CN1051490C - Electric are cutting machine - Google Patents
Electric are cutting machine Download PDFInfo
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- CN1051490C CN1051490C CN96112841A CN96112841A CN1051490C CN 1051490 C CN1051490 C CN 1051490C CN 96112841 A CN96112841 A CN 96112841A CN 96112841 A CN96112841 A CN 96112841A CN 1051490 C CN1051490 C CN 1051490C
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Abstract
The present invention relates to an electric arc cutting machine which is provided with an AC-DC conversion device for converting an AC power supply into a DC power supply, wherein the output of the AC-DC conversion device is converted into high frequency output by an invertion device, and a rectifying device is used for converting the high frequency output into DC output. The rectifying device is provided with a first and a second output terminals. The first output terminal is connected with a first terminal which can be connected with a workpiece, and the second output terminal is connected with a second terminal which can be connected with a cutting torch cathode. An arc strike generator is arranged between a third terminal connected with the cutting torch anode and the second terminal, and the arc strike generator comprises a high frequency generator.
Description
The present invention relates to produce the arc cutting machine of electric arc, the holding circuit of the especially relevant current-limiting resistor that in arc cutting machine, uses by striking.
When utilization produces the arc cutting machine cut workpiece of electric arc by striking,, make from the striking electric current of dc source and between the negative electrode of cutting torch and anode, flow through at first by between the negative electrode of the cutting torch of the short space setting of being separated by and anode, producing high-frequency discharge.In order to limit the striking electric current, be provided with current-limiting resistor.When flowing through the striking electric current, current-limiting resistor just has electric current to flow through.For making the arc cutting machine miniaturization, current-limiting resistor also will use small-sized.Therefore, if the guiding arc current repeatedly flows through current-limiting resistor, then current-limiting resistor will be heated unusually, thereby the utilization rate of current-limiting resistor is reduced.For this reason, in arc cutting machine, be provided with the holding circuit of current-limiting resistor.
In the past, as the arc cutting machine of the holding circuit that is provided with current-limiting resistor, pattern was as shown in Figure 1 arranged.In this arc cutting machine, be transformed to DC voltage by transverter 4 from the alternating voltage of AC power 2.This DC voltage is transformed to the low pressure high frequency voltage by inverter 6.This high frequency voltage is transformed to DC voltage by rectification circuit 8.
As transverter 4, for example can use the type that has diode and smmothing capacitor.As inverter 6, for example can use power fet or IGBT (igbt).As rectification circuit 8, identical with transverter, can use the structure that has diode and smmothing capacitor.
From the positive terminal 8a of rectification circuit 8 to capacitor 20 with the tie point of high-frequency coupling coil 22, connecting the series circuit of switch 26 and current-limiting resistor 28.That is, current-limiting resistor 28 is connected with switch 26, high-frequency coupling coil 22, cutting torch anode 15b, cutting torch negative electrode 15a, is connected between terminal 8a, the 8b of rectification circuit 8.On current-limiting resistor 28, be arranged in parallel the series circuit that the relay coil 34a by Zener diode (zenerdiode) 30, resistor 32, relay 34 forms.Capacitor 36 is being connected in parallel on relay coil 34a.Relay coil 34a when supplying with the voltage of regulation at its two ends, disconnects the normally closed contact 34b that is connected in controller 38.Above-mentioned Zener diode 30, resistor 32, relay coil 34a, capacitor 36, relay tip 34b constitute the current-limiting resistor holding circuit.
In this arc cutting machine, be transformed to DC voltage by transverter 4 from the alternating voltage of AC power 2.This DC voltage is transformed to the high frequency low-voltage by inverter 6, and is transformed to DC voltage by rectification circuit 8.Why using inverter 6, is for fear of using large-scale transformer.
Initial stage after this arc cutting machine starting, owing between cutting torch negative electrode 15a and workpiece 14, do not produce electric arc, so there is not electric current to flow to cutting torch 15 sides from rectification circuit 8.At this moment, as with switch 44 closures, then controller 38 is devoted oneself to work high frequency generating apparatus 24.Thereby make high-frequency pulse signal flow back into high-frequency coupling coil 22 from high-frequency coupling coil 22 through cutting torch anode 15b, cutting torch negative electrode 15a, capacitor 20 by the cycle of each regulation.In view of the above, produce high-frequency discharge between cutting torch negative electrode 15a, cutting torch anode 15b, impedance between the two reduces.At this moment, the striking electric current produces striking from the negative terminal 8b that positive terminal 8a process switch 26, current-limiting resistor 28, high-frequency coupling coil 22, cutting torch anode 15b, the cutting torch negative electrode 15a of rectification circuit 8 flows to rectification circuit 8 between cutting torch anode 15b and cutting torch negative electrode 15a.
In this state, as with cutting torch 15 close workpiece 14,, then between cutting torch negative electrode 15a and workpiece 14, produce arc discharge owing to exist striking.Consequently, arc current flows to the negative terminal 8b of rectification circuit 8 by current transformer the 42, the 1st terminal 10, workpiece 14, cutting torch negative electrode 15a, the 2nd terminal 12 from the positive terminal 8a of rectification circuit 8.After this arc current was detected by current transformer 42, controller 38 disconnected switch 26, stoped electric current to flow through current-limiting resistor 28, and meanwhile, controller 38 quits work high frequency generating apparatus 24.
, cutting machine is the equipment that is used for cutting off workpiece, so after the cutting of finishing workpiece 14, the positive terminal 8a of rectification circuit 8 and the circuit between the negative terminal 8b are disconnected, electric arc disappears.Therefore, current transformer 42 detects does not have arc current to flow through, and controller 38 with switch 26 closures, makes high frequency generating apparatus 24 start working according to this testing result simultaneously.Therefore, same as described above, produce electric arc once more.That is, carry out restarting of striking cutting machine.For example, when the workpiece that is cut 14 when netted, the disappearance of electric arc will can frequently take place at short notice.Therefore, as repeatedly restarting at short notice, then will be quite long in the cumulative time of current-limiting resistor 28 upper reaches overcurrent.For making the cutting machine miniaturization, current-limiting resistor 28 also will use small-sized low capacity, so current-limiting resistor 28 might burn because of unusual heating.Therefore, can not flow through electric current at short notice continually if use on the current-limiting resistor 28.In addition, when using the frequent Closing Switch 44 of the people of this guiding arc cutting machine, also there is same situation.
Therefore, be provided with the holding circuit of current-limiting resistor 28.When the voltage of supplying with on Zener diode 30 at the electric current that flows through on the current-limiting resistor 28 surpassed the breakdown voltage of Zener diode 30, capacitor 36 was by resistor 32 chargings.When current-limiting resistor 28 did not have electric current to flow through, capacitor 36 was by resistor 32 and current-limiting resistor 28 discharges.Capacitor 36 is recharged at short notice continually, and its charging voltage is as reaching the operation voltage of relay 34, and then relay coil 34a disconnects relay tip 34b.In view of the above, controller 38 quits work inverter 6, along with the disappearance of electric arc, even high frequency generating apparatus 24 produces high-frequency impulse, does not also have electric current and flows through current-limiting resistor 28.
In this holding circuit owing to use relay 34, resistor 32, Zener diode 30, institute so that arc cutting machine maximized.And the operation voltage of relay 34 (off voltage of relay tip 34b) changes with its environment temperature.In addition, for operation voltage being supplied with the resistor 32 that relay coil 34a adopts and the value of capacitor 36, also change with environment temperature.Be configured near relay 34 current-limiting resistors 28 and also sending sizable heat.Therefore, the voltage change that the relay tip 34b of relay 34 is disconnected is very big.Want to prevent this variation, even must use environment temperature to change the product that its value also is difficult to change to resistor 32 and capacitor 36, yet its price is very high.The Japanese patent application No.HEI 1-197063 that on August 8th, 1989 published discloses the circuit except that the current-limiting resistor holding circuit shown in Figure 1, and the current-limiting resistor holding circuit itself is a known technology.
The purpose of this invention is to provide a kind of arc cutting machine that can protect current-limiting resistor with low cost accurately.
Arc cutting machine of the present invention has the alternating continuous-current commutating machine that AC power is transformed to dc source.The output of this alternating continuous-current commutating machine is transformed to high frequency output by inverter.The high frequency output transform that is provided with in this arc cutting machine this inverter is the fairing of direct current output.Fairing has the 1st and the 2nd lead-out terminal.The 1st lead-out terminal is connected in the 1st terminal.The 1st terminal can be connected with workpiece.The 2nd lead-out terminal is connected in the 2nd terminal.The 2nd terminal can be connected in the cutting torch negative electrode.And, on this striking cutting machine, also be provided with the 3rd terminal that can be connected with cutting torch.Between the 2nd terminal and the 3rd terminal, be provided with the striking generating means.This striking generating means comprises high frequency generating apparatus.Between the 1st and the 2nd lead-out terminal of fairing, be provided with cutting torch negative electrode, cutting torch anode, reach the current-limiting resistor that high frequency generating apparatus is connected in series.The voltage that is provided with according to these current-limiting resistor two ends makes the out-of-work current-limiting resistor protective device of inverter.
This current-limiting resistor protective device have when electric current flows through current-limiting resistor, carry out ascending order counting, when not having electric current to flow through current-limiting resistor, carry out the statoscope counting apparatus of descending counting.If the count value of this statoscope counting apparatus surpasses setting value, then produce and make inverter withdraw from service signal.
The current-limiting resistor protective device can also be provided with and generate the signal that constitutes the 1st state, the current sensing means that generates the signal that constitutes the 2nd state when not having electric current to flow through current-limiting resistor when electric current flows through current-limiting resistor.When the signal of this current sensing means was the 1st state, the statoscope counting apparatus carried out the ascending order counting, and when the signal of this current sensing means was the 2nd state, the statoscope counting apparatus carried out the descending counting.
In addition, the count value that rising progressively of statoscope counting apparatus time per unit counted changes the count value variation greater than count down.Say that more specifically when importing the clock pulse signal of certain frequency, the statoscope counting apparatus just carries out ascending order counting or descending counting, the count number during the ascending order counting can be greater than the descending count number.In addition, when input clock pulse signals, the statoscope counting apparatus only carries out the ascending order counting or the descending counting of same count amount, but the frequency of the clock signal that descending can be counted is selected in than the low degree of ascending order counting.
Fig. 1 is the block diagram that has the arc cutting machine of existing current-limiting resistor.
Fig. 2 is the figure of the high-frequency pulse signal of expression high frequency generating apparatus generation shown in Figure 1.
Fig. 3 is the block diagram of an embodiment of the arc cutting machine behind enforcement the present invention.
Fig. 4 is the action flow chart that is illustrated in the statoscope counting apparatus that uses in the arc cutting machine of Fig. 3.
Fig. 5 is the time diagram of the striking cutting machine of Fig. 3.
Fig. 6 is other example block diagram of statoscope counting apparatus.
Fig. 7 is the block diagram of another example of statoscope counting apparatus.
Fig. 8 is the time diagram of the arc cutting machine behind employing Fig. 7 statoscope counting apparatus.
As shown in Figure 3, present embodiment is except that the holding circuit of current-limiting resistor, and is identical with the structure of the existing arc cutting machine that utilizes striking generation electric arc shown in Fig. 1, identical part is marked with prosign, and its explanation is omitted.
The holding circuit of current-limiting resistor 28 has the detector 50 that is used for the voltage between detectability flow resistor 28 two ends.When because when producing voltage flowing through the striking electric current on the current-limiting resistor 28 between the two ends of current-limiting resistor 28, this detector 50 produces the 1st state, for example high level output signal.And when because when not flowing through the striking electric current thereby not producing voltage on current-limiting resistor 28, this detector 50 produces the 2nd state, for example low-level output signal.As this detector 50, for example can use the comparator that voltage and reference voltage between the two ends of current-limiting resistor 28 (for example 0V) are compared.
The output signal of detector 50 supplies to statoscope counting apparatus, for example statoscope counting apparatus 52.This statoscope counting apparatus 52 for example also can be made of with microcomputer controller 38, or also can be made of programmable logic device (Programmbale Logic Device) PLD.
That is, at first, judge whether the output level of detector 50 is high level (step S2).Output level as detector 50 is a high level, then because of flow through the striking electric current on current-limiting resistor 28, so add predetermined number C1 on the count value C of the counter that is made of software, for example only adds+10 (step S14).When to this arc cutting machine supply power, the count value C of this counter is set to 0.
In addition, in step S2, not high level as the output level of judging detector 50, then on current-limiting resistor 28, do not flow through the guiding arc current.Therefore, deduct predetermined number C2,6 (step S6) for example from count value C.Then, whether judge count value C greater than 0 (step S8), C is not more than 0 as count value, makes then that count value C is 0, and finishes the action of statoscope counting apparatus.
For example, in the moment to this arc cutting machine supply power, also do not flow through the striking electric current, the output level of detector 50 is a low level.Under this state, as execution in step S6, then whenever producing clock pulse signal, just the count value of counter reduces gradually from 0.Then, even the striking electric current produces, the count value of counter increases, and its count value C also is not easy greater than 0 very much.Consequently, count value C can not correctly represent the febrile state of current-limiting resistor 28.For preventing this situation, be provided with step S8, S10, prevent that count value C is less than 0.
After step S4 or S8, judge that count value C is whether more than setting value (step S12).If count value C more than setting value, does not then make the release of this statoscope counting apparatus.Therefore, when the clock pulses signal rises, be high level as the output level of detector 50, promptly, as flow through the striking electric current on current-limiting resistor 28, count value C adds 10, is low level as the output level of detector 50, that is, do not flow through the striking electric current, then count value C subtracts 6 one by one.But count value can not be less than 0.As a result, this count value C can represent the febrile state of current-limiting resistor 28 indirectly.Why the descending count value is less than the ascending order count value, is because even without flowing through the striking electric current, but the reduction of the temperature of current-limiting resistor 28 is to rise with temperature to carry out with identical speed, not equal to temperature reduces than the temperature cause slowly that rises.
And setting value is that the caloric value of determining after the caloric value of burning possibility being arranged and count suitable safety coefficient when current-limiting resistor 28 being flow through the striking electric current is determined.Count value C is as surpassing this setting value, just then statoscope counting apparatus 52 makes inverter 6 out-of-work signals (step S14) to controller 38 supplies.Controller 38 stops inverter 6 according to this signalizing activity.Consequently, between the sub-8a of the positive-negative output end of fairing 8,8b, do not produce DC voltage, on current-limiting resistor 28, do not have electric current to flow through yet, can prevent the unusual heating of current-limiting resistor 28.Then, make count value C equal setting value (step S16), finish the action of statoscope counting apparatus 52.Even the caloric value of current-limiting resistor 28 increases, the variable quantity of count value C does not change yet, and when flowing through the striking electric current, is+10 when not guiding arc current when flowing through, to be-6.Therefore, count value C can represent the febrile state of current-limiting resistor 28 with high accuracy.
In addition, at step S16, why make count value C equal setting value, its reason is as follows.For example, as allow that count value C gets the value greater than setting value, though then in fact corresponding with setting value caloric value is the heating of current-limiting resistor 28, the beginning count value of descending counting becomes the value bigger than setting value.The result will become makes count value produce reasons of error.
The time diagram of this arc cutting machine shown in Figure 5.This figure (a) represents clock signal, this figure (b) expression is shorter when the striking current intervals time, but the output signal of detector 50 when flushing time is longer, this figure (c) expression was lacked but the count value of flushing time statoscope counting apparatus 52 when longer when the blanking time of striking electric current.Can clearly be seen that from Fig. 5 (b), (c), shorter when the blanking time of striking electric current, but flushing time is when longer, and count value C can not reach setting value.Like this, in the present embodiment, if be 1 unit interval during from a clock pulse signal rising edge to next clock pulses rising edge, then the variable quantity of the count value of the statoscope counting apparatus 52 in during this period serves as big when counting with ascending order.
This figure (d) expression is when frequently disappearing owing to electric arc, thereby make the also output signal of detector 50 in short-term of the short and flushing time of striking current intervals, this figure (e) expression when the striking current intervals short and flushing time also in short-term the count value of statoscope counting apparatus 52 change.At this moment, owing to there is the striking electric current under the condition of the time interval, to flow through,, quit work at this moment inverter 6 so count value reaches setting value than weak point.Therefore, do not produce voltage on the sub-8a of the positive-negative output end of fairing 8,8b, shown in this figure (d), the output signal of detector 50 becomes low level.
In the above-described embodiments, the statoscope counting apparatus is made of microcomputer or PLD.But, also can use the statoscope counting apparatus 52a that constitutes by hardware as shown in Figure 6.
This statoscope counting apparatus 52a be one adopt 2 adders 54,56, storage part 58, " or " integrator of circuit 60, phase inverter 62.
When supplying with low level signal on starting terminal 64,66, adder 54,56 can work.And, supply with on the startup terminal 64 of adder 54 be by phase inverter 62 with the output signal of detector 50 signal after anti-phase.What supply with on the startup terminal 66 of adder 56 is the original output signal of detector 50.
When the startup terminal 64 of adder 54 for low level, be that the output level of detector 50 is the clock signal of high level certain frequency when rising, will institute's signal supplied addition on 2 input terminals of adder 54.On an input terminal of adder 54, supply with the output signal of storage part 58, supply with+10 on another input terminal.Therefore, when the output level of detector 50 is high level and clock pulse signal when rising, the output of adder 54 increases one by one+and 10.
When the startup terminal 66 of adder 56 for low level, be detector 50 when being output as the low level clock pulse signal and rising, will institute's signal supplied addition on 2 input terminals of adder 56.On an input terminal of adder 56, supply with the output of storage part 58, for example register, supply with-6 on another input terminal.Therefore, when the output signal of detector 50 is low level and clock pulse signal when rising, the output of adder 56 subtracts 6 one by one.The output of adder 54,56 by " or " circuit 60 supplies with storage parts 58, whenever clock pulse signal rises, just should the time by " or " the circuit signal supplied stores.Therefore, when adder 54 work, its output is stored in the storage part 58, and when adder 56 work, its output is stored in the storage part 58.Then, the output of this storage part 58 compares with setting value in comparator 68, surpasses setting value as the storing value of storage part 58, and then comparator 68 is to controller 38 output inverter stop signals.At this moment time diagram is the same with the situation of Fig. 5.
In addition, as shown in Figure 7 and Figure 8, also can frequency of utilization different 2 clock signal clk1 and clk2 constitute statoscope counting apparatus 52b.That is use commercially available up-down counter 70 as shown in Figure 7.On this up-down counter 70, supply with the signal of self-detector 50.When this signal was high level, up-down counter 70 carried out the ascending order counting, and when this signal was low level, up-down counter 70 carried out the descending counting.This liter or fall counting is all gone up at the clock terminal (clk) of up-down counter 70 and is carried out when the clock signal of supplying with rises.Clock signal by " or " circuit 72 supplies with clock terminals." with " output signal of circuit 74,76 supply with " or " circuit 72." with " supply with the high clock pulse signal clk1 of frequency that Fig. 8 (a) illustrates and the output signal of detector 50 on the circuit 74." with " supply with on the circuit 76 the low clock pulse signal clk2 of frequency that Fig. 8 (b) illustrates, and by phase inverter 78 with the output of detector 50 signal after anti-phase.In the present embodiment, the frequency of clk1 is 2 times of clk2 frequency.The relation of the frequency of two clock pulse signals is not limited thereto, and can set arbitrarily.
Owing to adopt said structure,, carry out the ascending order counting action shown in Fig. 8 (d) fast so when detector 50 was output as high level, when promptly carrying out the ascending order counting, high-frequency clock signal clk1 supplied with up-down counter 70.When detector 50 was output as low level, when promptly carrying out the descending counting, low-frequency clock pulse signal clk2 supplied with up-down counter 70, shown in Fig. 8 (d), carried out descending counting action slowly.
That is,, carry out the ascending order counting fast, stop electric current supply, but the state that the reduction of temperature can not be carried out is rapidly slowly simulated by making the descending counting current-limiting resistor 28 when electric current flows through current-limiting resistor 28 and adstante febre.As the time of supposition from the rising edge of clk2 to the rising edge of next clk2 be the unit interval, then the ascending order count number of unit interval is greater than the count down amount of unit interval.
In addition, the count value of up-down counter 70 is predisposed to setting value if surpass setting value then to controller 38 output inverter stop signals, and with count value.The count value of up-down counter 70 then is predisposed to 0 with count value if change to below 0.
In the above-described embodiments, current transformer 42 is located between lead-out terminal 8a and the 1st terminal 10, but also can be located between lead-out terminal 8b and the 2nd terminal 12.
Claims (5)
1. an arc cutting machine comprises: the alternating continuous-current commutating machine that AC power is transformed to dc source; The output signal of this alternating continuous-current commutating machine is transformed to the inverter of high frequency output; With the high frequency output transform of this inverter is direct current output and the fairing with the 1st and the 2nd lead-out terminal that produces direct current output; The 1st terminal that is connected in this fairing the 1st lead-out terminal and can be connected with workpiece; Be connected in the 2nd lead-out terminal of above-mentioned fairing and the 2nd terminal that can be connected with the cutting torch negative electrode; The 3rd terminal that can be connected with cutting torch; Be arranged between above-mentioned the 2nd terminal and the 3rd terminal and comprise the striking generating means of high frequency generating apparatus; With cutting torch negative electrode, cutting torch anode, and high frequency generating apparatus be connected in series in current-limiting resistor between the 1st and the 2nd lead-out terminal of fairing; And it is corresponding with the voltage between these current-limiting resistor two ends; make the out-of-work current-limiting resistor protective device of above-mentioned inverter; it is characterized in that; the current-limiting resistor protective device has the statoscope counting apparatus; this statoscope counting apparatus carries out the ascending order counting when electric current flows through current-limiting resistor, carry out the descending counting when not having electric current to flow through current-limiting resistor; surpass setting value as its count value, then produce the signal that above-mentioned inverter is stopped transport.
2. arc cutting machine according to claim 1; it is characterized in that: above-mentioned current-limiting resistor protective device has the current sensing means that generates the signal of formation the 1st state when electric current flows through current-limiting resistor, generate the signal that constitutes the 2nd state when having electric current to flow through current-limiting resistor; when the signal of this current sensing means is the 1st state; above-mentioned statoscope counting apparatus carries out the ascending order counting; when the signal of above-mentioned current sensing means was the 2nd state, above-mentioned statoscope counting apparatus carried out the descending counting.
3. arc cutting machine according to claim 1 is characterized in that: make the count value of the ascending order counting of above-mentioned statoscope counting apparatus in its time per unit change the count value variation of counting greater than the descending of time per unit.
4. arc cutting machine according to claim 1 is characterized in that: when input clock signal, above-mentioned statoscope counting apparatus just carries out ascending order counting or descending counting, and the count number during the ascending order counting is greater than the descending count number.
5. arc cutting machine according to claim 1, it is characterized in that: when input clock signal, above-mentioned statoscope counting apparatus carries out ascending order counting or descending counting, and ascending order counting count number equates with the descending count number, the frequency of the clock signal that above-mentioned descending is counted low degree when being selected in and counting than ascending order.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96112841A CN1051490C (en) | 1996-09-20 | 1996-09-20 | Electric are cutting machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96112841A CN1051490C (en) | 1996-09-20 | 1996-09-20 | Electric are cutting machine |
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| Publication Number | Publication Date |
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| CN1177530A CN1177530A (en) | 1998-04-01 |
| CN1051490C true CN1051490C (en) | 2000-04-19 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN96112841A Expired - Lifetime CN1051490C (en) | 1996-09-20 | 1996-09-20 | Electric are cutting machine |
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| WO2014086636A1 (en) | 2012-12-04 | 2014-06-12 | Sulzer Metco Ag | Method and control device for operating a plasma generation device |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1071358A (en) * | 1992-10-17 | 1993-04-28 | 张孟荣 | Ultra-small inversion energy-saving air plasma cutting machine |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1071358A (en) * | 1992-10-17 | 1993-04-28 | 张孟荣 | Ultra-small inversion energy-saving air plasma cutting machine |
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