JPH01148461A - Arc saw cutting device - Google Patents

Abstract

PURPOSE:To prevent cutting capacity of an arc saw from being deteriorated due to overheat of a shaft by providing channels of lubricating oil to the shaft for a rotating electrode on an arc sawing device for underwater cutting and circulating the lubricating oil in bearing chambers at both ends of the shaft through said channels to cool the shaft. CONSTITUTION:The discoid electrode 1 is rotated at a high speed by the shaft 3 under water and an arc with the low voltage and a high electric current is generated between said electrode 1 and a material to be cut to cut the material to be cut by the arc. In this case, the high current for cutting is also carried to the shaft 3 to which the rotating electrode 1 is fitted and the shaft 3 itself attains the high temperature by Joule heat and accidents such as burning of bearings 23 and damage of a casing 2 for the shaft are caused. In order to prevent these accidents, many channels 101 are provided to the shaft 3 and the lubricating oil in the bearing chambers 24 in front and in rear of the shaft 3 is circulated through the channels 101 and the shaft 3 is cooled by the lubricating oil and the abnormal temperature-rise of the shaft 3 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an arc saw cutting device used when cutting steel materials such as a nuclear reactor pressure vessel underwater, for example in a nuclear power plant.

(Prior Art) For example, in a nuclear power plant, equipment such as a reactor pressure vessel reaches the end of its life after long-term use.

In that case, it will be necessary to completely dismantle and remove equipment such as the reactor pressure vessel. At this time, it is necessary to cut the structure underwater, and the following cutting methods are available for such work. That is, gas cutting methods, methods combining gas cutting methods and gouging methods, electrode water jet cutting methods, plasma cutting methods, electrical discharge machining methods, and the like. However, with this method, there is a problem in cutting underwater steel materials such as thick plates and pipes that have been activated in a nuclear reactor. For example, in the case of the gas cutting method described above, if there is a cladding of austenitic stainless steel, cutting becomes impossible. In addition, a method that combines gas cutting and gouging has not yet been put to practical use, and even if it were, the cutting speed would be slow and there would be a lot of by-products during cutting. It is not suitable for cutting radioactive materials.

Based on this actual situation, a cutting method called arc saw cutting has been considered. The outline will be explained below with reference to FIG. Reference numeral 1 in FIG. 4 indicates a rotating electrode, and this rotating electrode 1
is fixed to a shaft 3 rotatably installed within the casing 2. On the outer peripheral edge of this rotating electrode 1, a fifth
As shown in the figure, slits IA are formed at equal intervals in the circumferential direction, and the molten material (molten slag) is scraped out by the ζ noslits IA. The shaft 3 is connected to a hydraulic motor 4 installed outside the casing 2, and by driving the hydraulic motor 4, the rotating electrode 1 is rotated. A copper brush 5 is installed inside the casing 2 and on the outer periphery of the shaft 3.
is connected to one pole (-pole) of a DC power supply 7 via a cable 6. On the other hand, an object 9 to be cut is connected to the other pole (electrode) of the DC power source 7 via a cable 8.

The casing 2 is a piston 1 of a hydraulic cylinder mechanism 1o.
1, so that the slide casing 2 of the piston 1 slides in the direction toward and away from the object 9 to be cut. The hydraulic cylinder mechanism 1o is controlled by a servo system 12. That is, rotating electrode 1
The cutting current when cutting is performed by bringing the cable close to the object 9 to be cut is detected by an ammeter 13 inserted in the cable 6, and the detection signal is input to a current comparator 14. In addition to the above-mentioned detection signal, the current comparator 14 also receives the control panel 15
A preset control signal is input. The current comparator 14 compares these detection signals and control signals and outputs the difference therebetween to the serve system 12 as a difference signal. The serve system 12 operates the hydraulic cylinder mechanism 1 based on the difference signal of the engine.
The purpose is to keep the cutting current constant by controlling o.

Note that reference numeral 16 in the figure indicates an air inlet, through which compressed air is injected into the casing 2 to shield the power supply portion to the rotating electrode 1.

According to the above configuration, when cutting the object 9, first the hydraulic motor 4 is driven to rotate the rotary electrode 1, and the hydraulic cylinder mechanism 10 is driven to rotate the piston 1.
1 downward in the figure, and the rotating electrode 1 is placed on the object 9 to be cut.
approach. The rotating electrode 1 is approximately zero relative to the object to be cut.
．． An arc discharge is performed at a point located approximately 1 to 0.2 milliJ away, and a DC low voltage high current (voltage
The cutting work is performed by melting the object 9 with electrical energy of 0 V and a current of about 4000 A to 2000 OA, and removing melting slag by the slit IA.

Next, the structure of the head portion of the arc saw cutting device will be explained in detail with reference to FIG. FIG. 6 is a sectional view of the head part, and the rotating electrode 1 is fixed to the shaft 3 with a screw 21. The shaft 3 has both ends connected to the rollers 2>E? through an insulator 22. ) are supported by bearings 23 and 23, respectively.

These roller bearings 23.23 are installed in bearing chambers 24.24 formed in the casing 2, and the portion where the brush 5 is installed is a brush chamber 25. Reference numeral 26 in the figure indicates a sealing member. Lubricating oil is supplied into the bearing chamber 24 through an oil supply port 27, and the supplied lubricating oil is drained through an oil drain port 28. Note that the pressure of the air supplied through the air inlet I6 is higher than the pressure of the lubricating oil.

In the above configuration, for example, when performing cutting work, phenomena such as an abnormal decrease in rotational speed, seizure due to an abnormal temperature rise in the bearing 23, or cracks in a portion of the casing 2 may occur. These problems are caused by the fact that Joule heat is generated in the shaft 3 by supplying a large current to the rotating electrode 1, and the nuclear heat is stored without being cooled, resulting in an abnormally high temperature. by. The reduction in rotational speed as described above not only reduces the ability to discharge molten slag during cutting, but also may cause seizure of the bearing 23 and damage to the casing 2, making it impossible to continue operation. was required.

(Problems to be Solved by the Invention) As described above, in the conventional configuration, there is a problem that the function deteriorates due to a decrease in rotation speed.The present invention has been made based on the above points, and its purpose is to This eliminates the situation where cutting capacity is reduced or continuous operation becomes impossible due to various adverse effects caused by gel heat generation in the shaft, and it is highly reliable, such as being able to cut thick steel materials at high speed. Our goal is to provide a high quality arc saw cutting device.

[Structure of the Invention] (Means for Solving the Problems) That is, the arc saw cutting device according to the present invention includes a casing, and a bearing rotatably housed in the casing and having both ends pivotally supported by bearings installed in bearing chambers. In the arc saw cutting device, the shaft is provided with a rotating electrode fixed to the tip of the shaft, and a control mechanism for sliding the casing. The shaft is characterized in that the shaft is cooled by circulating the lubricating oil in one bearing chamber toward the other bearing chamber through the flow path.

(Function) In other words, a flow path is formed in the shaft so that the bearing chambers located at both ends communicate with each other, and the lubricating oil in one bearing chamber is moved to the other bearing chamber through the flow path. The idea is to lubricate and cool the shaft at the same time.

(Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a cross-sectional view of the head portion of the arc saw cutting device according to the present embodiment, and FIG.
IF sectional view, FIG. 3 is a sectional view taken along line I-1 in FIG. Note that the same parts as in the prior art are denoted by the same reference numerals, and the explanation thereof will be omitted. A plurality of channels 1 are provided in the shaft 3 in parallel to the axial direction.
As shown in FIGS. 2 and 3, the holes are formed at equal intervals in the circumferential direction. These channels 101 communicate with the bearing chambers 24°24. That is, the lubricating oil supplied into one of the bearing chambers 24 through the oil supply port 27 is
From there, it flows through the flow path 101 to the other bearing chamber 24 . This configuration is designed to cool the shaft 3 while flowing through the flow path 101, thereby suppressing the generation of Joule heat in the shaft 3.

The operation will be explained based on the above configuration. The rotating electrode 1 rotates due to the rotation of the shaft 3, and approaches the workpiece 9 as the casing 2 moves. When the object 9 approaches to a predetermined distance, arc discharge is performed to cut the object 9 and remove melting slag. During such a cutting operation, lubricating oil flows through the following path. That is, the lubricating oil supplied into one of the bearing chambers 24 through the oil supply port 27 lubricates the bearing 23 within the bearing chamber 24, and then
It flows into the flow path 101 of the shaft 3 that communicates with the bearing chamber 24 . The lubricating oil that has flowed into the flow path 10 flows into the other bearing chamber 24 via the flow path 101. Said flow path 101
The shaft 3 is cooled while flowing inside, thereby suppressing the accumulation of Zeal heat.

The lubricating oil that has flowed into the other bearing chamber 24 lubricates the bearing 23 within the bearing chamber 24 and is drained through the oil drain port 28 . After that, it is cooled and pressurized using an oil supply device (not shown).
It is led to the fuel filler port 27 again. Furthermore, it flows into one of the bearing chambers 24 again, and thereafter circulates in the same cycle.

As described above, according to the arc saw cutting device of this embodiment, the shaft 3 is formed with a flow path 10 that communicates the bearing chambers 24 and 24 on both sides, and the lubricating oil in one of the bearing chambers 24 is supplied through the flow path 101 between the two bearing chambers 24 and 24. The other bearing chamber 24 and shaft 3 can be cooled at the same time.

This can suppress the accumulation of Joule heat in the shaft 3, the expansion of the shaft 3, and the temperature rise of the bearing 23.23. At the same time, it is possible to suppress the burning of the bearing 23.23, a decrease in rotational speed, and the occurrence of cracks in the casing 2. It becomes possible to solve the problem. Therefore, reliability as an arc saw cutting device can be greatly improved, and even thick steel materials can be cut at high speed.

In the case of this embodiment, an arc saw cutting device that exhibits the desired effects can be obtained by a simple operation of forming a flow path rox in the shaft 3 of an existing device.

Next, a second embodiment will be explained. That is, in the case of the first embodiment, the lubricating oil was forcibly circulated by an oil supply device (not shown), but in contrast to this, the second embodiment
In this embodiment, the lubricating oil is circulated through natural circulation.

This will be explained below. Channel 101 formed in shaft 3
is formed in a so-called skinny state.

Therefore, each flow path 101 is formed in a direction inclined with respect to the axis of the shaft 3. By making it skinny in this way, a speed component force is generated in the axial direction as a component force of the rotational peripheral speed, and the lubricating oil is naturally circulated by the speed component force in the axial direction. Then, a cooling fan is installed on the outer surface of the oil reservoir provided outside the casing 2,
The lubricating oil that flows into the oil reservoir in a heated state is cooled by the water in the water.

According to the above configuration, not only can the same effects as in the first embodiment be achieved, but also there is no need for a mechanism for forcibly circulating the lubricating oil, and the device can be simplified and costs can be reduced. becomes possible.

In addition, the lubricating oil that flows through the flow path 101 of the shaft 3 and has increased in temperature can be effectively cooled, which is extremely effective in improving cooling efficiency.

[Effects of the Invention] As detailed above, the arc saw cutting device according to the present invention includes a casing, a shaft rotatably housed in the casing, and having both ends pivotally supported by bearings installed in a bearing chamber. In an arc saw cutting device including a rotating electrode fixed to the tip of the shaft and a control mechanism for sliding the casing, a flow path communicating with the bearings at both ends is formed in the shaft, and the flow path The shaft is characterized in that the shaft is cooled by circulating the lubricating oil in one bearing chamber toward the other bearing chamber through the bearing chamber.

Therefore, it is possible to suppress the generation of Joule heat and heat accumulation in the shaft, eliminate various adverse effects caused by Joule heat generation and heat accumulation, and prevent situations such as a decrease in cutting ability and the inability to operate continuously, resulting in high reliability. It becomes possible to provide an arc saw cutting device.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing one embodiment of the present invention.
The figure is a cross-sectional view of the head of the arc saw cutting device, Figure 2 is a cross-sectional view taken along line ■-■ in Figure 1, Figure 3 is a cross-sectional view 11 in Figure 1,
4 to 6 are diagrams showing a conventional example, in which FIG. 4 is a diagram showing a schematic configuration of an arc saw cutting device, FIG. 5 is a plan view of a rotating electrode, and FIG. 6 is a sectional view of a head portion. l...Rotating electrode, 2...Casing, 3...Shaft, 9...Object to be cut, 10...Cylinder mechanism, 2
3...Bearing, 24...Bearing chamber, 101...Flow path. Figure 4 Figure 5

Claims (3)

[Claims] (1) A casing, a shaft that is rotatably housed in the casing and whose both ends are supported by bearings installed in a bearing chamber, a rotating electrode fixed to the tip of the shaft, and the casing are slid together. In an arc saw cutting device equipped with a control mechanism, a flow path communicating with bearing chambers at both ends is formed in the shaft, and lubricating oil in one bearing chamber is distributed to the other bearing chamber through the flow path. An arc saw cutting device characterized in that the shaft is cooled by cooling the shaft. (2) The arc saw cutting device according to claim 1, wherein the flow passages are formed parallel to the axis of the shaft at equal intervals in the circumferential direction. (3) The arc saw cutting device according to claim 1, wherein the flow path is formed in an inclined state with respect to the axis of the shaft.