JP3962812B2 - Method and apparatus for reducing electric shock in crane and crane having electric shock reducing function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for reducing electric shock in a crane, and a crane having an electric shock reduction function, and more specifically, electric shock in a crane that prevents an operator engaged in a staking operation or the like from being electric shocked. The present invention relates to a mitigation method and apparatus, and a crane having an electric shock mitigation function.
[0002]
It should be noted that the hoisting operation refers to an operation of hanging a crane wire or rope on the load when the load is lifted by the crane.
[0003]
BACKGROUND OF THE INVENTION AND PRIOR ART
Conventionally, when a large crane such as a rough terrain crane is used in the vicinity of a medium wave broadcasting station, a high voltage is applied to the hook of the crane due to radio interference that the crane acts as a medium wave receiving antenna. There was a problem that the worker engaged in the balling work might be shocked by being induced.
[0004]
In order to solve such problems, there have been proposed methods such as applying an insulator to a crane hook or attaching a grounding wire to the crane hook.
[0005]
In addition to the method described above, a method of reducing the high voltage of the crane hook by extending the antenna wire to the crane boom and adjusting the inductance and capacitance connected in series with the antenna wire is proposed. Has been.
[0006]
However, the method of applying an insulator to the hook has a problem that a sufficient effect cannot be obtained for rainwater conduction during rainy weather work.
[0007]
Further, in the method of attaching the grounding wire to the hook, it is necessary to attach the grounding wire to the hook every time work is performed, so that the work of attaching the grounding wire to the hook becomes complicated, and the workability is inferior.
[0008]
Furthermore, in the method of extending the antenna wire to the boom of the crane, there is a problem that it is not easy to attach the antenna wire to the boom when it is necessary to extend and retract the boom during the operation.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the various problems of the prior art as described above, and the object of the present invention is to prevent radio interference when a crane is used near a medium wave broadcasting station. By reducing the voltage induced in the hook of the crane permanently, the electric shock mitigation method for a crane and its It is an object of the present invention to provide a crane having a device and a lightning mitigation function.
[0010]
Further, an object of the present invention is to provide an electric shock mitigation method and apparatus in a crane that can be easily applied to a crane that can be moved frequently on a work site, such as a mobile crane having a boom telescopic function, and It is intended to provide a crane with a lightning mitigation function.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an electric shock mitigation method and apparatus for a crane according to the present invention and a crane equipped with an electric shock mitigation function are provided by changing the voltage induced in the hook of the crane by resonance and changing the resonance frequency of the crane. It is intended to reduce.
[0012]
In other words, in the present invention, an insulator is inserted between the crane body and the ground to form a ground capacitance, and a parallel resonant circuit is formed by an inductance connected in parallel to the ground. This changes the resonance characteristics of the crane.
[0013]
That is, a high voltage is induced in the hook under resonance conditions due to radio wave interference that the crane acts as a medium-wave receiving antenna. In such a case, if the crane's vehicle body impedance is increased by adding a parallel resonance circuit, the crane's resonance characteristics will change greatly, reducing the voltage induced on the hook, and making the ball work, etc. Electric shock to workers engaged in
[0014]
That is, the invention of claim 1 of the present invention is a lightning mitigation method in a crane for reducing the shock at the crane caused by interference of the medium wave broadcast, the first conductor to the vehicle body and the upper surface of the crane And forming a ground capacitance by inserting an insulator between the reinforcing plate arranged on the ground surface and providing an inductance for parallel resonance with the ground capacitance, and the resonance frequency of the crane. Is to change.
[0015]
The invention according to claim 2 of the present invention is the invention according to claim 1 of the present invention , wherein the second conductor is inserted between the reinforcing plate and the ground surface .
[0016]
Further, the invention according to claim 3 of the present invention is an electric shock mitigation device for a crane for reducing electric shock in a crane caused by radio wave interference of a medium wave broadcast, wherein the outrigger float of the crane or the ground surface of a crawler belt is provided. In order to resonate in parallel with the ground capacitance formed by the insulator disposed on the side , the reinforcing plate disposed between the insulator and the ground surface, the first conductor formed on the upper surface, and the insulator The crane is in contact with the ground surface only through the insulator and the reinforcing plate, and one terminal of the inductance is connected to the outrigger float or crawler belt of the crane, and the other terminal of the inductance. It is so as to form a parallel resonance circuit connected to said first conductor formed on the upper surface of the reinforcing plate It is intended.
[0017]
According to a fourth aspect of the present invention, in the third aspect of the present invention , the second conductor is inserted between the reinforcing plate and the ground surface. .
[0018]
In addition, the invention according to claim 5 of the present invention is such that the electric shock mitigation device for a crane according to any one of claims 3 or 4 of the present invention is attached to the bottom surface of the outrigger float of the crane. It is fixed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of a crane provided with an electric shock mitigation method and apparatus and an electric shock mitigation function in a crane according to the present invention will be described in detail with reference to the accompanying drawings.
[0020]
In the following drawings and the description thereof, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.
[0021]
FIG. 1 is a conceptual configuration explanatory diagram of a crane having an electric shock mitigation function according to an example of an embodiment of the present invention.
[0022]
The crane shown in FIG. 1 is a rough terrain crane that is one of mobile cranes. The rough terrain crane 10 includes a vehicle body 14 having wheels 12 for moving to a desired work site, and a vehicle body 14. A boom 16 installed, a jib 18 extending from the boom 16, a wire 20 suspended from a tip 18a of the jib 18, a hook 22 attached to the tip of the wire 20, and a crane work In this case, an outrigger 24 for supporting the entire rough terrain crane 10 and an outrigger float 26 which is a contact member with the ground surface side of the outrigger 24 are provided.
[0023]
Here, in the rough terrain crane 10 described above, an electric shock mitigation device (hereinafter simply referred to as “electric shock mitigation device”) 100 in the crane is disposed between the outrigger float 26 and the ground surface. More specifically, the electric shock mitigation device 100 is disposed between the outrigger float 26 and the reinforcing plate 30 laid on the ground surface. The reinforcing plate 30 is formed by covering an aluminum plate 30b on the upper surface of a wooden reinforcing plate main body 30a.
[0024]
The electric shock mitigation device 100 includes a plate-like insulating plate 102 made of an insulating material such as acrylic, and a variable inductance 104.
[0025]
Here, the insulating plate 102 is disposed between the outrigger float 26 and the ground surface, specifically, between the outrigger float 26 and the aluminum plate 30b of the reinforcing plate main body 30a.
[0026]
On the other hand, the variable inductance 104 is configured such that one terminal 104a thereof can be connected to the outrigger float 26 and the other terminal 104b can be connected to the ground surface side. More specifically, one terminal 104a of the variable inductance 104 is configured to be connectable to the outrigger float 26, and the other terminal 104b of the variable inductance 104 is configured to be connectable to the aluminum plate 30b of the reinforcing plate 30.
[0027]
In the above configuration, when carrying out crane work using the rough terrain crane 10, the outrigger 24 is extended to support the rough terrain crane 10, and the outrigger float 26 of the outrigger 24 is brought into contact with the ground surface side. become.
[0028]
At this time, the reinforcing plate 30 is disposed on the ground surface, and the electric shock reducing device 100 is further disposed on the reinforcing plate 30 so that the bottom surface of the outrigger float 26 and the insulating plate 102 of the electric shock reducing device 100 are in contact with each other. Thus, the outrigger float 26 is disposed so as to come into contact with the ground surface side through the electric shock reducing device 100 and the reinforcing plate 30.
[0029]
The terminal 104 a of the variable inductance 104 of the electric shock reducing device 100 is connected to the outrigger float 26, and the other terminal 104 b of the variable inductance 104 of the electric shock reducing device 100 is connected to the aluminum plate 30 b of the reinforcing plate 30.
[0030]
By the way, when the total length of the boom 16, jib 18 and wire 20 of the rough terrain crane 10 becomes about ¼ of the wavelength of the medium wave coming to the rough terrain crane 10, resonance occurs and the hook 22 has a high voltage. Will be induced.
[0031]
Here, FIG. 2 shows a simple equivalent circuit of the rough terrain crane 10 shown in FIG. Under resonance conditions, if the angular frequency of the medium wave coming to the rough terrain crane 10 is ω,
ωL ₁ = 1 / ωC ₁
The resonance conditions are as follows.
[0032]
At this time, the earth capacitance of the rough-terrain crane 10 using the shock reducing apparatus 100 and C _2, when the connected inductance value between the vehicle body 14 and ground and L _2,
ωL ₂ = 1 / ωC ₂
When is established, parallel resonance occurs and the induced current of the rough terrain crane 10 is reduced, so that the voltage induced to the hook 22 can be reduced.
[0033]
Therefore, by setting the inductance value of the variable inductance 104 of the electric shock mitigation device 100 according to the angular frequency of the medium wave coming to the rough terrain crane 10 according to ω, the voltage induced to the hook 22 is reduced, and the It is possible to reduce the risk of electric shock of workers engaged in work.
[0034]
That is, by using the electric shock mitigation device 100, the resonance characteristics of the rough terrain crane 10 can be changed, the voltage induced in the rough terrain crane 10 by a medium wave is reduced, and electric shock to the worker is reduced. be able to.
[0035]
Moreover, since the electric shock mitigation device 100 has a simple structure and can be easily moved, it can be easily applied to a crane that can move frequently on the work site, such as a mobile crane having a boom telescopic function. Can be applied to.
[0036]
In addition, when the electric shock mitigation device 100 is used, since a large impedance is added between the vehicle body 14 and the ground, the induced current is also reduced and the malfunction prevention of the overload prevention device provided in the crane is prevented. Will also contribute.
[0037]
Next, an experimental result by the present inventor will be described. In this experiment, a rough terrain crane having a lifting load of 50 tons was used as the rough terrain crane 10. The height of the body 14 of the rough terrain crane 10 is about 3.5 m, the length of the boom 16 is 39 m, the angle of the boom is 80 °, and the length of the jib 18 is 14.5 m. Yes, the angle of the jib 18 is 35 °, the length of the wire 20 is about 49 m, and the ground height of the hook 22 is 1 m.
[0038]
In the rough terrain crane 10 having the above-described dimensions, first, when the electric shock reducing device 100 is not used, that is, a wooden reinforcing plate (an aluminum plate is disposed on the upper surface of the reinforcing plate) between the outrigger float 26 and the ground surface. The voltage of the hook 22 was about 2000 Vpp in the normal working state with the cover.
[0039]
On the other hand, in the configuration shown in FIG. 1, an acrylic plate having a thickness t of 10 mm is used as the insulating plate 102, the value of the variable inductance 104 is set to 91 μH, and one terminal 104a of the variable inductance 104 is connected to the outrigger float 26. When the other terminal 104b of the variable inductance 104 was connected to the aluminum plate 30b of the reinforcing plate 30, the voltage of the hook 22 could be reduced to about 1500 Vpp.
[0040]
In the experiment described above, there is an influence of the ground capacitance of the vehicle body 14 of the rough terrain crane 10 and the resistance of the ground, and it is considered that the effect is as described above. A reduction effect was observed.
[0041]
For improving the sharpness Q characteristics of the parallel resonant circuit, for example, a conductor such as a wire mesh 200 is laid on the ground surface where the crane of the rough terrain crane 10 is installed as shown in FIG. The sharpness Q characteristic can be further improved.
[0042]
The embodiment described above may be modified as shown in the following (1) to (3).
[0043]
(1) In the above-described embodiment, the rough terrain crane 10 and the electric shock mitigation device 100 are configured separately, but it is needless to say that the present invention is not limited to this.
[0044]
That is, the rough terrain crane provided with the electric shock mitigation function may be configured by fixedly arranging the electric shock mitigation device 100 on the bottom surface 26a of the outrigger float 26 of the rough terrain crane 10.
[0045]
At this time, one terminal 104 a of the variable inductance 104 of the electric shock reducing device 100 may be fixedly connected to the outrigger float 26.
[0046]
(2) In the above-described embodiment, the case where the electric shock reducing device 100 is used for the rough terrain crane 10 as a mobile crane has been described. However, the present invention is not limited to this.
[0047]
That is, as the mobile crane, for example, the electric shock reducing device 100 may be used for a crawler crane. When the lightning mitigation device 100 is used in a crawler crane, the lightning mitigation device 100 may be disposed between the crawler belt (crawler belt) 300 and the aluminum plate 30b of the reinforcing plate 30, as shown in FIG.
[0048]
At this time, one terminal 104 a of the variable inductance 104 of the electric shock reducing device 100 may be connected to the crawler belt 300, and the other terminal 104 b may be connected to the aluminum plate 30 b of the reinforcing plate 30.
[0049]
(3) The above-described embodiment and the modifications shown in (1) to (2) above may be used in appropriate combination.
[0050]
【The invention's effect】
Since the present invention is configured as described above, it is possible to permanently reduce radio interference when the crane is used in the vicinity of a medium-wave broadcasting station, and the voltage induced on the hook of the crane. As a result, it is possible to greatly reduce the risk of electric shock of workers engaged in balling work.
[0051]
In addition, since the present invention is configured as described above, it can be applied to a crane that can frequently move on the work site, such as a mobile crane having a boom telescopic function. There is an excellent effect of being able to.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a conceptual configuration of a crane having an electric shock mitigation function according to an example of an embodiment of the present invention.
FIG. 2 is a simple equivalent circuit of the crane shown in FIG.
3 is a conceptual structural explanatory diagram showing a state in which a conductor such as a wire mesh is laid on the ground surface where the crane is installed in the crane shown in FIG. 1. FIG.
FIG. 4 is an explanatory diagram of a conceptual configuration of a crane having an electric shock mitigation function according to another embodiment of the present invention.
[Explanation of symbols]
10 Rough terrain crane 12 Wheel 14 Car body 16 Boom 18 Jib 20 Wire 22 Hook 24 Outrigger 26 Outrigger float 30 Reinforcement plate 30a Reinforcement plate body 30b Aluminum plate 100 Electric shock mitigation device 102 Insulation plate 104 Variable inductance 104a Terminal 104b Terminal 200 Wire net 300 Crawler belt

Claims (5)

In the method of reducing electric shock in a crane for reducing electric shock in a crane caused by radio wave interference of medium wave broadcasting,
In order to form a ground capacitance by inserting an insulator between the crane body and a reinforcing plate disposed on the ground surface with a first conductor formed on the top surface, and to resonate in parallel with the ground capacitance An electric shock mitigation method for a crane, characterized by changing the resonance frequency of the crane. In the electric shock mitigation method in the crane according to claim 1,
A method for reducing electric shock in a crane, wherein a second conductor is inserted between the reinforcing plate and the ground surface . In the electric shock mitigation device in the crane for reducing electric shock in the crane caused by radio wave interference of the medium wave broadcast,
An insulator disposed on the ground surface side of the outrigger float or crawler belt of the crane;
A reinforcing plate disposed between the insulator and the ground surface and having a first conductor formed on an upper surface;
Having an inductance for parallel resonance with a ground capacitance formed by the insulator,
The crane contacts the ground surface only through the insulator and the reinforcing plate,
One terminal of the inductance is connected to the outrigger float or crawler belt of the crane, and the other terminal of the inductance is connected to the first conductor formed on the upper surface of the reinforcing plate to form a parallel resonance circuit. Electric shock mitigation device in a crane characterized by the above. In the electric shock mitigation device in the crane according to claim 3,
A lightning mitigation device for a crane, wherein a second conductor is inserted between the reinforcing plate and the ground surface . In a crane equipped with an electric shock mitigation function to reduce electric shock caused by radio wave interference of medium wave broadcasting,
The crane provided with the electric shock reduction function characterized by fixing the electric shock reduction apparatus in the crane of any one of Claim 3 or Claim 4 to the bottom face of the outrigger float of a crane.

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