside the second chamber 11 increases, and the fluid in the second chamber 11 moves to the reserve tank 4b via the operating pipe 4c.

[0034] The moving mechanism 4 may have an overflow pipe 4g connecting the reserve tank 4b and the pressurizing unit 4d. When the amount of fluid inside the reserve tank 4b exceeds a predetermined amount, the fluid is returned to the pressurizing unit 4d via the overflow pipe 4g. The fluid returned to the pressurizing unit 4d is stored in a tank installed in the pressurizing unit 4d.

[0035] As the recovery step causes the fluid cylinder 4a to contract, the sheave 3 returns from the protected position P2 to the initial position P1. This completes the recovery operation of the protective device 1.

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

[0037] In this configuration, when the fluid cylinder 4a extends or retracts during operation, fluid is supplied from the reserve tank 4b to the fluid cylinder 4a. This is advantageous for improving the response speed of the moving mechanism 4 to external forces. The protective device 1 can achieve the response speed necessary to protect the crane 2 while reducing the time required for recovery work. The faster the protective device 1 responds to overload, the more it can avoid problems such as shocks occurring in the crane 2.

[0038] If the system is configured to supply fluid from the pressurizing unit 4d to the fluid cylinder 4a during operation, it would be necessary to start the pump of the pressurizing unit 4d after the tension of the rope R increases. Supplying fluid from the reserve tank 4b to the fluid cylinder 4a eliminates the need to start the pump, etc., and improves the response speed of the moving mechanism 4 compared to supplying fluid from the pressurizing unit 4d to the fluid cylinder 4a.

[0039] As illustrated in Figure 2, it is desirable that the reserve tank 4b be installed closer to the fluid cylinder 4a than the pressurizing unit 4d. In this embodiment, the pressurizing unit 4d is installed on the upper surface of the girder 2a, and the reserve tank 4b is installed on the upper surface of the fluid cylinder 4a. The reserve tank 4b is positioned closer to the fluid cylinder 4a than the pressurizing unit 4d, not only in the horizontal x and y directions but also in the vertical z direction.

[0040] Alternatively, the position where the operating pipe 4c connected to the reserve tank 4b is shorter than the recovery pipe 4e connected to the pressurizing unit 4d may be defined as being close to the fluid cylinder 4a. In this case, the distance to the fluid cylinder 4a is determined not by the distance based on the three-dimensional coordinates of the reserve tank 4b and the pressurizing unit 4d, but by the length including the arrangement of the operating pipe 4c and the recovery pipe 4e. When the operating pipe 4c is shorter than the recovery pipe 4e, the reserve tank 4b can be said to be in a position closer to the fluid cylinder 4a.

[0041] When the protective device 1 is activated, fluid is supplied from the reserve tank 4b to the fluid cylinder 4a via a relatively short operating pipe 4c.

[0042] This configuration allows fluid to be supplied to the fluid cylinder 4a from the reserve tank 4b, which is closer than the pressurizing unit 4d. This improves the speed at which fluid is supplied to the fluid cylinder 4a. In addition, since the operating pipe 4c is shorter than the recovery pipe 4e, resistance associated with fluid movement can be suppressed. The operating pipe 4c makes it easier to increase the flow velocity of the fluid passing through it. This is advantageous for improving the response speed of the moving mechanism 4.

[0043] With this configuration, when an overload occurs on the rope R, the fluid cylinder 4a can receive fluid in a relatively short time, and the sheave 3 can complete its movement to the protected position P2. This is advantageous in suppressing damage to the crane 2 due to overload.

[0044] The extension and retraction speed of the fluid cylinder 4a is less likely to cause problems even if it is slower during recovery compared to during operation. Therefore, during recovery, there is no problem with a configuration in which fluid is supplied to the fluid cylinder 4a from a pressurizing unit 4d located at a relatively distant position. Even if there is no space to install the pressurizing unit 4d near the fluid cylinder 4a, it is sufficient if only a reserve tank 4b, which is smaller than the pressurizing unit 4d, is installed near the fluid cylinder 4a. This is advantageous for improving the response speed when the protective device 1 is activated.

[0045] As illustrated in Figure 2, it is desirable that the operating pipe 4c be composed of a pipe with a larger inner diameter than the recovery pipe 4e. For example, the inner diameter of the operating pipe 4c can be 2 to 20 times larger than the inner diameter of the recovery pipe 4e.

[0046] This configuration makes it easier to increase the fluid flow rate through the operating pipe 4c. It also makes it easier to suppress the resistance generated in the fluid. This is advantageous for improving the response speed when the protective device 1 is activated.

[0047] If the reserve tank 4b is installed relatively close to the fluid cylinder 4a, the installation cost of the operating piping 4c can be reduced. Generally, installation costs increase when piping with a relatively large inner diameter is bent or otherwise positioned. The shorter the length of the piping with a relatively large inner diameter, the lower the installation cost can be. If the reserve tank 4b is directly fixed to the fluid cylinder 4a, the relative position to the reserve tank 4b does not change with the expansion and contraction of the fluid cylinder 4a, so the operating piping 4c can be made of steel pipe. Since there is no need to combine it with rubber tubing or the like to absorb changes in relative position, this is advantageous in reducing the manufacturing cost of the operating piping 4c.

[0048] It is desirable that the recovery piping 4e be composed of a pipe with a relatively small inner diameter. During recovery, the expansion and contraction speed of the fluid cylinder 4a does not need to be as fast as during operation. Therefore, the recovery piping 4e can be composed of a pipe with a smaller inner diameter than the operation piping 4c. This is advantageous in reducing the installation cost of the recovery piping 4e.

[0049] As illustrated in Figure 3, it is desirable that the reserve tank 4b be installed at a higher position than the fluid cylinder 4a. Specifically, it is desirable that the reserve tank 4b be installed directly above the fluid cylinder 4a. The installation position of the reserve tank 4b is not limited to directly above the fluid cylinder 4a, as long as it is at a higher position than the fluid cylinder 4a; it may also be fixed to the structure of the crane 2.

[0050] The fluid stored in the reserve tank 4b is more easily moved to the fluid cylinder 4a due to the effect of gravity.

[0051] This configuration allows for an improvement in the fluid velocity of the fluid moving from the reserve tank 4b to the fluid cylinder 4a during operation. This is advantageous for improving the response speed of the moving mechanism 4. If the reserve tank 4b is installed at a lower position than the fluid cylinder 4a, the negative pressure generated in the second chamber 11 during operation causes the fluid to move from the reserve tank 4b to the fluid cylinder 4a. If the reserve tank 4b is installed at a higher position than the fluid cylinder 4a, the fluid velocity can be improved due to the effect of gravity in addition to the negative pressure mentioned above.

[0052] The reserve tank 4b may have a configuration that pre-pressurizes the fluid inside it. This is advantageous for increasing the fluid flow velocity when the protective device 1 is activated, thereby improving the response speed of the moving mechanism 4. The pressurization of the reserve tank 4b can be performed, for example, from the pressurizing unit 4d via the overflow pipe 4g. [Explanation of symbols]

[0053] 1 Protective device 2 Cranes 2a Garda 2b Machine room 2c Trolley 2d sling 2e Boom 3 sieves 4 Moving mechanism 4a Fluid cylinder 4b Reserve Tank 4c Actuation piping 4D pressurization unit 4e Piping for restoration 4F Connecting piping 4g overflow piping 5 Sheave bracket 6 ships 8 rods 9 pistons 10 Room 1 11 Second room 12 Relief valves 13 Opening valve x transverse direction y Direction of travel z Vertical direction R Rope P1 initial position P2 protection position

Claims

1. A protective device comprising a sheave around which a rope is wrapped, and a moving mechanism for moving the sheave in a direction that reduces the tension of the rope, The protective device is characterized by comprising: a fluid cylinder that moves the sheave from an initial position to a protective position that reduces the tension of the rope by extension and retraction; a reserve tank that supplies fluid to the fluid cylinder when in operation; operating piping that connects the reserve tank and the fluid cylinder and moves the fluid; a pressurizing unit that supplies fluid to the fluid cylinder when restored; and restoration piping that connects the pressurizing unit and the fluid cylinder and moves the fluid.

2. The protective device according to claim 1, wherein the reserve tank is configured to be installed closer to the fluid cylinder than the pressurizing unit.

3. The protective device according to claim 1 or 2, wherein the operating piping is composed of piping with a larger inner diameter than the recovery piping.

4. The protective device according to claim 1 or 2, wherein the reserve tank is installed at a higher position than the fluid cylinder.

5. A control method for a protective device comprising a sheave around which a rope is wrapped, and a moving mechanism that moves the sheave in a direction that reduces the tension of the rope, The aforementioned moving mechanism includes a fluid cylinder that moves the sheave from its initial position to a protective position that reduces the tension of the rope by extension and retraction, a reserve tank that supplies fluid to the fluid cylinder when in operation, operating piping that connects the reserve tank and the fluid cylinder to move the fluid, a pressurizing unit that supplies fluid to the fluid cylinder when in recovery, and recovery piping that connects the pressurizing unit and the fluid cylinder to move the fluid, An operating step in which fluid is supplied from the reserve tank to the fluid cylinder via the operating piping, A control method characterized by comprising a recovery step in which fluid is supplied from the pressurizing unit to the fluid cylinder via the recovery piping.

6. The control method according to claim 5, wherein the recovery step is configured such that fluid moves from the fluid cylinder to the reserve tank via the operating piping.

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