RU2458489C1 - Double-jet arc plasmatron - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: double-string arc plasmatron comprises two electrode heads, every of which comprises electrode chambers: a cathode and an anode one, with electrodes, and a nozzle coaxial to an electrode, formed from three electrically insulated diaphragms with cooling channels, in each electrode head the middle diaphragm of the nozzle is arranged with a bore around a nozzle hole at the side facing the head electrode, and with a ledge around the nozzle hole at the opposite side, and in the extreme diaphragms there are the following components: a ledge in accordance with the middle diaphragm bore, or a bore in accordance with the middle diaphragm ledge; in the cathode chamber there is a tungsten electrode-cathode, the working side of which is arranged in the form of a cone, the opposite end of the electrode is arranged in the form of a blade of a flat screwdriver and is installed into a bore of a thrust, which is pressed with a nut, fixed as capable of reciprocal displacement with the help of a threaded joint in a metal bushing installed coaxially to the electrode-cathode 3 in a textolite base of a cathode head; in the anode chamber there is a copper anode arranged as a water-cooled cylinder with a flat working surface.

EFFECT: increased resource of plasmatron operation and higher reproducibility and accuracy of spectral analysis results.

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Description

The invention relates to electrical engineering and analytical instrumentation, and in particular to sources of excitation of the emission spectra of the analyzed samples, and can be used in plasma chemistry to obtain dispersed materials.

A known design of a two-jet arc plasmatron for spectral analysis, containing anode and cathode nodes, each of which contains a housing with a nozzle, a power electrode with a refractory insert placed coaxially with the nozzle, and a device for supplying a plasma-forming gas into the interelectrode chamber formed by the power electrode and the housing with nozzle; the power electrode is made with a through hole and is equipped on one side with a nozzle for supplying plasma-forming gas, and on the other hand with a refractory insert, while the axial hole is connected to the interelectrode chamber by one or more channels enveloping the refractory insert (see RF patent for PM No. 55525 , Н05В 7/18, published on 08/10/2006).

The disadvantages of the known device are:

1) the instability of the plasma jet due to the fact that there is no cooling of the nozzle of each electrode assembly, which in turn leads to the destruction of the nozzle and limits the resource of continuous operation;

2) because of the danger of plasmatron shunting to the nozzle, the nozzle length is limited, and it is known that the spatial and temporal stability of the plasma jet is determined not so much by the localization of the cathode spot (it can be achieved by sharpening the tungsten cathode on the cone), but by the length of the nozzle and its cooling .

Known electric double-arc plasmatron for spectral analysis, which contains two electrode heads (anode and cathode). Each head has an electrode made in the form of a rod, and a nozzle of three diaphragms with cooling channels. The cathode electrode 1 made of tungsten has a long sacrificial part with a thread that connects to the cooled cathode holder 2, the protective gas inlet pipe 3, the plasma gas inlet pipe 4, three copper diaphragms 5, insulators 6, fixing the distance between the electrode and diaphragms, water cooling channels 7, nozzle hole 8; a copper anode 11, made in the form of a water-cooled cylinder with a flat working surface, the input of cooling water 9, the output of cooling water, electrode chambers 12 and 13, where protective gas is supplied (EA No. 006622, Н05В 7/22, publ. 24.02.2006). The device is taken as a prototype.

The disadvantages of the known device are:

- violation of the insulation between the nozzle diaphragms due to burning of the edges of the gaskets facing the plasma, installed between the diaphragms and used to seal the cooling channels and supply plasma-forming and protective gases, as well as to electrically isolate the nozzle diaphragms from each other and from the cathode and anode of the plasmatron. This drawback reduces the life of the plasmatron, requires periodic bulkheads of the plasmatron heads;

- uneven cooling of the nozzle hole, because a channel with cooling water is made in each diaphragm to cool it only on one side of the hole from which the plasma jet flows, which violates the spatial and temporal stability of the plasma torch plasma flow, leads to erosion of the nozzle diaphragm and reduces the life of the plasmatron.

- insufficient contact of the threaded connection of the tungsten electrode - the cathode with the cathode holder, leading to additional erosion of the tungsten cathode.

The technical result of the invention is to increase the service life of the plasmatron and increase the reproducibility and accuracy of the results of spectral analysis.

The technical result is achieved by the fact that in a two-jet arc plasmatron, including two electrode heads, each of which contains an electrode chamber: cathode and anode, with an electrode, and a nozzle of three diaphragms with cooling channels; a tungsten electrode-cathode with an elongated sacrificial part, which is connected to a cooled cathode holder, is installed in the cathode chamber; a copper anode is installed in the anode chamber, made in the form of a water-cooled cylinder with a flat working surface; both electrode heads are equipped with nozzles: shielding gas inlet, plasma-forming gas inlet, coolant inlet and outlet; according to the invention, in each electrode head, the middle diaphragm of the nozzle is made with a groove around the nozzle hole on the side facing the electrode of the head, and with a protrusion around the nozzle hole on the opposite side, and in the proximal diaphragm, there is a protrusion corresponding to the groove of the middle diaphragm a groove is made from the electrode of the diaphragm, corresponding to the protrusion of the middle diaphragm; the dimensions of the groove and protrusion on each diaphragm are coordinated so that the set distance between the nozzle diaphragms along the plasma flow channel is maintained, and the insulating gaskets between the nozzle diaphragms are protected from the glow of the high-temperature plasma flow; cooling channels in the nozzle diaphragms and in the cathode holder are made on three sides around the plasma flow channel; the electrode-cathode on the working side is made in the shape of a cone, the opposite end of the electrode-cathode is made in the form of a flat-blade screwdriver blade and is installed in the stop groove, which is pressed by a nut fixed with the possibility of reciprocating movement with a threaded connection in a metal sleeve mounted coaxially to the electrode cathode in the dielectric base of the cathode head.

The essence of the invention lies in the fact that the nozzle diaphragms of each electrode head form a plasma flow channel such that the insulating spacers installed between the diaphragms are protected from the action of a high-temperature plasma jet and are not subject to destruction. This is achieved by the special design of the diaphragms. A protrusion along the plasma flow channel is made on the middle diaphragm from the exit side of the plasma jet, and a groove is made on the opposite side of the head directed to the electrode. On the diaphragm closest to the electrode, a protrusion is made corresponding to the middle diaphragm groove, at a diaphragm extreme remote from the electrode, a groove is made corresponding to the middle diaphragm protrusion. Between the nozzle diaphragms, the necessary constant clearance is established along the plasma flow channel. The dimensions of the groove and protrusion on each diaphragm are coordinated so that the set distance between the nozzle diaphragms along the plasma flow channel is maintained. This design of the diaphragm nozzle of the plasma heads eliminates the clogging and burning of insulating gaskets installed between the diaphragms.

The cooling channels for the diaphragms with water are designed to bypass the nozzle hole of the plasma flow from three sides, thereby achieving better cooling of the nozzle hole and improving the spatial and temporal stability of the plasma jet in each head.

At the base of the plasma head, coaxial to the electrode, there is a metal sleeve with a thread on its inner surface, along which a nut is moved, resting on a stop pressing the tungsten cathode in the cathode holder, thereby creating the best electrical and thermal contact between the tungsten electrode and the copper cathode holder, cooled by water .

The outermost diaphragm of the nozzle of the cathode and anode heads is made in the form of a cup, in the side walls of which there are four holes with threads along the wall of the cup, the diaphragm is pressed against the base of the plasma head with four screws, thereby creating the necessary sealing of rubber gaskets between the diaphragms.

Figures 1-8 depict the claimed device.

The plasmatron consists of two electrode heads - cathode 1 and anode 2, located at an angle to each other (Fig. 1, Fig. 2). The cathode head 1 (Fig. 2, Fig. 3) contains an electrode-cathode 3 and a nozzle 4 formed by three copper diaphragms 5,6,7. The cathode electrode 3 made of tungsten has a long sacrificial part with a thread, with which it is installed in a cooled copper cathode holder 8. The working surface of the cathode electrode 3 is made in the form of a cone, the opposite end of the electrode 3 is made in the form of a flat blade screwdriver and installed into the groove of the stop 9, which is tightened by a nut 10, mounted with the possibility of reciprocating motion using a threaded connection in a metal sleeve 11, mounted coaxially to the cathode electrode 3 in the textolite base nii 12 cathode heads 1.

The anode head 2 (Fig. 2, Fig. 4) of the plasmatron contains a copper anode 13, made in the form of a water-cooled cylinder with a flat working surface, a flat partition 14 is inserted into the cylinder of the copper anode 13, forming a narrow gap for the cooling water to flow under the flat working surface of the anode .

The cathode 1 and anode 2 of the plasmatron head are equipped with nozzles 15 for introducing coolant and nozzles 16 for outputting coolant (Fig. 5); shielding gas supply pipes 17 and plasma forming gas supply pipes 18 (Fig. 5, Fig. 2).

In the anode casing 13 (Fig. 5, Fig. 6) in the diaphragms of the anode head 19, 6, 7 (Fig. 5), in the cathode holder 8 (Fig. 7) and in the diaphragms 5, 6, 7 of the cathode head (Fig. 5 ) channels 20 are made perpendicular to the plane of the diaphragms 5, 6, 7, the anode housing 13, the cathode holder 8, which serve to supply coolant, and channels 21 for the exit of coolant; the channels 22 (Fig. 6, 7, 8) are made in the plane of the diaphragms 5, 6, 7, 19 around the nozzle hole 4, in the plane of the cathode holder 8 around the tungsten electrode 3, in the plane of the anode body 13 from the channel 20 to the partition 14 and from the partition 14 to channel 21.

Channel 23 (Fig. 7, 6) serves to supply the protective gas to the electrode chamber formed by the cathode electrode 3 and the diaphragm 5 in the cathode head 1, and to the electrode chamber formed by the anode 13 and diaphragm 19 in the anode head 2. Channel 24 ( Fig. 6, 7) serves to supply a plasma-forming gas between the diaphragms of the nozzle heads.

Rubber gaskets 25 are used to seal the coolant supply channels, protective and plasma-forming gases. The diaphragms 7 of each electrode head are made in the form of a glass (Fig. 3, 4, 5), in the side walls of which four holes 26 are made with thread along the glass wall. Using four screws 27, the diaphragm 7 of the nozzle 4 is attached to the textolite base 12 of the plasma head, creating the necessary seal of the rubber gaskets 25 between the cathode holder 8 and the diaphragm 5 in the cathode head, the anode 13 and the diaphragm 5 of the anode head 2 and between the diaphragms 5, 6, 7, 19 nozzle heads 1 and 2. In all three diaphragms of the nozzles of both heads, a groove 28 is made around the nozzle hole 4 from the side facing the electrode. Diaphragms 5 and 6 in the cathode head and diaphragms 19 and 6 in the anode head are made with a conical protrusion 29 around the nozzle hole 4 (Fig. 2, Fig. 3, Fig. 4). The dimensions of the groove 28 and the protrusion 29 in each head are coordinated so that the set gap between the diaphragms is maintained and the gaskets 25 are not exposed to light from the plasma jets.

The device operates as follows.

Shielding gas is supplied to the electrode chambers of heads 1, 2 through nozzles 17, and plasma-forming gas is supplied through nozzles 18. Coolant is supplied through the nozzles 15 (Fig. 5), which enters the channels 20, and then the nozzle opening 4 flows around the channels 22, enters the channels 21 and leaves the electrode head through the nozzle 16. The electrodes 3 and 13 are supplied with voltage from the rectifier. Using a trigger device (A.P. Tagiltsev, E.A. Tagiltseva "Automatic start of a two-jet arc plasmatron. Factory laboratory. Diagnostics of materials. No. 3. 2009, volume 75, pp. 23-25. Fig. Not shown) auxiliary arcs between the electrode and the diaphragms of the nozzle in each head are ignited, plasma jets are blown out of the nozzles of the heads and when they merge, the main arc between the cathode and anode is ignited, the start circuits are disconnected.

Thus, the new structural elements of the claimed device can increase the service life of the plasmatron and increase the reproducibility and accuracy of the results of spectral analysis.

Claims (1)

Two-arc arc plasmatron, including two electrode heads, each of which contains electrode chambers: cathode and anode, with electrodes and a nozzle, coaxial with the electrode, formed of three electrically insulated diaphragms with cooling channels; a tungsten electrode-cathode with an elongated sacrificial part, which is connected to a cooled cathode holder, is installed in the cathode chamber; a copper anode is installed in the anode chamber, made in the form of a water-cooled cylinder with a flat working surface; both electrode heads are equipped with nozzles: shielding gas inlet, plasma-forming gas inlet, coolant inlet and outlet, characterized in that in each electrode head the middle diaphragm of the nozzle is made with a groove around the nozzle hole on the side facing the electrode of the head and with a protrusion around the nozzle holes on the opposite side, and in the extreme diaphragms are made: a protrusion, respectively, the groove of the middle diaphragm or a groove, respectively, the protrusion of the middle diaphragm; the dimensions of the groove and protrusion on each diaphragm are coordinated so that the set distance between the nozzle diaphragms along the plasma flow channel is maintained, and the insulating gaskets between the nozzle diaphragms are protected from the glow of the high-temperature plasma flow; cooling channels in the nozzle diaphragms and in the cathode holder are made on three sides around the plasma flow channel; the electrode-cathode on the working side is made in the shape of a cone, the opposite end of the electrode-cathode is made in the form of a flat-blade screwdriver blade and is installed in the stop groove, which is pressed by a nut fixed with the possibility of reciprocating movement with a threaded connection in a metal sleeve mounted coaxially with cathode electrode in the dielectric base of the cathode head.

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