JPH0614938Y2 - Water-cooled plasma arc processing equipment - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an improvement of a water-cooled plasma arc processing apparatus that performs processing such as welding and cutting of a workpiece while cooling a processing torch with cooling water. It is a thing.

<Prior Art> In a processing device that uses a large current or a processing device with a high allowable usage rate, the inside of the torch is water-cooled in order to prevent overheating of the processing torch. In the plasma arc processing torch, in particular, the temperature of the nozzle electrode portion and the main electrode portion rises remarkably, and in order to improve the cooling efficiency, a cooling water passage is formed inside these to directly cool the water.

Here, an example of a water-cooled plasma arc processing torch will be described with reference to FIG. FIG. 5 is a sectional view showing an electrode portion of a water-cooled torch. In FIG. 5, 51
Is a hollow electrode, 55 is an insulating sleeve provided outside the supporting portion of the electrode 51, 56 is a nozzle supporting member made of a conductive material provided outside the insulating sleeve 55, and 52 is supported at the tip of the nozzle supporting member 56. An orifice 54 for jetting a working gas is formed in the center of the tip of the hollow nozzle. 57 is an insulating cup, 58 is a guide pipe for cooling water,
The cooling water flowing in from the supply hose 59 directly cools the electrode 51 and then flows out of the torch through the drain hose 60 through the passage passing through the nozzle 52 as shown by the arrow. The working gas G for forming the plasma arc is supplied through a gas passage that is provided concentrically with the electrode 51 and is ejected from the orifice portion 54 of the nozzle 52.

When the plasma arc processing torch 5 is used, the cooling water supply source and the supply hose 59 are connected via an on-off valve, and the on-off valve is closed when replacement parts such as the electrode 51 and the nozzle 52 are replaced. The cooling water supply was shut off.

In this case, however, the torch is still full of cooling water, and when the parts are removed, this residual water overflows and wets the torch and the work piece, causing the risk of electric shock and the next contact. If the work piece is cut while it is wet, hydrogen will be mixed into the cut surface, which may lead to deterioration of the welding quality thereafter.
Furthermore, in winter, residual water may freeze at night and destroy the torch. For this reason, a system has been proposed in which a pressure gas for removing residual water in the torch is introduced into the cooling water passage by operating the changeover switch. (For example, JP-A-55-19431 and JP-A-59-1346.
No. 00) FIG. 6 shows an example of an apparatus of this system. 5 in the figure
Is a torch for plasma arc machining having a replacement part that is directly water cooled, for example, having the structure shown in FIG.
In this case, among the replacement parts, the electrode 51 and the nozzle 52
Is directly water cooled. The cooling water supply hose 59 and the drainage hose 60 of the torch 5 communicate with each other through the inside of the processing torch 5 to form a cooling water circulation path. 1
Reference numeral 02 is a water storage tank for storing cooling water, and 101 is a water supply pump. The discharge side of the water pump 101 is connected to a pipe 108 via a two-way solenoid valve 103. 104 is a pressure gas supply source, for example, an air compressor. The pipe 107 on the discharge side is connected to the pipe 108 via a two-way solenoid valve 105.

In the apparatus shown in the figure, during normal processing work, the discharge water of the water feed pump 101 reaches the pipe 108 and the compressed air output of the air compressor 104 is cut off between the pipe 107 and the pipe 108 so as not to reach the pipe 108. Solenoid valve 1
03 is opened and the solenoid valve 105 is closed. In this state, the water feed pump 101 is driven to forcibly cool each part of the processing torch 5. Next, when replacing the parts, the solenoid valve 103 is closed and the solenoid valve 105 is opened. Then, the cooling water passages 59, 6
Compressed air is pumped from 0, 108, and 109 from the air compressor 104 to forcibly remove residual water in each passage and the processing torch 5. After the residual water is removed from the cooling water passage, the replacement parts of the cutting torch 5 are removed, and repairs and replacements are performed.

<Problems to be solved by the invention> In the above-mentioned conventional device, a switching valve is provided to introduce pressure gas into the cooling water passage when parts of the processing torch are replaced or when work is completed, and this is operated by a manual command. Since the switching is performed, there is no point in providing a switching valve when the operator forgets to operate it, and it is not possible to prevent water leakage when parts are removed or freezing in winter.

Further, in the case where the changeover valve is an electromagnetic valve and is changed over by a changeover switch or another signal, the electromagnetic valve for removing the cooling water is operated even after the power supply to the processing power supply is cut off. Since it was necessary to turn on the power of the, there was a risk of causing an electric shock accident during the repair work.

<Means for Solving Problems> In order to solve the problems of the above-mentioned conventional device, the present invention always supplies power to the power supply device for safety when removing torch parts or finishing work. Focusing on shutting off the power supply, a circuit is provided to discharge the charge stored in the capacitor that is charged during the power supply period through the exciting coil of the solenoid valve for introducing pressure gas when the power is cut off, and the pressure gas is discharged for a fixed time when the power is cut off. It is configured to open the solenoid valve for introduction.

Further, in the present invention, a gas pressure detection switch is provided on the pressure gas source side, and a circuit for prohibiting the opening of the electromagnetic valve for gas introduction is provided when pressure gas does not exist, so that a problem occurs even when the pressure gas is lost. I did not try to do it.

<Operation> The apparatus of the present invention operates as described above so that the pressure gas is automatically introduced into the torch immediately after the power is cut off and the cooling water remaining in the cooling water pipe is forcibly discharged. Further, when the pressure gas does not exist, the above-mentioned gas introduction operation is prohibited to prevent the cooling water from leaking to the gas pipe.

<Embodiment> FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 is an AC power supply, and three-phase or single-phase AC is used. Reference numeral 2 is a power switch, and 3 is a rectifying circuit, which converts the electric power of the AC power supply 1 into DC. C1 is a capacitor, which can be substituted when the output terminal of the rectifier circuit 3 includes a smoothing capacitor having an appropriate capacity. Reference numeral 4 denotes a cutting power adjusting circuit, which is a known power adjusting circuit for plasma arc processing, which receives the output of the rectifier circuit 3 as an input, adjusts it with a switching element, and converts it into electric power having a voltage / current characteristic necessary for plasma arc processing For example, it is a circuit in which a transistor type series regulator or an inverter is combined with a transformer and a rectifying circuit. Reference numeral 5 is a cutting torch, and the main electrode 51 and the nozzle 52 have a cooling water passage.
6 is a workpiece, 7 is a starter attached to the cutting torch 5.
It is a stop command switch and is usually called a torch switch. Reference numeral 8 denotes a control circuit, which supplies a control signal of output current and voltage to the power adjustment circuit 4 in response to a command from the torch switch 7 and also an exciting coil of a solenoid valve for supplying / stopping the gas for plasma generation to / from the torch 5. 115c is controlled. Reference numeral 101 is a pump for supplying cooling water, 102 is a water storage tank, 103 is a two-way solenoid valve for supplying and stopping cooling water, and is connected to the water supply pump by a pipe 106, and is connected to a cooling water inlet of the torch 5 by a pipe. They are connected at 108. 1
Reference numeral 04 is a pressure gas source, and a compressed air source or a plasma working gas source can be used. Reference numeral 105 denotes a two-way solenoid valve for introducing pressure gas, which is connected to the pressure gas source 104 by a pipe 107, and is also connected to a cooling water pipe 108 via a branch pipe 108a. As the exciting coil 105c of the solenoid valve 105, a DC solenoid valve that operates with a DC voltage is used. These solenoid valves 103 and 105 operate reciprocally so that when one of them is opened, the other is closed. Normally, when the power is turned on, the solenoid valve 103 is opened and the solenoid valve 105 is closed. There is. CR1 is a relay, which acts as a voltage responsive switch which is excited when the power switch is closed and electric power is supplied from the AC power source to close the normally open contact CR1a and open the normally closed contact CR1b. MS1 is an electromagnetic contactor, which is excited by the application of an AC power source and is relayed by the normally open contacts MS1a like the relay CR1.
To drive. R1 is an exciting coil 105c of the solenoid valve 104
It is desirable to use a resistor connected in parallel with the resistor whose resistance value can be adjusted. Here, the capacitor C1, the relay contact CR1b, and the coil 105c (and the resistor R1) form a timed operation open circuit of the solenoid valve 105. The first
In the figure, other output regulators, a plasma working gas supply circuit, and the like are omitted because they are not relevant to the gist of the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment shown in FIG. 1, where (a) is the open / closed state of the power switch, (b) is the change in the terminal voltage of the capacitor C1, (C). Is the operation of the torch switch, (d) is the operating state of the normally closed contact CR1b of the relay CR1, (e) is the operating state of the solenoid valve 105, (f) is the cooling water pipe 1
Changes in the state within 08 are shown over time.

In the embodiment shown in FIG. 1, when the power switch 2 is closed, the output of the AC power supply 1 is supplied to the rectifier circuit 3 and converted into a DC voltage. This DC voltage causes the capacitor C1
Is charged and its terminal voltage rises rapidly. On the other hand, when the switch 2 is closed, the output of the AC power supply 1 is relay CR1.
And the normally open contacts CR1a, which are also supplied to the electromagnetic contactor MS.
MS1a and MS1a are closed, and the common contact CR1b is opened at the same time. This drives the water pump 101, and the solenoid valve 103
When the is opened, cooling water is supplied to the torch 5. At this time, the solenoid valve 105 remains closed because the coil 105c is in the non-excited state because the contact CR1b is released. On the other hand, the control circuit 8 is closed by closing the power switch 2.
Is also supplied with power. When the torch switch 7 is closed in this state, the electromagnetic valve 115 for supplying the plasma working gas is excited thereby to supply the gas to the torch 5. After a predetermined time, the output command signal is supplied to the power adjusting circuit 4 and the processing power is supplied to the torch 5, and the torch 5 is started by a known plasma arc starting procedure.

Next, when the torch switch 7 is opened, the power adjustment circuit 4 stops the supply of power to the torch 5, and after a predetermined time, the electromagnetic valve 115 is deenergized and closed to stop the supply of the plasma working gas, and the power is supplied once. Finish the processing work. After that, processing is performed according to ON-OFF of the torch switch 7.

When the power switch 2 is released at the end of the work or the repair of the torch after the completion of the series of processing, the relay CR1 and the electromagnetic contactor MS are de-energized, which stops the water pump 101 and also closes the electromagnetic valve 103. Further, since the normally closed contact CR1b of the relay CR1 also returns, the relay contact CR1b and the solenoid valve 105 are connected to the capacitor C1.
The series circuit with the exciting coil 105c is connected in parallel. As a result, immediately after the power switch is opened, the charge stored in the capacitor C1 is discharged through the exciting coil 105c and the resistor R1.
Open 05. As a result, the cooling water pipe 108 is connected to the pressure gas source 104, and the cooling water remaining in the pipe 108 and the torch 5 is forcibly discharged to the tank 102 by the supplied pressure gas.

The terminal voltage Vc1 of the capacitor C1 gradually decreases as it discharges through the coil 105c and the resistor R1.
When the terminal voltage Vc1 of the capacitor C1 drops below the return voltage Vs of the solenoid valve 105, the solenoid valve 105 is closed and the supply of pressurized gas is stopped.

The time Ta from the opening of the power switch 2 to the return / close of the solenoid valve 105 is determined by the capacity and charging voltage of the capacitor C1, the return voltage V2 of the solenoid valve 105 and the resistance value of the exciting coil. Of these, the charging voltage is determined by the output voltage of the rectifier circuit 3, and the capacity of the capacitor C1 is also determined as the capacity required for smoothing the output of the rectifier circuit 3.
Therefore, there is little room for adjusting the time Ta. Normally, the capacitor C1 having a large capacity of several hundreds to several thousand microfarads is used, and the reset voltage of the DC solenoid valve 105 is considerably lower than the rated voltage, so that the time Ta is expected to be considerably long. Therefore, in the embodiment shown in FIG. 1, a resistor R1 is connected in parallel with the exciting coil 105c in order to adjust this time to a degree slightly longer than the time required for draining the cooling water in the pipe. . By setting the resistance value of the resistor R1 to an appropriate value, the required length of time is obtained. Excitation coil 1
It is not necessary to provide this resistor R1 when only 05c provides an adequate time.

When the smoothing capacitor is provided in the rectifier circuit 3 or when the capacity of the smoothing capacitor is too small, the rectifier circuit 3 is used only for exciting the solenoid valve 105.
It is uneconomical to add a capacitor to the output side of this circuit because it is necessary to prepare a high voltage electrolytic capacitor because the voltage of this circuit is high, and a large capacity capacitor is added. It is conceivable that an inrush current will flow through the circuit and adversely affect other circuits.

FIG. 3 is a connection diagram showing another embodiment of the present invention suitable for such a case. In the figure, instead of the capacitor charged by the output of the rectifier circuit 3, a capacitor C2 charged from an AC power source through a diode D1 is provided. A series circuit of the exciting coil 105c of the solenoid valve 105 for introducing pressure gas and the normally-closed contact CR1b of the relay CR1 that operates as a voltage responsive switch that closes when the AC power is cut off is connected in parallel to the capacitor C2 to connect the solenoid valve 105. A timed operation circuit is configured. Since other parts are the same as those of the embodiment shown in FIG. 1, those having the same functions are designated by the same reference numerals and detailed description thereof will be omitted.

In the embodiment shown in FIG. 3, the opening time of the solenoid valve 105 for forcibly removing the cooling water is determined by the charge of the capacitor C2 and the resistance value of the exciting coil 105c of the solenoid valve 105. Can be set to. As a result, the degree of freedom in design for accurately matching the opening time of the solenoid valve 105 with the time required for discharging the cooling water is increased without being influenced by the capacity of the smoothing capacitor of the rectifier circuit 3.

In the embodiment shown in FIG. 1 and FIG. 3, it is inexpensive to use compressed air as the pressure gas source for removing the cooling water, but when compressed air is not available at hand, it is for plasma operation. Gas can be used.

In this case, the gas source for operating the plasma is simply replaced by the pressure gas source 1
There is a slight problem when the flow is divided into the cooling water pipe 108 via the solenoid valve as 04.

Since the plasma gas source is naturally connected to the gas passage of the plasma torch, if the pressure of the gas source drops or is zero, the cooling water is supplied to the plasma working gas when the cooling water removing solenoid valve is opened. May flow back to the piping side. If the cooling water flows back to the plasma working gas pipe side, this water will be mixed into the gas passage of the torch at the next plasma arc startup, not only causing a leakage accident but also generating the plasma arc itself. Even if somehow the plasma arc is generated, the working gas will contain a large amount of water vapor, and a large amount of hydrogen will be mixed into the work piece, and the quality of the cut part will be extremely reduced. become.

FIG. 4 is a connection diagram showing another embodiment of the present invention which solves the above problems, and uses a plasma arc operating gas source as a pressure gas source. In the figure, reference numeral 116 is a gas source for operating a plasma arc, and an inert gas such as argon gas or compressed air is used. The gas source 116 is supplied through the solenoid valve 115 between the electrode 51 of the torch 5 and the nozzle 52 at the time of processing to generate a high-temperature plasma flow due to the arc, which is ejected from the opening at the tip of the nozzle 52, whereby the workpiece 6 Is melt processed. Gas source 116
Is also connected to the branch pipe of the cooling water pipe 108 through the solenoid valve 105. Each solenoid valve 105 from the gas source 116
A pressure switch 114 for detecting the pressure of the gas source is provided in the middle of the pipe 107 to and 115. The normally open contact 114a of the pressure switch 114 is a relay contact CR.
It is connected to the exciting coil 105c of the solenoid valve 105 in series with 1a.

In the embodiment of FIG. 4, when the pressure gas source 116 does not have a pressure higher than a predetermined value, the solenoid valve 105 does not open because the contact 114a of the pressure switch 114 remains open even if the power switch 2 is opened, and therefore the cooling is performed. Water does not flow back into the gas pipe 107. Then, if the alarm device 117 such as a buzzer or a lamp is operated by the normally closed contact 114b of the pressure switch 114, it is possible to notify the operator of a shortage of working gas and incomplete drainage in the torch.

In each of the above-described embodiments, an example has been shown in which the cooling water is sucked up and supplied from the water storage tank by a dedicated circulation pump, but it goes without saying that the cooling water may be supplied from water supply, industrial water, or the like. Further, as the power supply circuit for generating the plasma arc, any type of power supply circuit can be used other than the combination of the illustrated rectifying circuit and the output adjusting circuit using the switching element. In this case, when the power supply circuit includes a capacitor which is always charged when the power switch is turned on and has an appropriate capacity, this capacitor is used as the capacitor C1 for exciting the coil of the solenoid valve for introducing pressure gas according to the present invention. Good. When such a capacitor is not included, a capacitor circuit for exciting the solenoid valve may be separately provided as shown in FIGS. 3 and 4.

<Effect of device> Since the device of the present invention is as described above, the cooling water in the torch is forcibly removed without fail by the operator releasing the power switch at the end of work or repair. There is no accident due to forgetting the drainage operation as in the conventional device. Further, since the power source for operating the solenoid valve for drainage uses the charge of the capacitor charged during the period when the power switch is closed, no voltage remains when drainage is completed. Therefore, unlike a conventional device that operates a solenoid valve by a separate power source, no electric shock accident occurs.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of the device of the present invention, FIG. 2 is a diagram for explaining the operation of the embodiment of FIG. 1, and FIGS. 3 and 4 are other embodiments of the present invention. Fig. 5 is a connection diagram showing an example, Fig. 5 is a sectional view showing the structure of the main part of a water-cooled torch used in the device of the present invention, and Fig. 6 is a piping diagram showing an example of a conventional device. 2 ... Power switch, 3 ... Rectifier circuit, 4 ... Power adjustment circuit, 5 ... Torch, 6 ... Workpiece, 7 ... Torch switch, 8 ... Control circuit, 51 ... Electrode, 52 ... ... Nozzle, 103, 105, 115 ... Solenoid valve, 107 ... Gas pipe, 108, 109 ... Cooling water pipe, 108a ... Branch pipe, C1, C2 ... Condenser, CR1 ... Relay

Claims (2)

[Scope of utility model registration request] 1. In a water-cooled plasma arc machining apparatus for machining a workpiece while cooling water is passed through the torch to cool the torch, a branch for introducing gas provided in the cooling water supply pipe to the torch. Tube, a DC solenoid valve that opens and closes the introduction of gas to the branch pipe, a power supply device that supplies processing power to the torch and the workpiece, and a capacitor that is charged by the supply of power to the power supply device. And a voltage responsive switch that is closed when the supply of electric power to the power supply device is stopped, and a series circuit of the voltage responsive switch and the exciting coil of the DC solenoid valve is connected in parallel to at least the capacitor. A water-cooled plasma arc machining device that constitutes a timed operation circuit of a DC solenoid valve. 2. The DC solenoid valve has a pressure switch closed on the gas supply side due to the presence of gas pressure, and the timed operation circuit of the DC solenoid valve includes a capacitor, the voltage response switch, and the DC solenoid valve. The water-cooled plasma arc processing apparatus according to claim 1, wherein the water-cooled plasma arc processing apparatus is configured by a circuit in which a series circuit including an excitation coil and contacts of the pressure switch is connected in parallel.