JP2510061Y2 - Plasma arc processing equipment - Google Patents

Description

[Detailed description of the device]

[0001]

INVENTION The present invention relates to a welding by a plasma arc cutting, relates plasma arc processing apparatus for performing thermal spraying, when igniting the pilot arc between the tip electrode and the main electrode the high-frequency voltage is applied with the path for the pilot arc voltage sparking discharge between superimposed both electrodes thereto, thereby to an improvement of the apparatus so as to induce a pilot arc.

[0002]

2. Description of the Related Art In a plasma arc machining apparatus of the type in which a plasma arc is generated between a work piece and a main electrode with the aid of a pilot arc for machining, generally, a partial sectional view and a connection diagram are shown in FIG. It is configured as shown in. In the figure, 1 is working torch a and main electrode 12 is sandwiched by the chuck 11 inside, the main electrode 12 at a position surrounding the attached nozzle-shaped insulated tip electrode 13, protective cover-up 14 and it encompasses the start-up finger Ryosu switch 15. Although not shown, the plasma generating working gas is supplied between the main electrode 12 and the tip electrode 13 and is ejected to the outside from the orifice portion provided at the tip of the tip electrode 13. Reference numeral 2 is a processing power supply device, which converts an AC power supply into a DC output having characteristics suitable for plasma processing.
/ DC converting unit and start and stop, the control <br/> to that control circuit 21 and supply of the working gas, the switch 22, the current limiting element 23, the high-frequency generator 24, outputs a chip electrode of the high frequency generating means 24 Coupling coil 25 for superimposing on the pilot circuit up to 13, high-frequency bypass capacitor 26a
To 26c and choke coil 27 for high frequency blocking
It is composed of a and 27b. In addition, 3 is a workpiece.

[0003] system positive output of the control circuit 21 is connected switch 22 is connected directly to the workpiece 3 through a current-limiting element 23 and the coupling coil 25 to the tip electrode 13. Negative output of or control circuit 21 is connected to the main electrode 12 directly torch 1. In addition electromotive torch 1
The motion command switch 15 is connected to the start command input terminal of the processing power supply device 2. In order to improve the workability, each of these connection cables is integrated with the working gas supply hose (not shown) except for the power cable (ground cable) that connects the workpiece 3 and the positive output terminal. Usually several meters to 10 when bundled and in close contact with each other
It is manufactured as a composite cable with a length of several meters.

In the conventional apparatus shown in FIG . 2 , the torch 1 is raised.
Dynamic instruction switch 15 braking the <br/> together with the working gas is supplied is pressed control circuit 21 outputs a predetermined output voltage between the positive and negative terminals, also the high-frequency generator 24 is high-frequency electric Generate pressure. The control positive output of the control circuit 21 in the switch 22 is closed for the start command from the start command switch 15 reaches the switch 22, the current limiting element 23, tip electrode 13 of the torch 1 via a coupling coil 25.

The output voltage is coupled to the coupling coil 25.
Since the output a is Hangzhou wave voltage of the high frequency generating means 24 are superimposed, the insulating is destroyed by this spark discharge between the tip electrode 13 and main electrode 12 is generated by,
This spark discharge triggers an arc discharge (pilot arc).

The current of the pilot arc is limited to a relatively small value by the current limiting element 23. There are some high-frequency generators 24 that stop their output when the pilot arc is generated.
Since the pilot arc is likely to be blown out by the working gas flowing at high speed, it is usually configured to continuously operate until the main arc is generated and machining is started.

When the torch 1 is brought close to the work piece 3 in this state, when the ionized portion of the working gas comes into contact with the work piece 3 by the pilot arc, the main electrode 12 and the work piece 3 are mainly contacted with each other. An arc occurs. When the generation of this main arc is detected, the high frequency generating means 24 stops its output, and the switch 22 is opened, so that the pilot arc is extinguished.

The high-frequency voltage supplied for starting and maintaining the pilot arc causes an electronic circuit inside the machining power supply unit 2 to malfunction due to induction or cause an accident such as damage of parts due to overvoltage. , Capacitors 26a, 2 inside the coupling coil 25
6b is connected to bypass the high frequency voltage.

Further, the high frequency voltage induced in the control cable from the start command switch 15 is also affected by the choke coil 27a,
It is prevented from entering the machining power supply apparatus 2 a low-pass filter consisting of 27b and the capacitor 26c by insert.

[0010]

In the above-mentioned conventional device, the high frequency voltage can be prevented from entering the processing power supply device 2 , but the high frequency voltage cannot be prevented from leaking. That is,
Main electrode 12 and chip electrode 1 on which high-frequency voltage is superimposed
The distributed capacity is connected in parallel between the power supply cable to 3 and the control cable arranged in close contact,
Also distributed capacitance is present between the respective control cable and ground. The high frequency voltage is bypassed and attenuated by these distributed capacitances. Furthermore, the insulation resistance in the torch 1 is low, and the tip electrode 13 and the main electrode 12 will be
The insulation resistance between the control command switch 15 and the start command switch 15 also becomes low.

Further, an electrode for detection is provided between the cup 14 and the body of the torch 1 in order to detect that the protection cup 14 is securely attached to the tip electrode 13, and this is determined by the attachment of the cup. In a torch that detects that a short circuit has occurred and uses it as a work enable signal, it is very difficult because the green between the tip electrode 13 and the protective cup mounting detection electrode is a narrow place,
Insufficient insulation resistance cannot be obtained. For this purpose, the tip electrode 1
The high frequency voltage applied to 3 may leak from these insulating parts and flow into the control cable . In such a case, the high frequency voltage is transmitted to the terminals of the processing power supply device 2 through the long cable. Therefore, the high frequency voltage is applied to a plurality of long cables and is bypassed by the distributed capacitance between the cable and the ground. As a result, the high frequency voltage is greatly attenuated.

These attenuations become larger as the cable becomes longer, so that the voltage applied between the tip electrode 13 and the main electrode 12 in the torch 1 is reduced, weakening the spark discharge,
In extreme cases, the ignition of the pilot arc may be disabled. Furthermore, since a high frequency voltage of several MHz is induced in an unnecessary cable, this acts as an antenna, increasing the emission of radio waves into the air, which becomes a source of radio interference.

[0013]

According to the present invention, an output of a light emitting diode is connected to a processing torch side by connecting a protection electrode of a tip electrode for detecting a protective cup mounting, a power source and a contact of a start command switch in series to a light emitting diode. is obtained by solving the above problems of the conventional device by a structure in which a photoelectric conversion circuit for converting an electric signal input light to the control circuit and guides the light to the control circuit of the machining power supply apparatus by optical fiber bucket Buru .

[0014]

FIG. 1 shows an embodiment of the present invention. In the figure, the processing power supply device 2 includes a phototransistor 29 instead of the choke coils 27a and 27b and the capacitor 26c.
Is equipped with a processing torch 1 and a processing power supply device 2.
An optical fiber cable 4b is provided as a control cable connecting the phototransistor 29 of FIG.

Further, torch body protection torch body side coupling mounting detection electrode 17a is in the 1, detection electrode 17a when mounted on 17b is provided a cup 14 side, 17b
A ring-shaped short-circuit electrode 18 for short-circuiting is provided. Detection electrode 17a, 17b is the start command switch 1
5 contacts, power E, resistor R and a light emitting diode 28
It is connected in series with the start command switch 1 only when the cup 14 is completely attached to the torch body.
5 is effective. Also C1, C2
Are each a capacitor, high frequency voltage is a light emitting diode is applied between the tip electrode 13 and main electrode 12 2
Light emitting diode 2 when induced or mixed in circuit 8
8 is a bypass capacitor for protecting the power supply E and the power supply E from destruction. Also between the phototransistor 29 is used to start and stop command to the control circuit 21 of the power supply device 2 and the light emitting diode 28 of the machining torch 1 is connected at fiber optic bucket <br/> Buru 4b There is.

The optical fiber connector 31 output optical signals of the light emitting diode 28 which has passed through the optical fiber cable 4b
The phototransistor 29 is irradiated from b through the optical fiber cable 30b.

In the processing apparatus shown in FIG.
GaSo are wearing, the detection electrodes 17a, 17b presses the start command switch 15 in a state in which conducting light emitting diode 28 emits light, the output optical signal is an optical fiber
By a cable 4b is transmitted to the phototransistor 29 by conducting this activates the control circuit 21. Start
When the command switch 15 is released, the output light of the light emitting diode 28
Phototransistor 29 becomes a cut-off because the signal is not, control circuit 21 also stops operating.

[0018]

As described above, in the present invention, since the processing torch and the control circuit of the processing power supply device are connected by the optical fiber cable to exchange the control signal, the long cable Since the high frequency voltage does not leak to the control cable on the way or inside the processing torch, there is no attenuation of the high frequency and the ignition of the pilot arc does not fail. In addition, the control cable has high frequency
Controls even if a long cable is used because the voltage does not leak
High-frequency radiation from the cable is reduced and radio interference can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a conventional device.

[Explanation of symbols]

1 machining torch 2 machining power unit 4b optical fiber cable 12 main electrode 13 tip electrode 14 protective cup 15 starts finger Ryosu switch 17a, 17 b protective cup mounting detection electrode 18 short-circuit electrode 21 control circuit 24 high-frequency generator 25 coupling coil 28 shots photodiode 29 phototransistor E power

Claims (1)

(57) [Scope of utility model registration request] 1. A plasma arc machining apparatus in which a pilot arc is ignited between a main electrode and a tip electrode of a machining torch by superposing a high-frequency voltage on a pilot arc power supply circuit. The torch has a protection cup attached to a position surrounding the tip electrode, two or more protection cup attachment detection electrodes provided on the body side of the processing torch, and a protection cup provided on the protection cup and attached to the torch body. When the protection
The short-circuit electrode that short-circuits the mounting detection electrode and the protective cap
-Up mounting detection electrodes, the short-circuit electrode, the power source, light emitting diode and the start command includes a series circuit consisting of a contact of the switch, the light-emitting diode optical fiber cable output light to the control circuit of the machining power supply apparatus And a plasma arc processing apparatus having a photoelectric conversion circuit for converting the output light from the optical fiber cable into an electric signal in the control circuit.