US3206587A

US3206587A - Plasma-jet-gun

Info

Publication number: US3206587A
Application number: US258328A
Authority: US
Inventors: Kugler Tibor; Vesely Vladimir
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-02-13
Filing date: 1963-02-13
Publication date: 1965-09-14
Anticipated expiration: 1982-09-14

Description

Sept. 14, 1955 'r. KUGLER ETAL PLASMA-JET-GUN 2 Sheets-Sheet 1 Filed Feb. 13, 1963 INVENTOR- y/w %9/e/; Ward/Z710 flue/y P 1965 1-. KUGLER ETAL 3,206,587

PLASMA-JET-GUN Filed Feb. 13, 1963 2 Sheets-Sheet 2 FIG. 2.

INVENTORS 7/2 0/ 5 02/5 Mad/ImfifiJe/y Wa w United States Patent 3,206,587 PLASMA-JET-GUN Tiber Kugler, 2 Zelena, Prague 6, Czechoslovakia, and Vladimir Vesely, 286 Komenskeho, Revnice, Czechoslovakia Filed Feb. 13, 1963, Ser. No. 258,328 8 Claims. (Cl. 219-75) The invention relates to a plasma-jet-gun for heat treatment of various materials, more particularly, for depositing coatings from high-melting materials, where the electrodes are specially arranged for resisting erosion by an electric arc and where the chambers housing the electrodes are sealed against plasma gas leakage. This plasma-jetgun is suitable for application in machine construction works, in metallurgy and chemistry, especially for coatings resistant to heat, abrasion and corrosion influences.

For these purposes, up to now, use has been made of plasma-jet-guns working with inert gases and having a tungsten interior electrode and an exterior electrode provided 'by the outlet nozzle. Besides, application has been made of plasma-jet-guns having a vortex surrounding the electric arcs trunk, and having a carbon interior electrode.

These appliances are disadvantageous because the plasma-jet-guns utilizing inert gases for the plasma generating possess a low thermal efficiency, exceeding seldom 50%, and require considerable operating expenses. The use of an outlet nozzle as the exterior electrode does not allow to use more than ten percent of hydrogen. It is well known that the thermal efficiency of the heated material increases with the increase of hydrogen content within the plasma. In case of liquid plasma-jet-guns including a carbon electrode, automatic regulation must be provided for shifting ahead the carbon electrode which gets consumed at a relative quick rate and must be replaced very often. The whole construction is, therefore, much more complicated in design.

Accordingly, an object of the present invention is to overcome the foregoing difliculties and disadavantages by providing cooled, metallic, rotating electrodes, the consumption whereof is substantially lower than that of the carbon electrodes. The advantage well known in regard of liquid plasma-jet-guns, namely the high energetic eificiency and the presence of a considerable amount of hydrogen in the plasma, are combined in this way with those advantages known in respect of gas pla-sma-jet-guns, namely, the low wear of the electrodes and the lack of provision of means for automatic shifting of the electrode.

In accordance with the present invention, the plasmajet-gun includes the interior electrode in form of a cooled metallic ring rotating about an axis parallel to the channel surrounding the burning electric are. This ring is mounted upon a carrier and on the periphery whereof a series of blades is arranged and forms a revolving liquid seal from the liquid having entered the space surrounding the electrode which they set in movement. This seal stands in way to leakage of the plasma gas from the electrodes chamber and holds the liquid therein at such a level that it does neither fill up the electrodes chamber, nor extinguish the electric arc. The liquid may be recirculated into the vortex surrounding the electric arc. Depending on the material of the electrode, an additive gas is conducted into the chamber surrounding the interior electrode through a special channel and orifice. In cases where the material utilized either is nonconductive, or cannot be attached to the source of the electric current, the invention proposes the use of an exterior rotating electrode situated at the outlet of the plasma from the gun. The electrodes thus have a Substantially larger area than the area of the foot of the electric arc, and this foot is then in touch with any place of the surface of the electrodes during a short period only. Consequently, the wear of the electrodes is reduced even where hydrogen is present in the plasma gas in a relatively larger proportion. The increased dimensions of the electrodes, as compared with the diameter of the plasma stream, make possible to place upon the electrodes a greater fluid amount of material and to yet prolong their lifetime. This arrangement makes also superfluous any care for automatic shifting of the electrodes towards the electric arc. The dimensions of the electrodes can be chosen so that there can exist, side by side, several trunks of electric arcs, each of which burns Within a separate channel.

Embodiments of the invention have been chosen for purposes of illustration and description, and are shown in the accompanying drawing, forming a part of the specification, wherein:

FIG. 1 is a sectional view of a plasma-jet-gun provided with rotating interior and exterior electrodes with the exterior electrode in form of a disc placed so that the foot of the electric arc touches the outer circumference of the disc. Both electrodes are made of metal.

FIG. 2 is a sectional view of another embodiment according to the invention, including the same interior electrode as shown in FIG. 1, but having the exterior electrode constructed and arranged so that the foot of the electric arc touches its inner circumference.

In the embodiment according to FIG. 1, the stabilization of the trunk of the electric arc is achieved within the channel with screens 3, 4 and 6, mounted within a block 7 made of an insulating material. The cylindrical zone of the screen 4 includes tangential orifices 20 and 22 wherethrough a channel 21 feeds-in the working liquid. In the alternative, the cylindric zone of the screen 4 adjacent the screen 6 can include a tangential orifice 5 feeding-in the working liquid from the chamber of a interior electrode 10. This is accomplished by a metallic ring attached in electrially conductive manner upon a rotating carrier 12 which bears blades 8 extending forwardly from a flange 9. The carrier 12 contains a conduct for the cooling liquid and a cylindrical zone serving for furnishing the current from a brush 15. A shaft 14 of the carrier 12 lies in a bearing 13 of the block 7. This block 7 contains a channel 18 serving to lead gas into the chamber surrounding the interior electrode 10. The chamber surrounding the interior electrode 10 is provided with an outlet 16 serving for the liquids outflow. An exterior metallic rotating electrode 23 situated in a bearing 19 in the block and provided with a current conductor 17 is mounted upon the carrier 12 over an insulating insert 11. A chamber 24 closed by a packing 25 serves for leading the cooling liquid into the hollow electrode 23. In front of the outlet screen 3, a baffle or diffuser 1 is placed which is provided with the orifice 2 for the liquids outflow.

In the embodiment illustrated in FIG. 2, an exterior electrode 32 formed by a metallic ring bearing blades is connected across a metallic cylinder 34 and an insulating insert 35 within a carrier 40 of an interior electrode 41. In construction, the design of the interior electrode 40 is generally identical with that of the embodiment shown in FIG. 1. The electric current is fed to the exterior electrode 32 by a brush 50, and to the interior electrode by a brush 46. The system of electrodes is housed by an insulating block 31. The stabilization channel is formed by screens 36, 37, and 38, and is placed within an insulating block 55. The screens 36 and 38 are provided with outlets 57 and 56 through which the liquid flowing from the channel is lead away. The block 55 is placed concentrically with the system of electrodes so that there remains between it and the insulating insert 35 a sufficient gap allowing the liquid to flow through. In the block 55, a channel 54 with a branch 48 serves for leading the liquid into the stabilizing zone and includes a branch 47 leading the liquid into the carrier 40 of an electrode 41 through an orifice 43.

Channels

53 and 49 serve for conducting gas into the chamber surrounding the interior electrode 41. The channels 51 and 52 lead the liquid out of the gap between the insulating cylinder 35 and the block 55.

The apparatus according to the invention shown in FIG. 1 works so that, in the region between the interior electrode 10 and the exterior rotating electrode 23, the electric arc burns within the channel formed by the liquid vortex. Through a conduit 18 along the electrode 10, a gas can be fed in addition. The quantity and kind of this gas are fixed by technologic requirements and by the art of the metal whereof the electrode 10 is manufactured. It is well known that the erosive action of the electric arc causes abrupt wear upon electrodes made of certain kinds of metallic materials, and that this wear can be substantially reduced when hydrogen is not allowed to come in any greater concentration in immediate proximity of the electrodes. Where use was made of certain metallic materials, it is, besides, highly advantageous to form a tin oxide layer upon their surface. Hereto, it will suflice a gas, e.g. the air, in such a small quantity only which does not influence in excess the concentration of hydrogen in the outfiowing plasma stream. The presence of a non-condensing gas retards, besides, the condensation of plasma vapours within the electrodes chamber, so that the energy of the plasma is prevented from being conducted into the liquid in the chamber of the interior electrode 10. From the channel, a part of the liquid flows over the surface of the screen 6 into the electrodes chamber where the blades 8 induce it into rotating movement. In this way, this liquid and that one which flows through the channels in the carrier 12, form, in the periphery of the chamber, a liquid ring which stops any leakage of the gas from the electrode chamber. The liquid of this ring is lead away through the orifice 16. Where the revolution of the electrodes has been chosen so that centrifugal forces give the liquid ring a sufiiciently high pressure, the outflow, instead of ensuing through the orifice 16, may be carried out through the channel which conducts thereafter the liquid into the vortex movement Within the channel area. In coming into the vortex in this case, the liquid is already preheated so that heat losses are lowered considerably. The possibility to exploit sufficiently rapid revolution of the electrodes depends on physical and mechanical properties of the construction material of the carrier 12, and on electric properties of the materials of the electrodes 10 and 23 which must allow sutficiently quick movement of the respective electrode under the foot of the electric arc, without adversely affecting its stability. The liquid for cooling the exterior electrode 23, and the interior electrode 10, is fed through the chamber 24 sealed-up by packing 25, across the hollow electrode 23 and through its hollow shaft towards the electrode 10. The liquid flowing out of the channel over the surface of the screen 3 is lead away by bafiling action of the ditfusor 1 towards the outlet orifice 2.

In the embodiment illustrated in FIG. 2, the blades 39 on the carrier 40 of the interior electrode 41, and the blades 33 of the exterior electrode 32 create a rotating annular stopper barring the gas in leaking from the chamber surrounding the electrode 41, through the gap existing between the insulating cylinder 35 and the block 55. From the ring, the liquid is carried away by the channels 51 and 52. The electric arc burns between the interior circumference of the electrode 32 and the annular interior electrode 41. The liquid is brought into the vortex movement through the conducts 54 and 48, and over the surfaces of the screens 36 and 38, and, having been directed by the projections 57 and 56, flows down into the liquid ring.

In both the embodiments, the plasma is generated from the liquid forming the walls of the vortex channel. Its composition might be broadly changed with regard to the technology to be followed, either in choice of the proper liquid, or in kind and quantity of the additional gas fed into the chamber surrounding the interior electrode 41.

The disc of the interior electrode 23, as shown in FIG. 1, may be set in rotating movement not only by mechanical coupling with the carrier 12 of the interior electrode, but also by help of its proper drive, or by a drive transmission between the exterior electrode and the carrier of the interior electrode 12. The liquid for refrigeration of the electrodes can be introduced through separate inlets. The choice of the electrodes polarity depends on their material and on the composition of the liquid and the additive gas applied.

The invention will find application in cases of surface heat-treatments of metallic constructions and installations carried out by deposition of ceramic, metallo-ceramic or metallic coatings having to resist to high heats amounting to 1500 C. and more, i.e. particularly in combustion turbines, and thermal energy installations in general. In course of the deposition, the gun according to the invention forms sufficiently high temperatures up to 25,000 C. The coating the gun is able to deposit, is then highly resistant to abrasion and to chemically aggressive media, because of being formed by oxide materials (A1 0 ZrO and the like), by carbide materials (carbides of tungsten, titanium, tantalum, boron, nitrides, borides etc., and their mixtures with metals, the s.c. cermets).

It is quite natural that the application of the gun according to the inventions is by far not limited to this manner of exploitation. It can be advantageously utilized for heating of materials, as eg for cutting of metals, for melting dissociation of minerals, i.e. wherever the material shall be affected by an intense thermal source having a high temperature gradient in the melting focus.

What is claimed is:

1. In a plasma-jet-gun, the combination of a housing having a channel for stabilizing the trunk of an electric arc and having passageway means for introducing plasma generating gas into said channel, an interior metallic electrode facing the inner end of said channel and an exterior electrode adjacent the outer end of said channel for establishing the electric arc in said channel, means for mounting said electrodes for rotation about an axis parallel to the axis of said channel, and drive means for rotating said electrodes, said housing and said electrodes having passageway means for circulating a liquid for cooling said housing and said electrodes.

2. In a plasma-jet-gun according to claim 1, wherein said electrodes are circular, said interior eletrode has a disc portion facing the inner end of said channel, and said exterior electrode has a cylindrical portion facing the axis of said channel and adjacently spaced therefrom.

3. In a plasma-jet-gun according to claim 2, wherein said cylindrical portion faces radially outwardly.

4. In a plasma-jet-gun according to claim 2, wherein said cylindrical portion faces radially inwardly.

5. In a plasma-jet-gun according to claim 1, wherein at least one of said electrodes has blades on the periphery thereof and said housing has passageway means for directing a portion of the liquid against said blades to provide said means for rotating said electrodes.

6. In a plasma-jet-gun according to claim 5, wherein both of said electrodes are provided with said blades.

7. In a plasma-jet-gun according to claim 1, wherein said housing has passageway means for establishing a shield of cooling liquid about the trunk of the electric are passing through said channel.

8. In a plasma-jet-gun according to claim 1, wherein said electrodes each have a commutating ring and a brush engages each of said rings for conducting electrical current to said electrodes.

References Cited by the Examiner UNITED STATES PATENTS 3,047,709 7/62 Browning 219-75 5 3,082,314 3/63 Arata et al. 219-75 3,097,292 7/ 63 Kugler et al. 219121 3,116,405 12/63 Browning et al. 219-75 RICHARD M. WOOD, Primary Examiner.

10 JOSEPH V. TRUHE, SR., Examiner.

Claims

1. IN A PLASMA-JET GUN, THE COMBINATION OF A HOUSING HAVING A CHANNEL FOR STABILIZING THE TRUNK OF AN ELECTRIC ARC AND HAVING PASSAGEWAY MEANS FOR INTRODUCING PLASMA GENERATING GAS INTO SAID CHANNEL, AN INTERIOR METALLIC ELECTRODE FACING THE INNER END OF SAID CHANNEL AND AN EXTERIOR ELECTRODE ADJACENT THE OUTER END OF SAID CHANNEL FOR ESTABLISHING THE ELECTRIC ARC IN SAID CHANNEL, MEANS FOR MOUNTING SAID ELECTRODES FOR ROTATION ABOUT AN AXIA PARALLEL TO THE AXIS OF SAID CHANNEL, AND DRIVE MEANS FOR ROTATING SAID ELECTRODES, SAID HOUSING AND SAID ELECTRODES HAVING PASSAGEWAY MEANS FOR CIRCULATING A LIQUID FOR COOLING SAID HOUSING AND SAID ELECTRODES.