JP2670707B2 - Active gas plasma arc processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to improvement of an active gas plasma arc processing apparatus by a protective air flow method, and it is possible to reduce a small amount of inert protective gas before reaching a constriction of a torch. It is an object of the present invention to provide an active gas plasma arc machining device capable of improving the machining quality and the machining speed while sufficiently protecting the cathode rod of the torch by discharging the gas from the inside of the torch and ensuring the air flow condition of the path. The main purpose is.

[Problems to be solved by conventional technology and invention]

Generally, in a plasma arc cutting device in which a non-consumable electrode such as tungsten is used as a cathode rod and an active gas such as oxygen is supplied as a plasma gas, when the cathode rod is contacted with the active gas, it is oxidized and consumed in an instant. Therefore, a torch structure as shown in Fig. 4 has already been proposed in Japanese Examined Patent Publication No. 56-22428. In the figure, an inner nozzle 2, an intermediate nozzle 4 and an outer nozzle 3 which are concentrically arranged around the cathode rod 1 are provided, and the plasma arc is constricted by the constriction opening of the outer nozzle 3. Make up an arc torch. The first gas passage P1 for the protective gas formed between the cathode rod 1 and the inner nozzle 2 and the second gas for the active plasma gas formed between the intermediate nozzle 4 and the outer nozzle 3 The passage P2 is formed between the inner nozzle 2 and the intermediate nozzle 4, and is formed in the arc torch by the openings of the inner nozzle 2 and the intermediate nozzle 4, respectively.
Gas passages P1 and P2 of the outer nozzle 3 are connected to the gas passages P1 and P2, and the flow rate of the exhaust gas from the outside is adjusted. It has an opening sized to limit the flow of gas into the gas discharge passage. In the active gas plasma arc torch configured in this way, high temperature gas flows into the passage P3 from the inside of the torch, which may cause leakage or misalignment in the exhaust gas passage, and the cathode rod 1 and other configurations of the torch. Risk of burning parts. In particular, the torch moves for cutting work, but in order to maintain its mobility, the gas supply passage and the discharge passage are made of flexible material, and this danger exists.

[Means for solving the problem]

In order to solve the above problems, the present invention provides a pressure detecting means in the protective gas discharge passage, and monitors the gas pressure in this passage from the completion of pilot arc generation to the generation of a cutting arc to make it below a specified value. Then, the cutting arc is stopped.

〔Example〕

FIG. 1 shows an embodiment of the arc torch of the present invention. In the figure, 1 is a cathode rod, 2 is an inner nozzle, 3 is an outer nozzle, 4 is an intermediate nozzle provided between the inner nozzle 2 and the outer nozzle 3, and the inner nozzle 2 and the intermediate nozzle 4 are A gas discharge passage P3 is formed by. The intermediate nozzle 4 has an opening wider than the constriction of the outer nozzle 3 and having a size large enough to restrict the plasma gas GA in the second gas passage P2 from flowing into the gas discharge passage P3. The gas discharge passage P3 is for discharging the protective gas GN flowing out of the mouth of the inner nozzle 2 through the first gas passage P1 to the outside of the torch T. Reference numeral 7 is the polarity shown in the drawing, and the cathode rod 1
, A DC power source connected between the workpiece and the workpiece 5, 8,8 'and 9,9' are needle valves for adjusting the flow rate provided in the protective gas supply pipe, solenoid valves, and 10 is an inert gas (argon) Cylinder, 11
And 12 are needle valves and solenoid valves provided in the middle of the plasma gas supply pipe, 13 are active gas (oxygen) cylinders, 14
Numerals 15 and 15 are needle valves and solenoid valves which are provided in the middle of the gas discharge pipe communicating with the gas discharge passage P3 of the torch T and are used as control valves.

Next, the method of operating the torch T will be explained. First, FIG. 1 shows the time when a pilot arc is generated, and the changeover switch 17 is such that the positive pole of the DC power source is connected to the outer nozzle. Then, argon gas from the argon gas cylinder 10 flows into the gas passage GN through the solenoid valve 9'needle valve 8 ', an arc is generated in the cathode rod 1 and the outer nozzle 3, and the needle valve 14, solenoid valve passes through the gas passage GE. The generation of the pilot arc 6'is completed with a part of the gas being discharged to 15. Next, as shown in FIG. 2, argon gas is made to flow from the argon gas cylinder 10 to the passages of the solenoid valve 9 and the needle valve 8 and the solenoid valve 9'is closed. Then, through the needle valve 11, flow into the passage of the plasma gas GA. At the same time when oxygen flows into the narrowed portion of the nozzle 3, the switch 17 is switched to the workpiece 5 side,
A cutting arc 6 is generated.

In the torch T configured as described above, since the protective gas discharge path GE has the pressure detector 16, it is possible to check the adjustment failure of the pressure control valve 14 of the protective gas discharge path GE and the gas leak in the exhaust gas passage GE. it can. Therefore, as shown in FIG. 3, if the pressure of the protective gas GN inside the torch T is reduced or if the protective gas GN is defective, the DC power supply 7 is turned on by the signal from the pressure detector 16. Since the arc is stopped to stop the arc or an alarm is generated, the cathode rod 1 can be prevented from burning. Further, it can be confirmed that the internal pressure is insufficient at the completion of pilot arc generation due to a poor adjustment of the pressure adjusting needle valve 8'in the protective gas supply path.

〔The invention's effect〕

The present invention has the characteristics as described above, and when the protective gas pressure inside the torch is reduced or if there is a defect in the protective gas, the plasma arc is stopped by the signal from the pressure detecting means. Or an alarm is generated, it is possible to prevent the cathode rod from burning. Therefore, the safety and reliability of the torch itself can be improved and the reliability of plasma cutting work can be improved.

[Brief description of the drawings]

1 to 3 are views for explaining a torch structure and a method of operating the torch according to the present invention. FIG. 4 shows the structure of a conventional torch. T ... Torch, 1 ... Cathode rod, 2 ... Inner nozzle, 3 ... Outer nozzle, 4
… Intermediate nozzle, 5… Workpiece, 6 ′… Pilot arc, 6
… Cutting arc, 7… DC power supply, 8, 8 ′… Needle valve, 9, 9 ′…
Solenoid valve, 10 ... Argon cylinder, 11, 14 ... Needle valve, 12, 15
… Solenoid valve, 13… Oxygen cylinder, 16… Pressure detector, 17… Changeover switch, P1… First gas passage, P2… Second gas passage, P3
… Gas exhaust passage, GE… Exhaust gas, GN… Protective gas (inert gas), GA… Plasma gas (active gas)

Claims (1)

(57) [Claims] 1. A processing apparatus provided with an arc torch having a first gas passage for a protective gas and a second gas passage for a plasma gas which are concentrically arranged around a cathode rod,
A gas discharge passage and a gas discharge passage for discharging the protective gas formed between the first gas passage and the second gas passage and flowing out of the first gas passage to the outside of the torch. An active gas plasma arc machining apparatus, comprising: a pressure detection means connected in series, wherein the arc is stopped and / or an alarm is issued when the detection value of the pressure detection means is below a set value. .