JPH042519B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting overload of a load lifted by a crane, and particularly to an overload detection device that takes into account variations in the weight of the jib of the crane.

[Prior art]

Generally, for cranes, etc., the rated lifting load is determined based on the crane's mechanical strength and overturning stability, and according to the undulation angle (or working radius) of the crane's jib.

By the way, in conventional overload detection devices for cranes, the heave angle of the jib is detected, and a rated load signal (load due to the jib and cargo) corresponding to this jib heave angle is generated from a so-called rated load curve storage unit. By comparing this rated load signal with a signal corresponding to the actually measured lifting load, an overload condition is detected and an alarm device or the like is activated.

[Problem that the invention seeks to solve]

By the way, with a crane, tension is generated in the rope supporting the jib due to the hanging load and the jib's own weight, but when the length of the jib is changed depending on the work conditions,
Alternatively, when the jib is replaced due to the end of its service life, the weight of the jib may change due to the weight tolerance of the pipe materials constituting the jib or variations in the amount of welding of the pipes. Therefore, with an overload detection device that detects whether or not there is an overload based on the rated load calculated in advance and the measured load of both the jib and the cargo, the accuracy of the alarm point of the load due to the actual cargo is extremely poor. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an overload detection device that corrects the dispersion between a pre-calculated value and an actual measured value of a crane jib, and has extremely high accuracy in detecting a warning point due to an overload caused by an actual load. It is in.

[Means for solving problems]

The present invention is an overload detection device for detecting an overload load of a crane. When comparing the actual jib dead weight determined by the jib with the second tension determined for each jib heave angle or working radius based on the measured load, the jib's heave angle or Normalize the difference between the third tension determined for each working radius and the fourth tension determined for each undulation angle or working radius only by the actual measured jib weight, and calculate this normalized difference. is used to correct either the first tension or the second tension, and after this correction, if the second tension becomes larger than the first tension, an overload condition is detected and an alarm is issued. This is a crane overload detection device characterized by:

〔Example〕

The present invention will be described below based on examples. First, a crane 1 to which an overload detection device according to the present invention is applied will be described with reference to FIG. It is supported by rope 4. Furthermore, a pulley 5' equipped with a hook is suspended from the jib 3 via a wire rope 5.
A load 6 is suspended from the pulley 5', and the load 6 can be raised or lowered by winding up or lowering the wire rope 5. Furthermore, the jib 3 can be rotated horizontally by the rotation of the upper revolving structure 2, and the jib 3 can wind up the wire rope 4.
By unwinding, the undulation angle θ can be changed. Therefore, when a load is not suspended, a tension (moment) corresponding to the undulation angle θ is applied to the wire rope 4 due to the weight of the jib 3, and when the load 6 is suspended, the weight of the jib 3 and the weight of the load 6 are applied to the wire rope 4. A tension corresponding to the undulation angle θ due to the weight is applied to the wire rope 4. A load detector (not shown) is attached to the base end or middle of the wire rope 4 to measure the tension of the wire rope 4, and an angle measuring device is attached to the jib 3 to measure the undulation angle θ of the jib 3. (not shown) is provided.

Therefore, in such a crane 1, if the moment applied to the jib 3 (that is, the tension applied to the wire rope 4) is too large, the crane will fall or break. ), the rated load of the cargo 6 that can be lifted is predetermined, but conventionally,
This rated load is compared with the value measured by the load detector above to determine whether or not there is an overload, so if the jib's own weight increases or decreases, the actual load due to the cargo is overloaded. There was a tendency for the judgment to be inaccurate.

Next, referring also to FIG. 2, an overload detection device according to the present invention will be explained.

The load detector 7 mentioned above is connected to the calculation comparison section 9. Further, the angle detector 8 is connected to a first storage section 10, a second storage section 11, and a third storage section 12.
0, 11 and 12 are connected to the arithmetic comparison section 9. A mode setting device 13 and an alarm device 14 are connected to this arithmetic comparison section 9.

A standard value of the tension due to the self-weight of the standard jib 3 according to the heave angle θ is calculated in advance and input into the second storage unit 11 . That is, the tension due to the jib's own weight under the crane design conditions (F ₂ , third tension)
The relationship between this and the jib's heave angle is input. (Hereinafter, this tension will be referred to as a standard value. For example, the information shown in FIG. 3b is input).

The third storage unit 12 also stores the standard value and the heave angle θ (or working radius) of the jib 3 of the crane 1.
The total value of tension (F ₃ ) due to the maximum allowable load that can be lifted (hereinafter referred to as rated load) corresponding to (hereinafter simply referred to as first tension = rated tension)
is input and stored (for example, the information shown in FIG. 3c is input). The mode setter 13 sets the arithmetic and comparison section 9 between a read mode and a normal mode. Set the reading mode from the mode setting device 13, change the heave angle (θ) of the jib 3, and adjust the self-weight of the jib 3 while the load 6 is not hoisted on the jib 3 of the crane 1 shown in Fig. 1. A load detector 7 measures the tension (F ₁ , fourth tension) applied to the wire rope 4 in relation to the undulation angle θ. And this tension F ₁
is input to the arithmetic comparison section 9 (for example, Fig. 3a
The relationship between the undulation angle θ and the tension F ₁ as shown in is input. ). On the other hand, the third tension (F ₂ ) is read out from the second storage section 11 in accordance with the undulation angle (θ) detected by the angle detector 8 at this time, and is input to the arithmetic comparison section 9. The calculation comparison section 9 calculates the third tension (F ₂ )
and the fourth tension (F ₁ ), a correction value (α) shown in equation (1) is calculated in correspondence with the undulation angle (θ), and this correction value (α) is stored in the first storage unit 10. Remember.

α=1F ₁ /F ₂ ...(1) Next, the normal mode is set from the mode setting device 13, and the load 6 is hoisted onto the jib 3 of the crane 1.
The load detector 7 measures the tension (F ₄ ) (second tension) applied to the wire rope 4 in accordance with the heave angle θ (or working radius) of the jib 3 and inputs it to the calculation comparison section 9. .

At this time, the heave angle θ of the jib 3 is measured by the angle detector 8, and the angle signal (θ) of the angle detector 8 is stored in the first, second, and third storage units 10, 11 as shown in the figure. and 12, each storage unit 1
Corresponding to the angle signals 0, 11, and 12, correction values α and tensions F ₂ and F ₃ corresponding to the heave angle θ of the jib 3 are input to the computation/comparison unit 9, respectively.

First, the arithmetic comparison section 9 multiplies the tension (F ₂ ) represented by the standard value of the jib 3 by the correction value (α) to obtain the correction tension (αF ₂ ). moreover,
As shown in equation (2), the rated tension (F ₃ ) and the corrected tension (αF ₂ ) are subtracted to obtain the tension (F ₅ ).

F ₅ =F ₃ −αF ₂ ...(2) As is clear from equations (1) and (2), F ₁ =
If F ₂ , this crane has a rated tension (F ₃ )
can be added. If F ₁ <F ₂ , only a tension smaller than the rated tension (F ₃ ) can be applied. Also, if F ₁ > F ₂ , the rated tension (F ₃ )
This means that a greater tension can be applied.

After that, the calculation comparison section 9 calculates the measured tension (F ₄ )
and tension (F ₅ ), and when the relationship shown in equation (3) is satisfied, an alarm signal is sent to the alarm device 14.

F ₄ ≧F ₃ −αF ₂ ...(3) In this way, no matter what type of jib is installed, the difference between the tension due to the jib's own weight (F ₁ ) and the standard value (F ₂ ) is normalized. This normalized difference is used to correct the allowable maximum load that can be applied to the crane, that is, the total value (the jib's own weight and the maximum load due to the load), so even if the jib configuration is changed, the There is no need for correction, and furthermore, it is possible to suppress variations in the alarm point (the amount of suspended load that issues an alarm) due to variations in the jib's own weight, etc., and it is possible to improve the accuracy of the alarm point.

By the way, the arithmetic comparison unit 9 first adds the corrected tension (αF ₂ ) and the measured tension (F ₄ ) as shown in equation (4), calculates the tension (F ₆ ), and calculates the rated tension (F ₃ ) F ₆ = F ₄ + αF ₂ ...(4) is compared with the tension (F ₆ ), and when the relationship shown in the fifth equation is established, an alarm signal is sent to the alarm 14. good.

F ₃ ≦F ₄ + αF ₂ ...(5) [Effects of the Invention] As explained above, in the present invention, the tension due to the own weight of the jib attached to a crane etc. and the tension due to the predetermined jib own weight (standard value ), and then use this normalized difference to correct the tension (rated tension) due to the predetermined jib weight and load applied to the crane, and calculate the corrected jib weight and load. By setting the alarm to be issued based on the tension caused by , the hassle of re-correction is eliminated.

[Brief explanation of drawings]

Fig. 1 is a diagram schematically showing an example of a crane in which the overload detector according to the present invention is used, Fig. 2 is a block diagram showing the overload detector according to the present invention, and Fig. 3 a is a diagram showing the weight of the jib. Figures 3b and 3c are diagrams showing the tension applied to the wire rope in relation to the undulation angle in relation to the undulation angle.
It is a figure which shows the relationship between an undulation angle and tension memorized by a 3rd storage part. 1... Crane, 2... Upper revolving structure, 3... Jib, 4, 5... Wire rope, 6... Luggage, 7...
... Load detector, 8 ... Angle detector, 9 ... Calculation comparison section, 10 ... First storage section, 11 ... Second storage section, 12 ... Third storage section, 13 ... Mode setting device, 14... Alarm.

Claims (1)

[Claims] 1 A crane that has a jib with one end pivotally attached to a revolving structure and a wire rope that supports the other end of the jib, and that changes the undulation angle of the jib by winding and unwinding the wire rope. The overload detection device is used for detecting the overload load of the crane according to the tension applied to the wire rope. The first tension (F ₃ ) acting on the wire rope, and the second tension acting on the wire rope determined for each jib heave angle or working radius by the actual jib dead weight and the measured load determined by actual measurements. When comparing the tension (F ₄ ) with the third tension (F ₂ ) acting on the wire rope, which is determined for each undulation angle or working radius of the jib by the predetermined jib's own weight, A correction value (α=1−(F ₁ /F ₂ )) is calculated using the fourth tension (F ₁ ) acting on the wire rope, which is determined for each jib angle or working radius only by the jib's own weight. is calculated, and a correction calculation is performed by multiplying either the first tension or the second tension by the correction value, and after the correction calculation, the second tension becomes equal to the first tension. A crane overload detection device characterized by detecting an overload condition and issuing an alarm when the tension exceeds the tension.