JPS63127994A - Winding abnormal-load protective method of crane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for protecting a crane from abnormal hoisting loads, and particularly relates to a protection method effective in dealing with cases where the hoisting tension becomes an overload. TECHNOLOGY AND PROBLEMS] Conventionally, a container crane is used to, for example, unload containers from a container ship by suspending a spreader from wires at four corners and raising and lowering the spreader. With this type of container crane, when loading and unloading containers in the hold, there is a guide called a cell guide in the hold that allows the spreader to be hoisted up safely, so the spreader can be rolled up in the hold without being restricted by anything. It is believed that the top can be achieved. However, there are cases in which ships carry out special cargo handling operations that do not make effective use of cell guides, and different loads due to hull rolling and the like act on the ship, resulting in overload on the suspension wires.

In such a case, there was no protection device in the past, but the crane's electric motor protection device is activated, the crane hoisting operation is stopped by the brake, the crane and the container are directly connected, and the container is guided to the hold cell guide. If this was regulated, the load of the ship itself would be applied to the container, which would apply the load of the ship to the crane, leading to the risk of wire breakage.

The present invention focuses on the above-mentioned conventional problems and provides a method for protecting a crane from abnormal hoisting loads, which is safe and prevents wire breakage when an abnormal load such as a ship's load is applied to the crane. The purpose is to

[Means and effects for solving the problem] In order to achieve the above object, the abnormal load protection method for a crane according to the present invention defines the tension range when hoisting the crane based on the rated maximum load, wire strength, etc. The maximum allowable crane load is divided into three areas as a boundary load, and the crane brake is released when at least the crane hoisting tension exceeds the maximum allowable crane load.

With the above configuration, the range where the tension is applied is divided into three areas, and when the maximum area is reached, the braking action that has been applied up to that point is released, allowing the so-called spreader to descend according to the load. This eliminates cutting losses.

〔Example〕

Embodiments of the method for protecting a crane from abnormal hoisting loads according to the present invention will be described in detail with reference to the drawings.

First, as shown in FIG. 2, the container spreader 10 has hanging wires 12 (12
A, 12B, 12C, 12D),
It is hoisted up or hoisted down by a motor (not shown). Each wire 12 has a load cell 14 (14A, 14B
, 14G, 14D) are installed so that the tension of each wire can be detected. The output from the load cell 14 is input to a control device 16, and based on signal processing by this control device 16, a brake (brake) for stopping operation is applied to the drive motor of the drum that winds up or lowers the wire 12.
(not shown) outputs a brake control signal.

FIG. 1 shows a method of performing signal processing by the control device 16 to protect against abnormal hoisting loads.

The control device 16 inputs the signal from the load cell 14, and the tension range obtained from this input signal is divided into three regions and each region is processed separately. In other words, basically, the tension applied to the wire 12 is detected, and if this detected value is in the region below the rated maximum load (first region), it exceeds the rated maximum load and the crane's allowable maximum load specified by the wire strength etc. The processing is different in each of the following three areas (second area) and when the crane exceeds the allowable maximum load (third area). In the region, the brake of the main winding device is operated, and in the third region, the brake is released.

First, the signal from the load cell 14 is expressed as a value when the tension applied to the wire at the time of hoisting the rated load is taken as 100%, and the values corresponding to each load cell are indicated by A, B, C, and D. , the boundary value between the second areas is A+B+C+D=
It is set as 105%. This is the rated load (100
Since it is not possible to stop the winding at 5%), the boundary value is set with a margin of 5%. In this case, A and B
+C10 indicates the 1-1 barrel tension applied to all the wires 12 when hoisting the rated load, but since the wire attachment positions for each wire 12A to 12D are at the four corners of the spreader 10, the eccentric load due to eccentricity must be taken into account. Therefore, the wire tension at each corner is A for A+B+C+D=105%.

When B, C, or D is 125%, it is treated equally as a boundary value between the first and second regions.

Next, the boundary value between the second area and the third area is A+B+C+D
= 150%. This value is determined in consideration of the fact that crane structural standards require a braking capacity of 150% or more, and the stability, mechanical strength, etc. of the crane. Also, the value of 150% is for the total wire tension, and for each wire 12A to 12D.
, A, B, C or D is 1 considering the eccentric load.
A value of 70% is treated equally as a boundary value between the second and third regions. In particular, the value of 170% corresponds to the strength of wires 12A-12D.

In this way, the range of tension applied to the wires 12A to 12D is divided into three regions, and the following processing is performed depending on which region ff1M the detected wire tension is applied to.

First, the total tension of the wire A + B 〇 + D is 105%
In the following cases, or when the tension of each wire is 125% or less, so-called normal operation is performed and the container is engaged in cargo handling work. However, when the total load approaches the rated maximum load, it is necessary to notify the crane operator that it has reached the danger zone, so a warning is issued to the operator when the total load exceeds A + B + C + D = 90%. (step 100).

Next, when it is detected that the load cell signal exceeds the boundary value between the first and second regions and is in the second region, the brake of the main winding device is closed to stop the hoisting operation. At this time, it is determined whether the main winding protection circuit provided separately is normal or not by checking whether the overcurrent relay is activated or not (step 200).
), if it is operating, the lowering operation will be stopped as an abnormality (
Step 210) 1 If it is not operating, it is assumed to be normal and only the hoisting operation is stopped (step 220), and the hoisting operation by the driver is enabled to be performed (step 230).

By performing the lowering operation at the discretion of the driver,
It becomes possible to avoid abnormal loads.

Furthermore, if the overcurrent relay is operating and the detected wire tension reaches the third region because the abnormal load cannot be avoided due to the driver's hoisting operation, then the wire tension is located in the third region. It is determined whether or not the time period continues for a certain period of time (step 310). Step 310 is A+B+C+D>150% or A, B, C of the load cell signal.
Or, it determines whether D > 170% continues for 0.5 seconds or more, and if the signal duration is 0.5 seconds or more, it is determined that the signal correctly represents an abnormal load state. If the signal duration is less than 0.5 seconds, it is assumed that an abnormal condition has appeared instantaneously and the brake is not released (step 320). 330).

As the wire tension increases and reaches the second region, the brake of the crane main hoisting device is activated to at least stop hoisting the container. When a load is applied and the wire tension increases to reach the third region, the brake is released, thereby preventing abnormal load movements from being applied to the crane, eliminating the risk of wire breakage and damage to the crane.

Note that when the brake is released in the third region, the hanging container descends together with the spreader 10 (step 340), but a safety circuit is provided to prevent danger associated with the descent. In other words, when the suspended load starts to fall due to the brake release operation, the load cell signal is detected and this is set to the set value (for example, A+B+C+D=150%).
(step 400), and if it is lower than the set value, the brake is closed (step 410).
. Also, if it is greater than the set value, the maximum brake opening time is set by a timer, and when the continuation signal of the load cell signal is greater than the set time, the process is sent to step 410 to close the brake, and the brake is closed when the continuation signal of the load cell signal is greater than the set time. Sometimes, the process returns to step 400 (step 420).
At the same time, the speed detector detects the descending speed, and when the falling speed is greater than the value set as the critical speed, the brake is closed at step 410, and when it is smaller, the process returns to step 400 (step 430). ). Furthermore, an emergency stop button dedicated to the abnormal hoisting load protection circuit is installed, and if the button is operated to proceed to step 410 and the button is not operated, the process returns to step 400.

Here, the total tension (A+B+C+D) based on the signals from the load cells 14A to 14D is displayed on a load meter in the crane operator's cab (step 500).

〔Effect of the invention〕

As explained above, according to the present invention, the range of tension applied to the crane wire is divided into three regions.

If there is enough tension to cause the wire to break, this is detected and the brake is released.
It is possible to carry out safe cargo handling work without fear of wire breakage.

[Brief explanation of the drawing]

Figure 1 is a flowchart showing the protection method of the embodiment;
The figure is a configuration diagram of the tension detection means.

Claims (1)

[Claims] (1) Divide the tension range when hoisting the crane into three areas with the maximum rated load and the maximum permissible crane load specified from wire strength, etc. as boundary loads, and at least the crane hoisting tension exceeds the maximum permissible crane load. A method for protecting a crane from abnormal hoisting loads, the method comprising: releasing a crane brake when