JPH01148462A - Arc saw cutting device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an accident of an arc saw due to overheat of a shaft by providing plural channels to the shaft for a rotating electrode on an arc sawing device for underwater cutting and passing compressed air from a brush chamber for feeding to the shaft through plural 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 electrode current is generated between the electrode 1 and material to be cut to cut the material to be cut. In this case, the high electric current is also carried to the shaft 3 which is made to the high temperature by Joule heat and accidents such as burning of bearings 23 and the occurrence of a crack on a casing 2 for the shaft take place and cutting capacity of the arc sawing device declines. Many channels 102 are provided to the shaft 3 on this device and the compressed air is pressed in the brush chamber 25 wherein copper brushes 5 to feed to the shaft 3 are put from an inlet 16 and carried to an air release chamber 101 through the channels 102 and released from an air release port 103. The shaft 3 is cooled by this air flow and prevented from being overheated by the Joule heat.

Description

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

(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 is 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. Additionally, 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. Therefore, 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. As shown in FIG. 5, slits JA are formed at equal intervals in the circumferential direction on the outer peripheral edge of the rotating electrode 1, and the molten material (molten slag) is scraped out by the slits IA. This shaft 3 is connected to a hydraulic motor 4 installed outside the casing 2, and by driving this 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 10.
As the piston 11 slides, the casing 2 slides toward and away from the object 9 to be cut. The hydraulic cylinder mechanism 10 is controlled by a serging system 12. That is, when cutting is performed by bringing the rotating electrode 1 close to the object 9 to be cut, the cutting current is detected by the ammeter 13 inserted in the cable 6,
The detection signal is input to the current comparator 14. In addition to the detection signal described above, a control signal set in advance from the control panel 15 is input to the current comparator 14.

The current comparator 14 compares these detection signals and control signals and outputs the difference therebetween to the servo system 12 as a difference signal. The servo system 12 controls the hydraulic cylinder mechanism 10 based on this difference signal to maintain the cutting current constant. Note that reference numeral 16 in the figure indicates an air inlet, and compressed air as a shielding gas is injected into the casing 2 through this air inlet 16 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 then 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 mmIJ away, and a DC low voltage high current (voltage approximately 5 mm) is generated.
The cutting work is performed by melting the object 9 with electrical energy of 0 V and current of 4000 A to 20000 A, 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 portion, and the rotating electrode 1 is fixed to the shaft 3 with a screw 21. Both ends of the shaft 3 are supported by roller bearings 23 and 23 through an insulator 22, respectively.

These roller bearings 23.23 are installed in a bearing chamber 24.24 formed in the casing 2, and the portion where the brush 5 is installed serves as 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 16 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 core heat is stored without being cooled, resulting in an abnormally high temperature. 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. Improvement was required.

(Problems to be Solved by the Invention) As described above, the conventional configuration has the problem that the function deteriorates due to a decrease in rotational speed, etc., and the present invention has been made based on the above points. The purpose is to eliminate situations where cutting capacity is reduced or continuous operation becomes impossible due to various adverse effects caused by the generation of heat from the shaft, and to provide reliability such as being able to cut thick steel materials at high speed. The purpose of the present invention is to provide an arc saw cutting device with high performance.

[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. an arc saw cutting device comprising: a shaft; a power supply brush installed on the outer periphery of the shaft within the casing; a rotating electrode fixed to the tip of the shaft; and a control mechanism for sliding the casing. , the part where the brushes are installed is used as a brush chamber, an exhaust chamber is formed adjacent to the bearing chamber on the rotating electrode side, and a flow path is formed in the shaft so as to communicate these brush chambers and the exhaust chamber. However, the shaft 7 is cooled by flowing the shielding gas supplied to the brush chamber to the exhaust chamber through a flow path.

The brush chamber and the exhaust chamber installed adjacent to the bearing chamber on the rotating electrode side are communicated through a flow path formed in the shaft, and the shielding gas supplied to the brush chamber is passed through the brush chamber, the flow path, and the exhaust chamber. The idea is to cool the shaft by letting sweat pass through the tied route.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a sectional view of the head portion of the arc saw cutting device, FIG. 2 is a sectional view taken along the line 1--n in FIG. 1, and FIG. 3 is a sectional view taken along the line mm in FIG. Note that parts that are the same as those in the prior art are designated by the same reference numerals, and a description thereof will be omitted. An exhaust chamber 101 is installed adjacent to the bearing chamber 24 on the rotating electrode 1 side. A plurality of channels 102 are formed in the shaft 3 so as to communicate the exhaust chamber 101 and the brush chamber 25.

The flow paths 102 are arranged parallel to the axis of the shaft 3, and are formed at equal intervals in the circumferential direction as shown in FIGS. 2 and 3.

Note that the exhaust chamber 101 is sealed by a seal member 26. That is, an exhaust chamber 101 is installed adjacent to the bearing chamber 24 on the rotating electrode 1 side, and a flow path 102 is formed in the shaft 3 so as to communicate the exhaust chamber 101 and the brush chamber 25, thereby supplying the brush chamber zsK. The shaft 3 is cooled by circulating compressed air through a route connecting the brush chamber 25, the flow path 102, and the exhaust chamber 101.

Note that the reference numeral 103 in the figure indicates an exhaust port formed in the exhaust chamber 101.

The operation will be explained based on the above configuration. First, rotating electrode 1
is rotated by the rotation of shaft 3, and at the same time casing 2
The object to be cut 9 is approached by the movement of the object. When the object 9 approaches a predetermined distance, arc discharge is performed to cut the object 9 and remove melting slag by the slit IA.

During this cutting operation, compressed air supplied from a compressed air supply device (not shown) into the brush chamber 25 through the inlet 16 flows through the following path.

Compressed air supplied into the brush chamber 25 through the inlet 16 flows into a flow path 102 formed in the shaft 3 and flows toward the exhaust chamber 101 . At that time, the shaft 3 is cooled, and generation of Joule heat and heat accumulation in the shaft 3 are effectively suppressed. The compressed air that has flowed into the exhaust chamber 101 is exhausted through the exhaust port 103. Compressed air flows through the same route below.

As described above, according to the arc saw cutting device according to the present embodiment, the compressed air forming the shield of the power supply part is passed through the flow path 102 formed in the shaft 3 toward the exhaust chamber 101, so that the shield of the power supply part is Of course, by cooling the shaft 3, it is possible to effectively suppress the generation of Joule heat and heat accumulation. As a result, the shaft 3 expands,
It becomes possible to suppress the rise in temperature of the bearing 23 and solve problems such as seizure of the bearing 23, decrease in rotational speed, and occurrence of cracks in the casing 2. Moreover, a highly reliable arc saw cutting device capable of cutting even thick steel materials at high speed can be obtained.

[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. An arc saw cutting device comprising: a power feeding brush installed in the casing and on the outer periphery of the shaft; a rotating electrode fixed to the tip of the shaft; and a control mechanism for sliding the casing.
The part where the brushes are installed is used as a brush chamber, and an exhaust chamber is formed adjacent to the bearing chamber on the rotating electrode side.
A flow path is formed in the shaft so as to communicate the brush chamber and the exhaust chamber, and the shield gas supplied to the brush chamber is passed through the flow path to the exhaust chamber to cool the shaft. That is.

Hence the generation of Joule heat in the shaft.

It is possible to suppress heat accumulation, eliminate the generation of Joule heat and various adverse effects caused by heat accumulation, and prevent situations such as a decrease in cutting capacity and the inability to perform continuous operation, thereby providing a highly reliable 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 an arc saw cutting device, Figure 2 is a cross-sectional view taken along ■-■ in Figure 1, Figure 3 is a cross-sectional view taken along ■-■ in Figure 1, and Figures 4 to 6 are conventional examples. 4 is a diagram showing a schematic configuration of the arc saw cutting device, FIG. 5 is a plan view of the rotating electrode, and FIG. 6 is a sectional view of the head portion of the arc saw cutting device. N...Rotating electrode, 2...Casing, 3...Shaft, 9...Object to be cut, 1o...Cylinder mechanism, 2
3... Bearing, 24... Bearing chamber, 25... Brush chamber, 1o... Exhaust chamber, 102... Channel, 103...
exhaust port. Applicant's agent Patent attorney Takehiko Suzue 7th 4th
Figure 5

Claims (2)

[Claims] (1) A casing, a shaft rotatably housed in the casing and supported at both ends by bearings installed in a bearing chamber, and a power supply brush installed inside the casing and on the outer periphery of the shaft. In an arc saw cutting device comprising a rotating electrode fixed to the tip of the shaft and a control mechanism for sliding the casing, the part where the brush is installed is a brush chamber, and a bearing on the rotating electrode side is used. An exhaust chamber is formed adjacent to the chamber, a flow path is formed in the shaft so as to communicate the brush chamber and the exhaust chamber, and the shielding gas supplied to the brush chamber is distributed to the exhaust 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 arranged parallel to the axis of the shaft and formed at equal intervals in the circumferential direction.