US2768279A - Electric arc torch apparatus - Google Patents

Description

Oct. 2 3, 1956 A. RAVA ELECTRIC ARC TORCH APPARATUS 5 EheCts-Ehee' 1 Filed Jan. 18, 1955 @ATTO/anw',

Oct. 23, 1956 A. RVA

ELECTRIC ARC TORCH APPARATUS Filed Jan. 18|. 1955 5 Sheets-Ehem 2 Hwy@ ` Oct. 23, 1956` A RAVA 2,768,279

ELECTRIC ARC TORCH APPARATUS Filed Jan. 18, 1955 3 Sheets-Ehem 5 INVENTOR ALEXANDER RAVA .sf/@0% VM 6K5 TTORNEY United States Patent O ELECTRIC ARC TORCH APPARATUS Alexander Rava, deceased, late of Jersey City, N. J.; by William A. McDonald, administrator, Jersey City,

Application January 18, 1955, Serial No. 482,513

20 Claims. (Cl. 219--759 The present invention relates to the art including electric arc torches, and is more particularly concerned with the provision of features for permitting extended high temperature operation of such torches.

In the production of high temperatures for a variety of purposes, attention has long been directed to the electric arc produced by applying a proper voltage between a pair of electrodes to ionize the air or other gas therebetween, the consequent ilow of high values of current producing elevated temperatures in the gas. Such electric arcs have been utilized for welding, for fusing materials supplied to the arc, for accomplishing chemical processes under high temperature conditions, and the like.

However, in conventional systems utilizing Yelectric arcs, difficulty is experienced in the design and construction of suitable apparatus because of the necessity of providing means for supplying materials to be acted upon by the arc and for readily deriving from the are the materials previously acted upon by the arc. As a consequence, elaborate and complex mechanisms have been suggested and utilized for conveying powdered, gaseous or solid materials to the arc either internally of a hollow electrode and hence in an axial direction along the axis of the arc, or else transversely of the arc. Such methods may be suitable where the products formed by the arc are of a gaseous type which can be readily conducted away from the arc by exhaust Systems, or where the products acted upon by the arc can be readily moved out of the zone of interaction with the arc.

One particularly important use for high temperatures is in the vaporization or atomization of solid materials for the purpose of spraying them upon surfaces or backings to provide densely adherent coatings. A particularly important application of such methods is in the protection of conventional materials from the effects of high ternperatures which they may encounter in use; for example, in combustion engines or jet engines extremely high temperatures are encountered and are desired for increase in efficiency. Heretofore the temperatures utilizable in the operation of such devices have been severely limited by the materials of which these devices are made, since high temperature failure of the materials forms a limitation upon the efficiencies and etective lives of such devices. A highly desirable apparatus would be one which could coat conventional materials with refractory and temperature-resistant materials so as to provide a surface coating which can preserve such conventional materials against the effects of elevated temperatures at which they may be operated. Necessarily, the proper handling of such refractory materials requires extremely high temperatures.

The present invention provides means for accomplishing these and other desirable results in a convenient and simple form. According to one aspect of the present invention, an electric arc device is provided in which the arc is axially extended. That is, the arc extends beyond the space between the electrodes, such extension being along the axis of the electrodes, producing what may be termed an arc torch having a ilame with a temperature determined by the amount of electrical energy supplied thereto. The present invention further provides means for maintaining such an arc and for supplying to such arc materials to be vaporized therein and in such manner that these materials are projected along the axis of the arc, to be heated thereby, and then beyond the arc to impinge upon any material which it is desired to coat by such materials.

The present invention is further concerned with particular features of advantage in such a system for permitting its efficient operation under a wide variety of conditions of arc temperature and of coating material, providing a versatility of operation or operation with many types of material, refractory or otherwise, and under widely varying conditions of temperature.

These and other features and advantages of the present invention will become more fully apparent from consideration of the following description of a preferred embodiment thereof taken in conjunction with the appended drawings, in which:

Figure l shows an elevational View of one form of the invention;

Figure 2 shows a transverse cross-sectional view of the deviceof Figure l taken along line 2-2 thereof;

Figure 3 is a further transverse cross-sectional view of the device of Figure l taken along line 3 3 thereof;

Figure 4 is a longitudinal cross-sectional view of the device of Figure l taken at right angles thereto, illustrating its internal construction, and s howing the manner of its connection to the electrical equipment with which it forms the arc circuit; and

Figure 5 is a longitudinal cross-sectional view of a modification of the device of Figures l-4.

Referring to the drawings, the present device has three general sub-divisions, namely, an upper electrode portion 11, a column portion 12 and a lower electrode portion 13. The upper electrode portion 11 comprises a hollow annular conductive electrode 21 having an inwardly tapered bore portion 22 and an outwardly flaring bore portion 23. This electrode 21 is surrounded by a water jacket 24 having a water inlet pipe 26 and a water outlet pipe 27 supported on an insulating electrode holder plate 28.

The lower electrode portion comprises a solid conductive electrode 31 preferably formed of refractory material, such as tungsten, tantalurn, or the like, which is preferably a cylindrical, rectangular or polyhedral block. This electrode block 31 is supported in a heat-conductive electrode holder 32 joined to a hollow cylinder 33 forming the exterior jacket of a water-cooling arrangement. The electrode holder 32 and jacket cylinder 33 are mounted in an insulating outer sleeve 34a, 34's, secured thereto. Centrally located within the jacket cylinder' 33 is a pipe 36 connected at one end to the water inlet 37. Water outlet 38 communicates with the cylinder 33, whereby cooling water or other coolant may be supplied through inlet 37 and pipe 36 to the lower face of the electrode holder 32 to extract heat from the electrode 3l. Such heated water then flows to the water outlet 38 through the cylinder 33.

The lower electrode 31 and its supporting and cooling arrangement just described are surrounded by a gas inlet housing 39 having a cylindrical wall with a gas inlet pipe 41 communicating therewith. The housing 39 has insulating end walls 51, 52. The jacket sleeve 34a, 3417 is slidably mounted within a hub 52a of end wall 52` and is thereby axially adjustable relative to the housing 39 for a purpose to be described.

The column section 12 of the device extends between the upper electrode section 11 and the lower electrode section 13, being clamped therebetween. by the rods 42,

vcentric with the Iaxis of the device.

which may be of conductive or non-conductive material. This column section 12 comprises a pair of apertured spacer blocks 43 of insulating material and a single material-injection section 44. Each of these sections 43 and 44 has la bore 50 substantially equal in diameter to that of lthe inlet bore 53 of the annular electrode 21 and coaxially surrounding the lower electrode block 31. The material-injection section 44 is provided with a plurality (illustratively shown as three in number) of inlet pipes 46 communicating with the bore 50 of this section 44 at an angle nearly tangentially of the bore 51E, and also disposed at an acute angle to the axis of the bore 50. By way of illustration, in the transverse cross-sectional plane illustrated in Figure 2, these pipes may be at an angle of between 30 and 60 to the tangent of the bore 5t) and, in the axial longitudinal plane, as illustrated in Figure 4, they may be at an angle of between 30 and 60 to the axis of the bore 50. A water jacket 47 having a water inlet 48 and a water outlet 49 may be provided on the material-injection section 44.

As indicated in Figure 4, the jacket sleeve 34a for the lower electrode 31 has a tapered end portion 35. The gas chamber jacket 39 has a tapered aperture 40 in the end wall 51 therein substantially coaxial with the electrodes 21, 31 and with the jacket sleeve 34a. By adjustment of the electrode and jacket assembly 31, 32, 34a, 34b, in an axial direction, the gap 45 between the gas housing end plate 51 and the electrode jacket section 35 may be readily adjusted. In operation, a gas under suitable pressure is supplied to the gas inlet pipe 41. By virtue of the substantially tangential connection of the gas inlet pipe 41 to the gas chamber 39, and because of the inlet velocity of the gas entering the chamber 39, a swirling motion is imparted to the gas substantially con- This gas can escape from the gas chamber 39 only through the annular aperture 45, and accordingly has a substantially helical motion in its travel through the bore of the device to the upper electrode 21. Suitable pressures and velocities for the gas may range between and 50 pounds per square inch and 100 to 500 cubic feet per minute at the annular aperture. The particular gas utilized is one which should have high temperature stability and is preferably air or one of the inert gases, such as argon, nitrogen, or the like. Hydrogen can be used, similarly to its use in the atomic hydrogen torch.

In operation, an electrical difference of potential is applied between the electrode 21 and the electrode 31 by suitable connections 54, 55 to an electrical generator or source (not shown). The arc between the electrode is struck in any suitable manner. For example, a conductive rod may be inserted from the upper end through the bore 50 of the device to contact both the lower electrode 31 and the upper electrode 21. This conductive rod may thereupon be withdrawn. As it is slowly withdrawn, maintaining contact with the electrode 21, it strikes the arc between its end and lower electrode 31 and, as the striking rod is completely withdrawn, the arc extends between the electrode 31 and the electrode 21. The gas forced into the column through the annular aperture 45 surrounds the arc and tends to maintain it in a concentrated stream form. At the same time, this gas is heated, forming an easier path for the flow of ions. As this heated gas leaves the nozzle-like electrode 21 it blows the arc outwardly of the electrode 21 and, in fact, the arc assumes a configuration shown by the dash-dot lines 56, in which within the column portion 12 it is a narrow stream which as it leaves electrode 21 fans upwardly in all directions like a fountain, to fall back upon the outer surface of electrode 21. This outer portion of the arc at 56a is in effect a aming torch having high temperatures far in excess of those obtainable by those of conventional torches of combustible material, such as gases or the like, or even the atomic hydrogen torch, the

'effective heating of the materials.

tion and elevation of temperature.

temperatures being essentially determined by the electrical energy supplied to the arc.

While the torch thus far described may be utilized in conventional manner for soldering, brazing, welding, heat-treating, or other uses for conventional torches, the present invention provides further features whereby powdered or comminuted materials may be supplied to the arc itself to be heated therein to extremely high temperatures, which may approach or exceed the vaporization point of the material involved. Such materials are conducted along the axis of the torch through the nozzle electrode 21, into the extended flame of the torch and therebeyond, Where they may be usefully employed, as by spraying upon any objects which it is desired to coat. For this purpose the material to be sprayed is supplied to the pipes 46, preferably in the form of a powder carried by suitable inert gas under pressure. Because of the angle at which each of the pipes 46 is arranged with respect to the axis of the device, the powdered material is carried upward in the gure in spiral convolutions around, and becomes intimately mixed with, the arc within the column nozzle portion 12, the portion 21, and the flame portion 52 of the arc, to be appropriately heated thereby before exiting from the arc for useful purposes.

According to one feature of the present invention, the helical movement imparted to the gas-plus-powder injected through pipes 46 is in the same rotational sense as that of the gases introduced to the bore 50 through aperture 45, to avoid any disruption of the smooth concentrated are in bore 50 land to assist in the even distribution of material in the arc, resulting in a smooth and even vaporized spray extending beyond the arc portion 56a.

Another feature of the present invention resides in the conguration of the annular electrode 21; as shown, it

'has a tapered section 53 with narrowing bore in the vdirection of flow of the gas and materials, followed by a flared portion. This narrowed portion assures that the helically moving sheath of gas and materials7 after its passage along the bore 50 around and in the edges of the columnar arc, is intimately in Contact with the arc for Also the ared portion of the electrode 21 serves as a nozzle for the projection of the Vaporized or heated materials as a spray, and simultaneously provides a properly formed equi-potential surface to form the axially extended arc into a torch of desired shape. Y

The nozzle-like electrode 21 offers special advantage. As the stream of gas and material is carried upward along the arc, the inwardly tapering bore 22 serves to assure that the material has intimate contact with the higher temperature portions of the arc. Also, the slight buildup of pressure at the narrowest portion of the bore slows fdown the vaporized material slightly, assuring a longer 'association with the arc so as to attain more complete Ybeyond the outer arc ame toward the object being coated.

The swirling action of the gas and work material is also a feature of the invention in providing a longer path for the work, also assisting in complete vaporiza- The longer gas path serves to assist in cooling the inner walls of the column to avoid undue temperatures there.

As indicated above, lower electrode 31 and its jacket 34, 35 are adjustable vertically within hub 52a. This serves to adjust the radial width of annular gap 40, so ias to determine the volume and flow of gas in column 12.

Any desired clamping arrangement may be used to tix elements 31, 33, 34 in position, once adjusted.

It will be understood that suitable powdered or comminuted materials and gases may be supplied through the pipes 46 for chemical interaction between such materials and gases to provide chemical and/or physical changes in these materials, the materials after being acted upon being ejected through the nozzle 21 and beyond the arc torch portion 56a to be collected or utilized as desired.

In operation, the arc torch as shown in Figure 4 is connected by leads 54 and 55 to an electric power circuit comprising a resistor 57, a capacitor 58, and the secondary 59 of a high voltage power transformer 60. The resistor S7, capacitor 5S, and secondary 59 are connected in series, and the primary 61 of the high voltage transformer is connected to a suitable source of alternating current power.

For most eicient operation of the arc torch it is essential that the electrical components of the series circuit be properly chosen so that during the stable operation of the arc torch the power circuit in which the arc torch is connected will be in resonance. Resonance may be obtained when the relationship between the electrical components fulfills the two essential conditions herewith specified:

Let R be the electrical resistance in ohms of the resistor 57, which may include the internal resistance of secondary 59.

Let C be the capacitance in farads of the capacitor 58.

Let L be the inductance in henries of the high voltage transformer 60 as measured in the secondary 59 when the arc torch current is iiowing.

Let gf be the frequency in cycles per second of the alternating current source to which the primary 61 is connected- Then,

1. R2 must be less than JC-Ii As an illustration of the magnitudes of these components for an actual operating condition, the following values are given:

f=60 cycles per second R=4.60hII1S L=0.685 henries C=11.55 microfarads During this operation the following measurements were taken:

The arc current 20 amperes Voltage across the capacitor 58 4000 volts Voltage across the arc torch 800 volts Voltage across the transformer secondary 59 400 volts.

It has also been discovered that such a torch such as disclosed in Patent No. 2,059,276 or as described above may be used Very effectively for welding, having many advantages over other welding apparatus and methods already known.

In Fig. 5, the torch there illustrated has an inner electrode 7l and an outer electrode 72 surrounded by a water jacket 73. The inner electrode may have a central opening 74 as shown. The electrodes are mounted upon an insulating base 7S having a ring of insulating material 76 permitting them to be held rigidly together. The base 75 may have openings 77 therein as shown.

In using the torch for welding the work will be grounded as illustrated at 7S as will be electrode 72. An alternating or direct current of suitable high voltage may be applied between the electrodes 71 and 72 by means of the leads 79 and 70. The arc may be struck by a momentary metallic connection between the electrodes. After the arc is started, the torch may be brought into proximity with the work 78. The arc will then transfer itself from the electrode 72 to the work 78 and the welding operation may then be performed. Filler material may be supplied to the arc through the center opening 74 in the electrode 71 or, if desired, a suitable gas may be supplied to the arc through this electrode. A

suitable gas such as air, an inert gas, hydrogen, or any other' gas which may be desired may also be supplied through the openings 77 either by the draft created by the arc or under pressure as desired or required by the work to be done. All materials which may be supplied to the arc either through the opening 74 in the electrode 71 or through the openings 77 in the base 75 are included within the term arc material, as there is no concern here with the particular materials to be used but with the method involved. It is noted, however, that this det/ice and method may be used for example for atomic hydrogen welding by supplying hydrogen. Also it may be used as a shielded arc by supplying an inert gas. The welding material supplied through the opening 74 may be in powdered form or in the form of a wire or rod.

lt will be understood that the arc torch described with respect to Figs. l-4 may be used here in exactly the same manner as the torch of Fig. 5.

As stated above, the arc may be struck and the operation of the torch commenced independently of the work. The arc will then play out from the flared end of the inner electrode and return to the outer electrode but will transfer to the work upon being brought in proximity thereto, as the work will offer a shorter return path to ground available to the arc than will the outer electrode.

In use it will be noted that the torch may be used for preheating the work as the arc is not rigidly confined to a single spot.

This new method of welding has a number of advantages many of which will be understood from the foregoing description. It might be also mentioned that it may be used with relative ease for overhead Welding, with filler material supplied to the weld. The electrode 71 does not melt in use and, therefore, does not require frequent replacement. The arc is easy to direct and control, being directed and steadied by the draft of air surrounding the arc and directed toward the weld. When used for atomic hydrogen welding, it is economical of hydrogen, the gas being directed toward the weld, and therefore, more or less confined to the actual position where it is needed.

The above description is, of course, illustrative only, since other equivalents to its various features may be known, the actual invention being defined solely by the appended claims.

What is claimed is:

l. An axially extended electric arc torch comprising a first electrode block, a cylindrical gas chamber surrounding said electrode block, a gas inlet communicating with said chamber substantially tangentially thereof, a second electrode spaced axially from said first electrode block, said second electrode having an axial bore converging away from said first electrode block and also having a flaring bore outer portion, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, said chamber having an aperture in register with said spacer bores and surrounding said first electrode with an annular gap therebetween, said column also including a single hollow material-injection section aligned with and between said spacer sections, clamping means for retaining said chamber, column and second electrode in axial alignment, and a plurality of material-injecting inlets formed in said injection section and including a plurality of pipes disposed at an acute angle to the axis of said device in both longitudinal and transverse planes, each of said pipes being at an angle of between 30 and 60 to the radius of said column in a transverse plane and at an angle of between 30 and 60 to the axis of said column in a longitudinal plane.

2. An axially extended electric arc torch comprising a first electrode block, a cylindrical gas chamber surrounding said electrode block, a gas inlet communicating with said chamber substantially tangentially thereof, a second electrode spaced axially from said rst electrode block, said second electrode having an axial bore converging away from said first electrode block and also having a aring bore outer portion, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, said chamber having an aperture in register with said spacer bores and surrounding said first electrode with an annular gap therebetween, said column also including a single hollow material-injection section aligned with said spacer sections, clamping means for retaining said chamber, column and second electrode in axial alignment, and a plurality of material-injecting inlets formed in said injection section and including a plurality of pipes disposed at an acute angle to the axis of said device in both longitudinal and transverse planes.

3. An axially extended electric arc torch comprising a first electrode block, a cylindrical gas chamber surrounding said electrode block, a gas inlet communicating with said chamber, a second electrode spaced axially from said first electrode block, said second electrode having an axial bore converging away from said first electrode block and also having a flaring bore outer portion, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, said chamber having an aperture in register with said spacer bores and surrounding said first electrode with an annular gap therebetween, said column also including a single hollow material-injection section aligned with and between said spacer sections, clamping means for retaining said chamber, column and second electrode in axial alignment, and a plurality of material-injecting inlets formed in said injection section and including a plurality of pipes disposed at an acute angle to the axis of said device in both longitudinal and transverse planes.

4, An axially extended electric arc torch comprising a first electrode block, a cylindrical gas chamber surrounding said electrode block, a gas inlet communicating with said chamber, a second electrode spaced axially from said iirst electrode block, said second electrode having an axial bore, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, said chamber having an aperture in register with said spacer bores and surrounding said first electrode with an annular gap therebetween, said column also including a hollow material-injection section aligned with said spacer sections, clamping means for retaining said chamber, column and second electrode in axial alignment, and a plurality of material-injecting inlets formed in said injection section and including a plurality of pipes disposed at an acute angle to the axis of said device in both longitudinal and transverse planes.

5. An axially extended electric arc torch comprising a Iirst electrode, a gas inlet chamber surrounding said first electrode, a gas inlet communicating with said chamber, a second electrode spaced axially from said iirst electrode, said second electrode having an axial bore and also having a flaring bore outer portion, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, said chamber having an aperture in register with said spacer bores and surrounding said first electrode with an annuiar gap therebetween, said column also including a hollow material-injection section, clamping means for retaining said chamber, column and second electrode in axial alignment, and a plurality of materialinjecting inlets formed in said injection section and including a plurality of pipes disposed at an acute angle to the axis of said device in both longitudinal and transverse planes.

6. An axially extended electric arc torch comprising a first electrode, a gas inlet chamber surrounding said rst electrode, a second electrode spaced axially from Said first electrode, said second electrode having an axial bore and also having a aring bore outer portion, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, said chamber having an aperture in register with said spacer bores and surrounding said first electrode with an annular gap therebetween, means for supplying gas under pressure to said chamber with a swirling movement about the axis of said column to pass through said annular gap into said column bore with said swirling movement, said column also including a hollow material-injection section, clamping means for retaining said chamber, column and second electrode in axial alignment, and means in said material-injection section for injecting material to be acted upon into said column bore and with a swirling movement in the same sense as said gas swirling movement.

7. An axially extended electric arc torch comprising a first electrode, a second electrode spaced axially from said first electrode, said second electrode having an axial bore, a hollow column spacing said electrodes, and comprising a plurality of insulating spacer sections, each having a bore extending axially of said electrodes, means for passing inert gas through said column bore with a swirling movement about the axis of said column, said column also including a hollow material-injection section, clamping means for retaining said chamber, column and second electrode in axial alignment, and means in said material-injection section for injecting material to be acted upon into said column bore and with a swirling movement in the same sense as said gas swirling movement.

8. An axially extended electric arc torch comprising a first electrode, a second electrode spaced axially from said first electrode, said second electrode having an axial bore, a hollow column longitudinally spacing and in insulated relation with said electrodes, and having a bore, means for passing inert gas through said column bore with a swirling movement about the axis of said column, means for retaining said electrodes and column in axial alignment, and means for injecting material to be acted upon into said column bore at a point between said electrodes and with a swirling movement in the same sense as said gas swirling movement.

9. An axially extended electric arc torch comprising a irst electrode, a second electrode spaced axially from said first electrode, said second electrode having an axial bore, a hollow column spacing said electrodes, and having a bore, means for retaining said electrodes and column in axial alignment, means for passing inert gas through said column bore with a swirling movement about the axis of said column, and means for injecting material to be acted upon into said column bore at a point longitudinally between said electrodes,

10. An axially extended electric arc torch comprising a lirst electrode, a second electrode spaced axially from said first electrode, said second electrode having an axial bore, a hollow column spacing said electrodes and having a bore, clamping means for retaining said electrodes and column in axial alignment, means for passing inert gas through said column bore in the direction of ow through said second electrode, whereby said iirst electrode may be termed the upstream electrode and the second electrode may be termed the downstream electrode, and means for injecting material to be acted upon into said column bore at a point downstream from said upstream electrode.

ll. An axially extended electric arc torch comprising a tirst electrode, a second electrode spaced axially from said iirst electrode in its entirety, said second electrode having an axial bore, a hollow column separatingrsaid electrodes and having a bore in alignment with said electrode bore, means for passing inert gas around said rst electrode into said hollow column and helically along the bore thereof and along said second electrode bore, and means for injecting material to be acted upon by said arc into said column bore at a point between said electrodes and with a helical motion along the axis of said column bore, whereby said arc is extended between said electrodes and beyond said second electrode and said material passes along said arc axially through and beyond said second electrode.

12. An axially extended electric arc torch comprising a first electrode, a second electrode spaced axially from said first electrode, said second electrode having an axial bore, a hollow insulating column separating said electrodes and having a bore in alignment with said electrode bore, means for passing inert gas around said first electrode into said hollow column and helically along the bore thereof and along said second electrode bore, and means for injecting material to be acted upon into said column bore at a point between said electrodes and with a swirling motion advancing said material helically along said column bore.

13. An axially extended electric arc torch comprising a first electrode, a second electrode having a bore and axially spaced from said first electrode, a hollow column longitudinally entirely separating said electrodes and having a bore in alignment with said first bore, a housing surrounding said first electrode with an annular gap therebetween, and means injecting gas under pressure into said housing substantially tangentially thereof and in a plane perpendicular to said bore axis.

14. An axially extended electric arc torch as lin claim 13, wherein said first electrode is supported on a tapered support, `and including means for axially adjusting said support relative to said housing to adjust the width of said annular gap.

15. An axially extended electric arc torch comprising la first electrode, a second electrode having a bore and entirely axially spaced from said first electrode, :a hollow column separating said electrodes and having a bore in alignment with said first bore, and means for injecting material to be acted upon into said column lbore at Ia point between and spaced from both said electrodes and with a swirling motion advancing said material helically along said column bore.

16. An axially extended electric arc torch comprising a first electrode, -a |second electrode Ihaving =a bore and axially spaced from `said first electrode, a hollow insulating column longitudinally separating said electrodes and having a bore in alignment with said first bore, lthe bore of said second electrode converging away from said first electrode and having `an outer flared portion, and means for passing gas along said column bore outwardly of said bored electrode to produce fan axially extended arc.

17. An axially extended electric arc torch, comprising a first electrode, a second electrode having a bore and axially spaced from said first electrode, a hollow column separating said electrodes and having `a bore in alignment with said first bore, a high voltage power transformer having a primary ywinding adapted to `be coupled to a source of alternating current and also having a secondary winding, a capacitor, a resistor, said secondary winding, capacitor and resistor :being connected to said electrodes in a series circuit, said circuit being resonant at the frequency of said source Iduring the existence of said arc.

18. An axially extended electric-arc torch, comprising a first electrode, a second electrode having a bore and axially spaced from said first electrode, -a hollow insulating column longitudinally entirely separating said electrodes and Ehaving a bore in alignment with said first bore, and electric-excitation means connected to said electrodes and including means electrically yresonant with said torch `during the existence of an arc between said electrodes.

19. ln an electric-arc torch, spaced electrodes including a hollow electrode having a bore on an arc axis extending from one of said electrodes to said hollow electrode, pressurized-gas supply mea-ns including means developing an arc-confining swirl helical about and along said axis, Iand electric-excitation means connected to said electrodes and including means resonant with Isaid torch during existence of an arc confined by said swirl.

20. In an electric-arc torch, an arc chamber comprising a plurality of interfitting hollow sectional elements defining an elongated passage, said sectional elements including at the downstream end thereof an element of conductive material defining a downstream electrode, the element adjacent said downstream electrode being of insulating material, an upstream electrode positioned coaxially with respect to an upper sectional element of said `arc chamber, and means for inducing a flow of gas along said chamber and through said downstream electrode.

References Cited in the file of this patent UNITED STATES PATENTS 1,002,721 Mathers Sept. 5, 1911 1,616,145 Shipman Feb. 1, 1927 1,638,336 Hines Aug. 9, 1927 2,003,167 Alexander May 28, 1935 2,052,796 Rava Sept. 1, 1936 2,308,510 Herman Ian. 19, 1943 FOREIGN PATENTS 664,523 Germany Aug. 30, 1938

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