US3740522A

US3740522A - Plasma torch, and electrode means therefor

Info

Publication number: US3740522A
Application number: US00133126A
Authority: US
Inventors: E Muehlberger
Original assignee: Geotel Inc
Current assignee: Geotel Inc
Priority date: 1971-04-12
Filing date: 1971-04-12
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19

Abstract

The torch comprises an insulating housing in which are mounted a metallic front housing and a metallic rear housing. Five coaxial metal tubes are provided in radially-spaced relationship to define four annuli and a central passage. The two inner tubes extend from the rear housing to the cathode holder to deliver electricity and cooling water thereto. The two outer tubes extend from the front housing to the anode for conduction of electricity and cooling water thereto. The intermediate tube extends from the insulating housing to the anode and cooperates with a fluted gasinjector and spacer sleeve to pass arc gas to the arc chamber. An external tube conducts spray powder to the anode. The anode has alternating water-in and water-out longitudinal passages which efficiently cool it and permit a very small diameter in relation to power capabilities. The anode is removable and may be straight-flow, angular-flow, and/or supersonic. The outermost tube is removably secured in a clamping and current-conducting portion of the front housing. The cooling water flows in series, and in four directions, through the central passage and inner annulus, through the outer two annuli, and also through the housings. All of the tubes are removable and may be long or short, thus adapting the torch for spray coating the interiors of various lengths of pipe. External protuberances on various tubes maintain concentricity regardless of tube length.

Description

United States Patent [1 1 Muehlberger June 19, 1973 I PLASMA TORCH, AND ELECTRODE MEANS THEREFOR Erich Muehlberger, Costa Mesa, Calif.

22 Filed: Apr.12, 1971 21 App]. No.: 133,126

[75] Inventor:

[52] U.S. Cl 219/121 P, 219/75 [51] Int. Cl B23k 9/00 [58] Field of Search 219/76, 121 P, 74,

[56] References Cited UNITED STATES PATENTS 3,130,292 4/1964 Gage et al. 219/121 P X 2,768,280 10/1956 Renaudie 219/75 X 3,242,305 3/1966 Kane et a] 219/75 3,145,287 8/1964 Siebein et al. 219/75 3,179,784 4/1965 .Iohnson 219/76 FOREIGN PATENTS OR APPLICATIONS 1,151,092 5/1969 Great Britain 219/121 P Primary Examiner.1. V. Truhe Assistant ExaminerGale R. Peterson AttorneyGausewitz, Carr & Rothenberg [57] ABSTRACT The torch comprises an insulating housing in which are mounted a metallic front housing and a metallic rear housing. Five coaxial metal tubes are provided in radially-spaced relationship to define four annuli and a central passage. The two inner tubes extend from the rear housing to the cathode holder to deliver electricity and cooling water thereto. The two outer tubes extend from the front housing to the anode for conduction of electricity and cooling water thereto. The intermediate tube extends from the insulating housing to the anode and cooperates with a fluted gasinjector and spacer sleeve to pass arc gas to the arc chamber. An external tube conducts spray powder to the anode.

The anode has alternating water-in and water-out longitudinal passages which efficiently cool it and permit a very small diameter in relation to power capabilities. The anode is removable and may be straight-flow, angular-flow, and/or supersonic. The outermost tube is removably secured in a clamping and current-conducting portion of the front housing. The cooling water flows in series, and in four directions, through the central passage and inner annulus, through the outer two annuli, and also through the housings. All of the tubes are removable and may be long or short, thus adapting the torch for spray coating the interiors of various lengths of pipe. External protuberances on various tubes maintain concentricity regardless of tube length.

18 Claims, 17 Drawing Figures Patented June 19, 1973 6 Sheets-Sheet l INVENTOR.

MQQM mm wq um mun m vxmk 1 Patented June 19, 1973 3,740,522

6 Sheets-Sheet 2 INVENTOR.

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Patented June 19, 1973 6 Sheets-Sheet 5 Patented June 19, 1973 3,740,522

6 Sheets-Sheet 4 INVENTOR. [IF/(H MUEHA BfFGE/Q Patented June 19, 1973 6 Sheets-Sheet 5 INVENTOR- P/CI MZ/E 141.55 @615 1? BY 1 M ATTO/P/VEVS'.

PLASMA TORCH, AND ELECTRODE MEANS THEREFOR BACKGROUND OF THE INVENTION:

1. Field of the Invention This invention relates to the field of electrical plasma-jet torches wherein an electric arc is employed to heat the gas to a high temperature for purposes including, among others, spraying of various substances onto workpieces to coat the latter.

2. Description of Prior Art The electrical plasma-jet torch, as employed for spraying and other purposes, has been used to a considerable extent in the United States since the late 1950s. There are relatively large numbers of patents for numerous types of plasma spray torches. However, torches marketed prior to the present one are characterized by one or more of the following, and other, disadvantages:

1. They have large outer diameters and are heavy, cumbersome, etc. More specifically, they are unable to effect coating of the interiors of small-diameter pipes (for example, those having an inner diameter of only a little more than an inch).

2. They do not permit application of sufficiently high electrical power, in a very small space, to permit highspeed spray coating and other operations in severely confined regions.

3. Some commercial types do not water-cool the cathodes, so that cathode life is adversely affected.

4. The cooling of the anodes is not sufficiently efficient, which reduces anode life and necessitates employing anodes having large diameters.

5. The torch designs may not be quickly and economically modified in order to provide various desired types of highly uniform gas flows. Furthermore, the torch designs may not be quickly and economically modified in order to permit various desired toreh lengths from a small number of inches to many feet the latter being required when relatively long pipes are to be interiorly spray coated.

6. The anodes and/or cathodes may not be rapidly and easily replaced when desired.

7. The torches are excessively expensive, and are insufficiently rugged, rigid, etc.

Some prior-art plasma torches are described in the following -U.S. Pat. Nos.: 2,890,322; 2,922,869; 2,960,594; 3,030,490; 3,071,678; 3,114,826; 3,118,046; 3,145,287; 3,179,782; 3,179,784; 3,183,337; 3,194,941; 3,238,349; 3,246,114; 3,272,958; 3,301,995; 3,304,402; 3,307,011;

SUMMARY OF THE INVENTION The present invention solves the above and other problems by providing a substantial number of concentric tubes which may be any desired lengths, and by removably connecting such tubes to the electrodes and to front, rear and insulating housings. The small-diameter anode nozzle has numerous longitudinal bores some of which connect with the outer annulus between the two outermost tubes, and others of which connect with the annulus which is inwardly adjacent such outer annulus, the relationships being such that the anode may be operated for long periods of time at very high power. Several types of straight-flow and angular-flow anodes are provided and are bored for water cooling as indicated.

The outer tube not only conducts water and electricity but also is a removable connector which is secured by a current-conducting clamp assembly to the front housing. Gas is passed to the arc chamber through an annulus and through flutes and bores in a temperatureresisting sleeve, such sleeve operating as a spacer, an insulator, and as an economical gas-injector element which may be very small yet which facilitates creation of numerous types of gas flows. An efficient and compact circuit is provided to pass cooling water in series for cooling of both the anode and the cathode, the water flowing not only through such elements and through various tubes but also through the housings. The rear housing and the two inner tubes form an assembly which extends to a cathode holder for the removable cathode. Suchcathode is indented inwardly from injector ports in the sleeve, whereby gas flows uniformly and efficiently around the cathode to the arc chamber or passage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view illustrating a plasma torch constructed in accordance with the present invention and adapted to be hand-held by an operator;

FIG. 2 is an isometric view showing the exterior of the torch of FIG. 1;

FIG. 3 is an enlarged transverse sectional view taken on line 3-3 of FIG. 5a;

FIG. 4 is an enlarged transverse sectional view taken on line 44 of FIG. 5b;

FIGS. 5a and 5b are adapted to be joined together (in slightly overlapped manner) to form a greatly enlarged vertical sectional view of the major portions of the torch of FIG. 1;

FIG. 6 is a transverse sectional view on line 6-6 of FIG. 512;

FIG. 6a is a transverse sectional view on line 6a-6a of FIG. 5b;

FIG. 6b is a fragmentary longitudinal sectional view taken on line 6b-6b of FIG. 6;

FIG. 60 is a fragmentary longitudinal sectional view taken on line 6c-6c of FIG. 6;

FIG. 7 is an isometric view showing the front housing and the clamping neck projecting forwardly therefrom;

FIG. 8 is a vertical sectional view illustrating the forward portions of an elongated form of the present torch, wherein a 45 nozzle is provided and is mounted within a tube for spray-coating of the interior thereof;

FIG. 9 is a view corresponding to the left portion of FIG. 5b but showing a nozzle;

FIG. 10 is a view corresponding to the left portion of FIG. 5b but showing a supersonic nozzle;

FIG. 11 corresponds generally to FIG. 9, but shows a modified form of 90 electrode wherein means are provided to support the torch from both ends of the pipe being interiorly coated, the cooling means for the anode being unshown;

FIG. 12 is a view showing the torch as employed in coating the interior of a pipe, and illustrating in schematic form the rotating and feeding means for the pipe being coated, and the support means for the torch; and

FIG. 13 is an isometric view of the gas-injector sleeve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout this specification and claims, it is assumed that the rear or stick electrode is the cathode, and that the front or nozzle electrode is the anode. It is to be understood, however, that operation of the torch with the opposite polarity of connection, or with alternating or other type of current, does not avoid the appended claims.

FIG. 1 presents an overall view of the torch and is generally illustrative of a typical size of the torch. Thus, it is to be understood that the external diameter of the outermost one of the concentric tubes may be, for example, O.8l2 inch. This does not include the powderfeed tube. Because of the very small sizes of the parts, as shown in FIG. 1, the reference numerals will be applied primarily to the much larger views 5a and 5b.

Proceeding first to a description of what may be termed the cathode assembly, namely the rear electrode assembly, this comprises a rear housing (FIG. 5a) which may be formed of copper. The housing has a tubular body and a radial flange 11.

Soldered coaxially in a counterbore in the body of housing 10, and communicating with the central passage of such housing, is a central tube 12 which may be formed of stainless steel. A larger tube, numbered 13, and which may be formed of copper, is soldered in a much larger counterbore in housing 10 to thus define an annulus 14 between the two tubes 12 and 13. The portion of tube 13 which is not inserted into housing 10 is surrounded by an insulating sleeve 16. Such sleeve may be, for example, a type of polyvinyl chloride which shrinks when heat is applied thereto, the sleeve being heat-shrunk on the tube 13. Sleeve 16 insures that there will be no internal arcing between tube 13 and the tube radially-outwardly therefrom.

The front end of central tube 12 is soldered into a bore in a generally cylindrical cathode holder 17 (FIG. 5b) which may be formed of copper. Similarly, the larger tube 13 is soldered to holder 17 at a region spaced outwardly from tube 12, there being a neck 18 formed coaxially on the cathode holder and extending between the two tubes 12 and 13. The front end of the cathode holder 17 is bored and tapped to receive the threaded shank 19 of a cathode means 20. Such means comprises a cylindrical base element 21 having the shank 19 thereon and which may be formed of copper, and a thoriated tungsten slug 22 which is soldered coaxially in a bore in the base 21. Slug 22 is cylindrical and has a main body the diameter of which is somewhat smaller than that of the cylindrical outer surface of base 21. The front end of the tungsten slug is generally frustoconical and terminates in a rounded tip 23.

The main body of cathode holder 17 has a cylindrical exterior surface which is flush with the cylindrical exterior surface of base 21 of cathode means 20. At its rear end, the cathode holder 17 has a radial flange portion 25 the external cylindrical surface of which is flush with the external cylindrical surface of insulating sleeve 16.

The described elements comprise a unitary cathode assembly which may be inserted forwardly into the plasma torch through a generally cylindrical insulating housing 26 which is formed of a suitable insulating material such as nylon. More specifically, the tubular elements (including insulating sleeve 16) extend through an axial bore 27 in housing 26, whereas the tubular body of rear housing 10 seats snugly in a counterbore 28 in such insulating housing. The radial flange 11 of the rear housing seats in an additional counterbore and is locked in place by screws 29 which are threaded into inserts 31 in the insulating housing. The cathode assembly further comprises a fitting 32 which is soldered c0- axially to rear housing 10 and is adapted to be connected to a conductor of both water and electricity.

The cathode means 20 is a subassembly which is screwed into the cathode holder 17 after the abovedescribed cathode assembly is withdrawn through insulating housing 26 (or, alternatively, after the exterior portions of the forward region of the torch are removed). It is thus a simple matter to remove the means 20 and replace it with a new one when the tungsten slug 22 becomes excessively worn. It is a feature of the invention, however, that the electrode life is very long because of the design of the torch and because of the cooling of the cathode as described hereinafter.

DESCRIPTION OF THE REMAINING THREE CONCENTRIC TUBES, AND OF THE FRONT HOUSING In addition to the two concentric (coaxial) inner tubes 12 and 13 described above, there are three other concentric (coaxial) tubes of larger diameter and which are respectively numbered 33-35.

Tubes

33 and 34 may be termed the outer tubes, whereas tube 35 may be termed the intermediate tube since it is between the outer tubes 33-34 and the inner tubes 12-13. Tube 34 is the intermediate one of the three tubes 33-35, whereas tube 35 is the inner one of such three tubes.

Tube 35 may be formed of brass, and has a diameter much larger than that of insulating sleeve 16 whereby to define an annulus 36 between tube 35 and sleeve 16. The rear end of tube 35 extends into a counterbore 37 (FIG. 5a) in insulating housing 26, such counterbore being made from the left side of the housing (that is to say, forwardly of bore 27).

Tube 34, which may be formed of stainless steel, has a diameter larger than that of tube 35 to thereby define an annulus 38 therebetween. The outermost or exterior tube, numbered 33, may be formed of copper and has a diameter substantially larger than that of tube 34 whereby to define an additional annulus, numbered 39. As shown in FIG. 5b, the exterior tube 33 extends forwardly farther than does tube 34, which in turn extends forwardly farther than does tube 35. The three tubes 33-35 are associated with the anode as described below.

Referring particularly to FIG. 5a, the rear ends of the various tubes 33-35 are staggered generally correspondingly to the staggering or offsetting of the front ends thereof. Thus, tube 34 extends rearwardly farther than does tube 33, whereas tube 35 extends rearwardly farther than does tube 34.

The two outer tubes, 33 and 34, extend into a metallic (for example, brass) front housing 41 which has a generally tubular large-diameter body and also has a radial flange 42. Front housing 41 is seated snugly in a counterbore in the front side of insulating housing 26, being held in position by screws 43 which extend through flange 42 into inserts 44 in the insulating hous- The tube 34 extends to the right (rear) portion of front housing 41 and is seated in the counterbore therein. Tube 33 extends only to the left (forward) portion of the front housing, radially-inwardly from flange 42, being likewise seated in the counterbore in the front housing. The right or inner end of the front housing is open in order that the tube 35 (and the tubes 12 and 13) may pass therethrough.

USE OF THE CONCENTRIC TUBES IN TORCHES OF GREATLY VARYING LENGTHS, AND MEANS FOR MAINTAINING TUBE CONCENTRICITY The described type of concentric or coaxial relationship of the various tubes permits the forward regions of the torch to be very different in length without changing to an excessive degree the cost of manufacture. Thus, for example, FIGS. 1, 2 and 5 show a short version of the torch and which may be hand-held for spraying-of numerous surfaces, or for use in arc welding, are cutting, etc. Conversely, FIG. 12 shows one of numerous much longer versions of the torch. Whether the torch is only a few inches or hundreds of inches long, all parts other than the tubes remain the same. It is an important feature that different tube lengths may be substituted relative to the same housings and electrodes, in a short period of time.

To maintain the concentricity of the various tubes, in order that the water-flow and gas-flow paths will be uniform in cross'sectional sizes as is desired, circumferentially-spaced protuberances are provided on various ones of the tubes. protuberances are provided exteriorly on the innermost tube 12 and are numbered 46. The radial dimension of such protuberances 46 is selected to correspond to the desired radial dimension of the innermost annulus 14,

whereby the protuberances 46 touch the interior surface of tube 13 and maintain concentricity as desired. The protuberances 46 are provided at intervals along the length of the torch when a torch a number of feet in length is employed.

Referring next to FIG. 5b, exterior protuberances 47 are provided on tube 35. Such protuberances are dimensioned to project through the annulus 38 and touch the interior surface of tube 34, thus maintaining concentricity. In a similar manner, exterior protuberances 48 are provided on the exterior surface of tube 34 in order to engage the interior surface of tube 33.

The protuberances may be formed by building up solder on exterior surfaces of the various tubes. Alternatively, the interior surfaces of the tubes may be dimpled by predetermined amounts in order to form corresponding protuberances on the exterior surfaces thereof.

THE ANODE, AND THE MEANS TO MECHANICALLY AND ELECTRICALLY CONNECT IT TO FRONT HOUSING 41 Referring to FIG. 5b, the anode nozzle is numbered 49 and comprises a thick-walled metallic tube formed of copper or the like and having a cylindrical passage 50 extending axially therethrough. Such passage 50 comprises the arc passage, or are chamber, and contains the tip portion 23 of cathode slug 22. The diameter of the arc passage 50 corresponds generally to the outer diameter of slug 22 at the cylindrical body thereof. At its end adjacent the cathode, the arc passage 50 diverges rearwardly at a frustoconical wall portion 51 which is disposed radially-outwardly from the rear region of the frustoconical wall of tungsten slug 22.

The frustoconical wall portion 51 merges, at its rear end, with a cylindrical wall 52 which is disposed radially-outwardly from the forward region of the cylindrical Referring to FIGS. 5a-5b,

wall of slug 22. The diameter of such wall 52 is only slightly larger than the outer diameter of the cylindrical base 21 of cathode means 20.

Exceptfor the described are passage or chamber 50, and except for water-cooling and powder-injection passages described below, the anode 49 is formed of solid metal. Except for a closure ring described below, the anode is made of a single piece of copper.

It is emphasized that the diameter of arc passage 50 forwardly of tip 23 is unusually large in comparison to the overall diameter of the anode. Thus, in the illustrated form the diameter of the arc passage is substantially more than one-third of the diameter of the anode 49. It is further emphasized that the anode has substantially the same diameter as does the exterior tube 33 and that, except for the powder-feed tube described below, this is the outer diameter of the forward or working portion of the torch. The result is that the power capability of the torch is very high in comparison to the diameter thereof. Thus, in spite of the fact that the torch will coat a pipe interior surface which is only a little more than an inch in diameter, the power capabilities of the torch are very high. For example, the torch may operate for long periods of time at a power range between 40 and 50 kilowatts.

A major portion of the anode 49 is inserted coaxially into the outermost tube 33, the relationship being such that the exterior surface of tube 33 is substantially flush with the exterior cylindrical surface of the forward end of the anode. The anode is removably secured to the tube 33 by a threaded connection at 53. Thus, the outermost tube 33 provides a mechanical connection to the front housing 41 as well as providing a means to conduct current from the front housing to the anode.

The means for mechanically and electrically connecting the rear end portion of tube 33 to front housing 41 is a feature of the invention. Such means comprises a neck 54 formed coaxially of the body of front housing 41, forwardly of flange 42, and having an interior cylindrical surface which fits snugly around (in flatwise engagement with) the exterior surface of tube 33. As best shown in FIG. 7, the neck 54 is split or notched at circumferentially-spaced regions therearound and in a direction longitudinal to the front housing 41. Not only is the neck 54 split, but the wall of the neck is sufficiently thin that the sections between the splits may be flexed inwardly by an exterior clamp ring 57 which is threadedly connected to the neck 54 at connection 58. At its forward end, the clamp ring 57 has a radiallyinwardly extending flange 59 the interior surface 61 of which is forwardly convergent to correspond to a forwardly convergent beveled or frustoconical surface 62 formed exteriorly at the forward end of the neck.

In assembling the torch, an exterior tube 33 of a desired length is inserted into the neck 54, following which a spanner wrench (which is inserted in holes 63) is employed to turn clamp ring 57 and thereby cam the interior flange surface 61 up surface 62, thus flexing the neck sections between splits 56 until such sections are forced tightly against the exterior surface of tube 33. Thus, tube 33 is not only mechanically locked in the front housing 41, but is electrically associated with such front housing in a manner which minimizes contact. resistance and thus maximizes transmission of the very high currents which are passed forwardly to anode 49.

To conduct spray powder to the are passage or chamber 50, in order that the spray powder will be melted and entrained in the heated gas for transmission to a workpiece and consequent spray-coating thereof, the anode 49 is provided with a radial bore 64. Bore 64, in turn, communicates with an L-shaped passage 66 in a block 65 which is secured exteriorly to anode 49, on a flat portion thereof, by means of a screw 67. A powder tube 68, for example formed of stainless steel, communicates with the L-shaped passage 66 in block 65, being soldered to the block. Tube 68 extends parallel to and adjacent the outer tube 33 throughout a major portion of the distance between anode 49 and the front housing 41.

At a region relatively adjacent the front housing 41, tube 68 bends upwardly at an incline and at such an angle that the tube will pass radially-outwardly of the flange 42 on the front housing. Radially adjacent such flange, the powder tube 68 is bent parallel to the tube 33 and passes along insulating housing 26 to the rear of the torch where a fitting 69 is provided. Such fitting is connected to a suitable source of powder entrained in gas. One such source is described in US. Pat. No. 3,517,861, issued June 30, 1970, inventor Robert P. DeLaVega.

The region of the powder tube 68 forwardly of the inclined portion thereof may vary greatly in length. Thus, for example, the portion shown in FIG. 12 may be a number of feet in length and may be maintained closely adjacent tube 33 as by snap-on spring clips 70. The region of tube 68 which extends along housing 26 is held in position by a handle means described below.

WATER-COOLING MEANS FOR THE ANODE, AND COOLING CIRCUIT FOR THE ENTIRE TORCH Referring particularly to FIG. b, there will next be described the cooling passages in the solid copper anode 49. The solid anode is to be distinguished from numerous prior-art anodes wherein removable inserts were provided, and wherein O-rings or other seals were provided to maintain the integrity of cooling chambers around the removable inserts.

The portion of the anode 49 immediately rearward of the threaded connection 53 is reduced in diameter (necked down) to form a cylindrical surface 71 the diameter of which is the same as the outer diameter of tube 34. Tube 34 is abutted against a shoulder 72 rearwardly adjacent the reduced-diameter cylindrical portion 71. Thus, the outermost annulus 39 extends forwardly to the cylindrical surface 71.

In similar manner, the portion of the anode 49 rearwardly adjacent the forward end of tube 34 is reduced in diameter (necked down) to form another cylindrical surface 73 the diameter of which corresponds to the outer diameter of tube 35. The forward end of tube 35 is abutted against a shoulder 73b formed rearwardly adjacent cylindrical surface 73. Thus, the annulus 38 is extended to the surface 73.

As best shown in FIG. 6, a substantial number of bores (for example, twelve in the present illustration) are formed longitudinally of anode 49 in outwardlyspaced relationship from the wall of arc passage 50, and at all side regions of the torch except at the powder port or passage 64. One group of such bores may be referred to as water-in bores, whereas the remaining group of bores may be referred to as water-out bores. The water-in bores are numbered 74 and the water-out bores are numbered 75.

All of the

bores

74 and 75 are drilled in anode 49 from the forward surface thereof, and all extend rearwardly for at least the full length of the arc passage (forwardly of cathode tip 23). Formed in the forward face of anode 49 is an annular groove 76 which is, however, interrupted at the torch region forwardly of powder port 64 and screw 67. Groove 76 communicates with the forward ends of all of the

bores

74 and 75, and is closed by means of a closure ring 77 which is soldered in a groove formed in the forward face of the anode.

As shown at the lower portion of the left end of FIG. 5b, the rear ends of water-in bores 74 respectively communicate with radial bores 78 which extend to the above-described cylindrical surface 71. The water-out bores 75 respectively communicate with passages 79 which are drilled forwardly at an angle (FIG. from the cylindrical surface 73.

Accordingly, water flowing forwardly through annulus 39 passes through radial passages 78 to water-in bores 74, thence enters the interrupted annular groove 76, thence enters the water-out passages and passes through passages 79 to annulus 38 for rearward flow through the torch.

As shown in FIG. 6, the water-in and water-out bores generally alternate with each other, so that water is flowing in opposite directions (in most instances) through circumferentially adjacent passages. Because the water-in and water-out bores are in alternation, the crosssectional size of interrupted groove 76 may be made small. Thus, water from the lowermost bores 74, shown in FIG. 6, immediately passes out the bores 75 adjacent thereto. The groove 76 therefore, at its regions adjacent the lowermost bores, only transmits water a short distance and from only one pair of waterin bores to the next adjacent pair of water-out bores.

In order to effect cooling of the portion of anode 49 rearwardly of the powder port or passage 64, two additional passages 81 and 82 are drilled at an angle from the cylindrical surface 73 as shown in FIGS. 5b and 6b. Such passages do not extend forwardly as far as the port 64, but instead terminate adjacent thereto. The rear end of one of the passages, number 81, is plugged by a plug 84 (FIG. 6b) which blocks communication between such passage 81 and the annulus 38. Instead, such passage 81 communicates through a radial bore 87 which is drilled through the cylindrical surface 71 and communicates with annulus 39. The other additional passage, number 82, is not plugged but instead communicates with annulus 38.

The forward ends of passages 81 and 82 are caused to communicate with each other through a cross bore 83 which is plugged at one end by a plug 85 (FIG. 6) in order to prevent leakage.

Thus, forwardly-flowing water in annulus 39 passes through radial bore 87 (FIG. 6b), enters passage 81 and passes forwardly, thereafter passes through cross bore 83 to the forward end of passage 82, and thence flows rearwardly through such passage 82 to the annulus 38 for rearward flow through the torch.

Proceeding next to a description of the coolant circuit in the entire torch, and referring particularly to FIGS. 1, 5a and 5b, the water enters through a fitting 89 (FIG. 1) and thus passes upwardly through a copper tube 90 which is soldered to the body of front housing 41 radially-outwardly of the rear end of tube 34. A port 91 through housing 41 conducts the water from tube 90 to an annulus 92 which is defined by front housing 41 around tube 34, such annulus communicating with the previously-described annulus 39 between tubes 33 and 3 1. The water then flows forwardly to the radial bores 75 (FIG. 5b) and 87 (FIG. 6b), thus enters the bores 74 and 81 as described above, and then passes outwardly through the bores 75, 79 (FIG. 6c) and 82 to the annulus 38 which is defined between

concentric tubes

34 and 35.

As shown in FIG. 5a, the rear end of annulus 38 communicates with an annulus 93 defined between front housing 41 and the exterior surface of tube 35. Annulus 93 communicates with an annular groove 94 defined by insulating housing 26 to the rear of the front housing. The annular groove communicates with a substantial number of circumferentially-spaced passages 96 which are formed through insulating housing 26 and extend rearwardly to an annular groove 97 defined by the housing 26 around rear housing 10. Groove 97 communicates with a plurality of radial ports 99 in rear housing 10 and thus with the annulus 14 defined between the inner tubes 12 and 13.

Therefore, water flows through elements 93, 94, 96 and 97 and radially-inwardly through ports 99 to annulus 141, following which the water flows to the left to the forward end of the annulus and thence through a plurality of radial ports 101 (FIG. 5b) to the central passage 102 defined within inner tube 12. The flowing water cools the rear end portion of cathode holder 17 and acts as a heat sink for heat which is transmitted from tungsten slug 22 and element 21 to cathode holder 17. The cathode is thus effectively cooled to increase the life thereof.

From the inner end of the central tube 12, water flows to the right through central passage 102 and thus to the rear end of the central tube 12. It then passes through a communicating passage 103 in rear housing 10 (FIG. 5a) to the fitting 32 and thus to a suitable drain.

The relationship is thus such that only two fittings are required for the water, namely inlet and outlet fittings 39 and 32, yet the water passes to the left, then to the right, then to the left, then to the right for effective cooling of both anode and cathode to maximize the life thereof. The cooling circuits are the same regardless of the lengths of the various concentric tubes.

For high-power operation, for example at 50 kilowatts, the water source shown in FIG. 1 should be a pump which delivers a pressure of about 120-150 psi. The rate of water flow through the torch may be, for example, about 3 gallons per minute.

CURRENT PATHS THROUGH THE TORCH As represented in FIG. 1, the negative terminal of a high-current source of direct power is connected to fitting 32, and the positive terminal of such source is connected to fitting 89. Current therefore flows to the anode through the following path: the positive terminal of the power source, fitting 89, copper tube 90, front housing d1, the various sections of neck 54 of the front housing, the pressure contacts between such neck sections and the exterior surface of the copper outer tube 33 (the pressure having been created by the clamp ring 57), tube 33, the threaded connection 53, and anode 419. Current also flows from the front housing 41 through

tubes

34 and 35 to the anode, but these are less important current paths.

The current path to the cathode from the negative terminal of the current source is through fitting 32, rear housing 111, both of the inner tubes 12 and 13, cathode holder 17, and thence through the threaded shank 19 to the cathode means 20 (formed of the base 21 and the tungsten slug 22).

The current passes between the tip 23 of slug 22 and the wall of arc passage chamber 511 in the form of a high-current arc which heats to a high temperature the gas which is passed through the torch as described be low. The are current may be 1,000 amperes whereas the voltage applied may be 50 volts. Such a high power input, namely 50 kilowatts, is very unusual in such a small-diameter torch, and is made possible by various factors particularly including the means for cooling anode 49.

GAS FLOW AND INJECTOR MEANS Referring particularly to FIGS. 5b and 13, a highly critical element incorporated in the gas flow and injector means is the insulating sleeve or gas injector 1116. Such element 106 not only permits different types of highly-uniform injection of gas (for example, tangential, half-tangential, radial, part radial and part longitudinal, etc.), but also effects electrical insulation as well as serving as a spacing and centering element.

Element 106 has a tubular body the rear end portion of which is counterbored to receive in snug relationship the flange 25 and the previously-described insulating sleeve 16. The part of element 106 which is not counterbored, that is to say the part forwardly of flange 25, receives in snug relationship the main body of cathode holder 17, and also the base 21 of cathode means 211. The insulating sleeve and gas injector 106 extends a substantial distance forwardly of the front edge 1117 of element 21. The forward edge of element 1116 abuts against the rear edge of anode 49 at a region spaced rearwardly from the forward edge of tube 35.

The region of element 106 forwardly of edge W7 cooperates with the rear end portion of the anode 19 in defining an annulus 1113 around the exposed base portion of tungsten slug 22, and into which gas in injected as next described. The forward region of annulus 1113 is between anode wall 52 and the cylindrical surface of the tungsten slug.

As best shown in FIG. 13, a substantial number of longitudinal, circumferentially-spaced shallow grooves 110 are formed in the exterior surface of element 111%, being separated from each other by flutes or ribs 111. Grooves 1111 commence at a region spaced rearwardly from the forward edge of element 1116. Thus, there is formed adjacent such forward edge of element 11% a solid wall 1 12 which substantially blocks flow of gas out the forward ends of grooves 110.

Instead of passing out the forward ends of the grooves, the gas is constrained to flow radially-inwardly through a plurality of circumferentially-spaced passages 113 (FIGS. 5b, 4 and 13), one for each groove 110, and into the described annulus 1113.

As shown in FlG. 1, passages 113 are generally tangential to the annulus. However, as above indicated, for some applications such passages 113 may be radial or may be pointed in any desired direction.

The grooves 113 and the passages 113 cooperate with each other to effect a highly uniform flow of gas into the annulus 108, and in the precise manner desired by the designer. When another type of gas flow is desired, it is merely necessary to substitute a sleeve having different holes. Furthermore, the described construction is particularly susceptible to very smalldiameter torches, it being understood that the outer diameter of the actual sleeve and gas injector element .106 may be only a little over one-half inch. The number of grooves and corresponding injector passages 113 may be much greater (or less) than that shown, for example may be 12 or 16.

The arc gas enters the torch through a fitting 115 (FIG. 1) and thus enters a brass tube 116 for flow to a brass block 117 which is inserted into a recess in the underside of insulating housing 26. Tube 116 is soldered to block 117, and the block is secured to housing 26 by screws, not shown.

The upper end of block 117 fits in a conical portion of the recess in insulating housing 26, FIG. 5a, and has a passage 118 therethrough which communicates with a port 119, the latter leading to an annulus 121 defined by a portion of housing 26 to the rear of tube 35. The annulus 121 communicates with the annulus 36 between tube 35 and the insulating sleeve 16. Thus, gas flows through annulus 36 to the rear end portion of element 106, whereupon such gas enters the rear ends of grooves 110 and then flows forwardly to the injector passages 113 and into annulus 108. The outer surfaces of flutes 111 abut the interior wall of tube 35, thus separating the grooves 111 from each other.

Assuming that the gas injection is tangential as shown, the gas swirls around the tungsten slug 22 in annulus 108, passes forwardly around the tip 23 of the tungsten slug, and passes in swirling manner through the arc passage 50 where such gas is heated to a very high temperature by the electric arc. Spray powder is introduced into the heated gas through port 64 as described above, and is thus deposited on a substrate.

The insulating sleeve and gas injector element 106 is formed of a temperature-resistant material, for example, a suitable ceramic. The preferred material is boron nitride (a ceramic), but another material which may be employed is transite (transite being asbestos bonded in cement).

SEALING MEANS FOR THE WATER AND GAS It is a feature of the present construction that only two O-rings are employed relative to the anode 49, and these are spaced sufficiently far from the arc passage 50, and/or are water cooled, in such manner that very much power may be generated in the arc passage without damaging the O-rings. The first such O-ring (numbered 122, FIG. 5b) is provided radially-inwardly of the forward end of exterior tube 33. The second such ring (numbered 123) is provided radially-inwardly of the forward end of tube 35.

Referring next to FIG. a, O-

rings

124, 125 and 126 are respectively provided around the rear end portions of

tubes

33, 34 and 35. Another O-ring, numbered 127, is provided around the rear portion of the body of front housing 41.

O-

rings

128 and 129 are provided around rear housing on opposite sides of annular groove 97, and an O-ring 131 is provided around a neck portion of the block 117 for the arc gas.

THE HANDLE AND SUPPORT MEANS Although the torch is fully operative as thus far described, it is a feature thereof that external handle and enclosure means may be provided to permit the torch to be hand held in convenient manner.

The illustrated handle comprises corresponding

halves

132 and 133 which meet at a line 134 of abutment as shown in FIG. 2. The

halves

132 and 133 are shaped to enclose the insulating housing 26 and associated parts, and to provide a pistol grip around the tubes and 116.

Halves

132 and 133 are grooved to receive, and lock in place, the powder tube 68. The halves are preferably formed of a phenolic or other suitable plastic.

Handle halves 132 and 133 are readily mounted together by means of three screws 136-138 which extend therethrough. The latter screw, 138, extends through a notch 139 (FIG. 5a) which is provided in the upper edge of insulating housing 26. Thus, screw 138 locks the handle against longitudinal shifting relative to the insulating housing 26.

Instead of being hand-held, the pistol grip portion of elements 132133 may be mounted in a suitable support which is indicated schematically at 141 in FIG. 12. Alternatively, the

elements

132 and 133 may be omitted and the support directly applied to the insulating housing 26.

DESCRIPTION OF ADDITIONAL ANODES It is an important advantage of the anode construction described in detail relative to FIGS. 5b, 6, 6a, 6b and 6c, that the same type of construction and cooling may be employed not only in relation to straight-flow subsonic torches but also for angular flow and/or supersonic torches. Angular flow torches are highly important, for example in the coating of the interiors of small-diameter pipes. Supersonic torches provide vastly superior coating qualities.

Referring first to FIG. 8, a 45 anode is indicated at 49a, as employed in spray-coating the interior of a pipe (shown in phantom). Such anode has an arc passage 50a which, at a distance spaced downstream from the tip 23 of tungsten slug 22, bends at a 45 angle. The downstream end of the angular passage 50a terminates at a face 151, which is perpendicular to the downstream portion of passage 50a. The overall diameter of the front end of the torch is substantially the same as that shown in FIG. 5b.

The powder port 64a extends perpendicular to the downstream portion of passage 50a, and communicates with the block 650 and thus with the powder tube 68a previously described, the latter being held in position by a clip 70.

Except as described, the 45 anode 49a is identical to the one described relative to number 49 in FIG. 5b, etc.

FIG. 9 illustrates a 90 anode 49b. Such anode corresponds to anode 49a except that the arc passage 50b bends at a 90 angle. As is the case relative to 45 anode 49a, the manner of cooling of anode 49b is the same as was described relative to anode 49 of FIG. 5b, etc.

FIG. 10 illustrates a supersonic anode nozzle 490 having a convergent-divergent arc passage 500 into which powder is injected through a passage 640 as described in detail relative to my copending patent application Ser. No. 143,956, for Method and Apparatus for Supersonic Plasma Spray and which was executed on May 13, 1971. The supersonic nozzle 490 may also be made angular, as described in such copending application.

Instead of providing the 45 nozzle or the 90 nozzle as shown in FIGS. 8 and 9, different angles may be provided. Such angles are normally in the range of 45 to 90 USE IN COATING INTERIORS OF PIPES Referring to FIG. 12, a pipe or tube 144, the interior of which is to be spraycoated, is illustrated as mounted in horizontal manner in a feeding and support apparatus M6. Apparatus 146 effects rotation of the pipe 144 about the longitudinal axis thereof and, furthermore effects gradual feeding of the pipe 144 along its axis.

An elongated torch, of one of the angular types described above, is fixedly mounted generally coaxially of the pipe 144 by means of the above-indicated mounting means 141. As stated heretofore, the torch may be any desired length, for example, 10 or feet.

In operation, the torch is started (by high-frequency starting means, or other means) and the apparatus 146 is operated to rotate the pipe 144 about its axis and to feed the pipe at a predetermined speed along its axis. The pipe interior is thus coated as desired. Thereafter, the pipe is removed from the apparatus 146 and reversed, so that the other half of the pipe may be coated. Pipe lengths up to forty feet or more may thus be interiorly spray-coated with corrosion-resistant or wearresistant material] FIG. lll illustrates an embodiment wherein the 90 nozzle 49b described relative to FIG. 9 is provided with an adapter neck 146a which is soldered or otherwise suitably secured to the anode 49b. Neck 146a is interiorly threaded to receive the exteriorly-threaded base M7 of a fitting having another exteriorly-threaded portion 148 to which the end of a support pipe 149 is threaded. In the described manner, the support pipe M19 is extended into the end of the pipe remote from the handle portion of the torch, thus affording an additional degree of support when the torch is employed to coat the interior of a pipe 144. The water-cooling means for anode 49b is not shown in FIG. 11 but is nevertheless present (as shown in FIG. 9).

Although the anode 49b shown in FIG. 11 is of the 90 type, it may also be of the 45 type or it may have another angle.

The words temperature-resistant insulating sleeve" refer to a sleeve which is resistant to very high temperatures.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

I claim:

ll. An elongated electrical plasma-jet torch adapted to be manufactured in various desired lengths, which comprises:

an insulating housing,

a metallic front housing mounted in the forward portion of said insulating housing,

first and second concentric tubes removably and sealingly inserted into said front housing,

said tubes having diameters sufficiently different from each other to form a first annulus therebetween,

LII

at least one of said first and second tubes being an electrical conductor, and being electrically con nected to said front housing,

a third tube mounted concentrically within said first and second tubes,

said third tube having a diameter sufficiently small that a second annulus is defined outwardly adjacent said third tube,

said third tube being inserted rearwardly through said front housing into said insulating housing and being sealingly associated with said insulating housing,

an anode nozzle removably and sealingly mounted at the forward ends of said first and second tubes, said anode nozzle having coolant flow means therein, an inlet portion of said coolant flow means communicating with one of said first and second annuli, an outlet portion of said coolant flow means communicating with the other of said first and second annuli, said anode nozzle being electrically connected to at least said electrically conductive one of said first and second tubes, an elongated cathode assembly removably inserted forwardly through said insulating housing, through said front housing, and through said third tube, the forward portion of said cathode assembly being a cathode which is mounted in said anode nozzle, said cathode assembly having an outer diameter sufficiently small that a gas-flow path is formed therearound and within said third tube, means to effect flow of coolant in series through said first and second annuli and through said coolant flow means in said anode nozzle,

means to connect a source of power to said front housing and to the rear end of said cathode assembly, and

means to pass arc gas into said gasflow path around said cathode assembly and thus to said nozzle,

said means to pass arc gas into said gas-flow path including gas flow means defined by said insulat ing housing and communicating with the interior of said third tube.

2. An elongated electrical plasmajet torch adapted to be manufactured in various desired lengths, which comprises:

an insulating housing,

at least one of said first and second tubes being an electrical conductor, and being electrically connected to said front housing,

a third tube mounted concentrically within said first and second tubes,

an anode nozzle removably and sealingly mounted at the forward ends of said first and second tubes,

said anode nozzle having coolant flow means therein, an inlet portion of said coolant flow means communicating with one of said first and second annuli, an outlet portion of said coolant flow means communicating with the other of said first and second annuli, said anode nozzle being electrically connected to at least said electrically conductive one of said first and second tubes, an elongated cathode assembly removably inserted forwardly through said insulating housing, through said front housing, and through said third tube, the forward portion of said cathode assembly being a cathode which is mounted in said anode nozzle,

said cathode assembly having an outer diameter sufficiently small that a gas-flow path is formed therearound and within said third tube,

said cathode assembly including fourth and fifth concentric tubes which are concentric with said first, second and third tubes,

said fourth and fifth tubes being connected to an electrically and thermally conductive holder for said cathode,

at least one of said fourth and fifth tubes being an electrical conductor,

said fourth and fifth tubes having diameters sufficiently different from each other that a third annulus is defined therebetween,

means provided at the forward ends of said fourth and fifth tubes to effect communication between said third annulus and the central passage through the innermost one of said fourth and fifth tubes,

a metallic rear housing mounted in the rear portion of said insulating housing and connected to said fourth and fifth tubes,

means to effect flow of coolant in series through said first and second annuli and through said coolant flow means in said anode nozzle,

means to pass coolant in series through said third annulus and through said central passage,

means to connect a source of power to said front housing and to said rear housing, and

means to pass arc gas into said gas-flow path around said cathode assembly and thus to said nozzle.

3. The invention as claimed in claim 2, in which said means to pass coolant through said third annulus and through said central passage includes a series connection with said means to effect series flow of coolant through said first and second annuli, said series connection comprising:

an annular groove defined by said insulating housing around the rear end of said third tube and communicating with said second annulus,

passage means formed in said insulating housing and extending therethrough from said annular groove to an annular groove around said rear housing, and

port means in said rear housing and extending from said last-mentioned annular groove to said third annulus between said fourth and fifth tubes.

4. An electrical plasma-jet torch the forward portion of which may have a very small diameter in comparison to the electrical power supplied to the torch, said torch comprising:

an anode nozzle,

said anode nozzle comprising a thick-walled tube formed of highly conductive metal, the thick wall of said tube having a substantial number of circumferentially spaced longitudi- 5 na] bores extending therethrough,

means to connect to each other the forward portions of one group of said bores and the forward portions of another group of said bores, whereby said one group may conduct water in one direction and said other group may conduct water in the opposite direction and in series with said one group,

first, second and third concentric tubes extending longitudinally of said anode nozzle and having sufficiently different diameters that a first annulus is defined between the outer two of said three tubes and a second annulus is defined between the inner two of said three tubes,

at least one of said three concentric tubes being an electrical conductor,

said third tube being the innermost one of said three tubes,

means to connect said first annulus to the rear portions of said one group of bores,

means to connect said second annulus to the rear portions of said other group of bores,

an elongated and electrically conductive cathode as sembly mounted longitudinally within said third tube,

said cathode assembly including an elongated cathode at least the forward part of which is disposed coaxially within said anode nozzle,

said cathode assembly having an outer diameter sufficiently small that gas may be passed forwardly therearound and within said third tube,

a temperature-resistant insulating sleeve mounted closely around at least the forward part of said cathode assembly and within said third tube,

the outer diameter of at least parts of said sleeve being sufficiently small that gas flowing for wardly within said third tube will pass between the inner wall of said third tube and the exterior surface of said parts of said sleeve,

passage means extending inwardly through said sleeve at said small-diameter parts thereof, and conducting gas to the interior of said anode nozzle adjacent said cathode and rearwardly of the forward portion of said cathode,

means to pass current through the conductive one of said three tubes to said anode nozzle, and to pass current through said cathode assembly to said cathode,

means to pass water into the rear portion of one of said first and second annuli and to draw water out of the rear portion of the other of said first and second annuli, and

means to pass gas forwardly through said third tube,

around at least said parts of said sleeve, and through said passage means to the interior of said anode nozzle.

5. The invention as claimed in claim 4, in which a powder port is provided in said anode nozzle at a portion thereof which is not penetrated by said bores, and in which a powder tube is connected at the forward end thereof to said powder port, said powder tube extend ing longitudinally and exteriorly of the outermost one of said three concentric tubes.

6. The invention as claimed in claim 4, in which the diameter of the central passage through said anode nozzle tube is in excess of one-third the outer diameter of said anode nozzle tube.

7. The invention as claimed in claim 4, in which said insulating sleeve has a substantial number of circumferentially spaced longitudinal flutes formed exteriorly thereon, the grooves between said flutes being outwardly adjacent said small-diameter parts of said sleeve, said flutes engaging the interior surface of said third tube, whereby gas flowing forwardly through said third tube and around said cathode assembly is constrained to enter said grooves and pass there-through to said passage means and then to the interior of said anode nozzle.

8. The invention as claimed in claim 7, in which said insulating sleeve is formed of a material selected from a group consisting of boron nitride and transite.

9. The invention as claimed in claim 4, in which an additional insulating sleeve is provided around the rear portion of said cathode assembly and extends forwardly to said temperature-resistant insulating sleeve.

10. The invention as claimed in claim 4, in which a generally tubular electrically conductive front housing is mounted coaxially around the rear ends of the outer two of said first, second and third concentric tubes, in which the outermost one of said three tubes is electrically conductive, in which said means to pass current includes a low-resistance connection between said front housing and said outermost tube, in which said front housing is shaped to define an annulus around the rear end of the intermediate one of said three tubes, said rear end of said intermediate tube protruding rearwardly from the rear end of said outermost tube, in which said annulus forms part of said means to pass water, in which an insulating housing is mounted around said front housing and around the rear end of said third tube, said rear end of said third tube protruding rearwardly from said intermediate one of said three tubes, and in which said insulating housing defines an annulus around the rear end of said cathode assembly, said lastmentioned annulus forming part of said means to pass gas.

11. The invention as claimed in claim 10, in which O-rings are provided to removably and sealingly associate said outermost tube and said intermediate tube with said front housing, and to removably and sealingly associate said third tube with said insulating housing, in which said cathode assembly extends rearwardly through said front housing and said insulating housing to a rear housing, in which said cathode assembly has water passages therethrough, and in which means are provided in said insulating housing and in said rear housing to conduct water to said water passages from the rear end of the annulus defined between said third tube and said intermediate tube.

12. The invention as claimed in claim 11, in which said cathode assembly comprises fourth and fifth concentric tubes at least one of which is electrically conductive, said tubes defining an annulus therebetween and which forms one of said water passages in said cathode assembly, the other water passage in said cathode assembly being through the innermost one of said fourth and fifth tubes, in which means are provided to effect communication between the forward ends of said water passages in said cathode assembly, in which the rear ends of said fourth and fifth tubes are mounted sealingly in said rear housing, and in which said rear housing is an electrical conductor and forms part of the means to pass current.

13. The invention as claimed in claim 4, in which protuberances are provided exteriorly at spaced points on said third tube and on said intermediate one of said three tubes, said protuberances being dimensioned to maintain said three tubes in concentric relationship.

14. An anode nozzle for an electrical plasma-jet torch, which comprises:

a thick-walled tube of highly conductive metal,

the central passage in said tube being an arc passage or chamber of the anode nozzle,

said tube having a substantial number of bores formed longitudinally therethrough in circumferentially spaced relationship around said central passage,

the outermost part of said thick-walled tube being adapted to be inserted coaxially into the end of a first elongated tube and in sealed relationship to such end,

a portion of the rear end of said thick-walled tube having a reduced diameter and being adapted to be partially inserted coaxially into the end of a second elongated tube having a diameter smaller than that of said first elongated tube, whereby a first generally cylindrical portion of said thick-walled tube is adapted to be exposed to an annulus defined between said first and second elongated tubes,

a second portion of the rear end of said thickwalled tube having a further reduced diameter and being adapted to be partially inserted coaxially into the end of a third elongated tube having a diameter smaller than that of said second elongated tube, whereby a second generally cylindrical portion of said thick-walled tube is adapted to be exposed J to an annulus defined between said second and third elongated tubes,

said second generally cylindrical portion being offset from said first generally cylindrical portion in a direction longitudinally of said thickwalled tube,

means to connect the forward end portions of one group of said bores to the forward end portions of another group of said bores,

first connector means adapted to connect the rear end portions of said one group to a coolant-inlet means,

said first connector means comprising bores to extend said one group of said bores to said first generally cylindrical portion for communication with said annulus defined between said first and second elongated tubes, and

second connector means adapted to connect the rear end portions of said other group to a coo- [ant-outlet means,

. said second connector means comprising bores to extend said other group of said bores to said second generally cylindrical portion for communication with said annulus defined between said second and third elongated tubes.

15. An anode nozzle for an electrical plasma-jet torch, which comprises: i

a thick-walled tube of highly conductive metal,

said tube having a port extended through one side portion thereof for injection of powder into said central passage,

said one group of bores and said other group of bores not extending through said side portion of said thickwalled tube in which said injector port is located,

first connector means adapted to connect the rear end portions of said one group to a coolant-inlet means, second connector means adapted to connect the rear end portions of said other group to a coolant-outlet means,

two additional bores formed longitudinally through said thick-walled tube on the same side thereof as that on which said injection port is located,

said two additional bores being disposed rearwardly of said injection port,

the forward ends of said two additional bores being connected to each other,

means for connecting the rear end of one of said two additional bores to said coolant-inlet means, and means provided for connecting the rear end of the other of said two additional bores to said coolantoutlet means.

16. The invention as claimed in claim 15, in which said central passage bends at an angle from the axis of the rear portion of said thick-walled tube, in which said injection port communicates with the downstream portion of said central passage on the opposite side of the bend from the upstream end of said central passage, and in which said downstream of said central passage is on the same side portion of said thick-walled tube as is said injection port, whereby said two additional bores permit water cooling of said side of said thick-walled tube despite the bend in said central passage and despite the presence of said injection port.

17. The invention as claimed in claim 16, in which the angle of said bend is in the range of about 45 to about 90.

18. An electrical plasma-jet torch, which comprises:

wall means to define an elongated cylindrical passage,

an elongated anode nozzle having a central arc passage therethrough, the rear end of said arc passage being adjacent and communicating coaxially with the forward end portion of said cylindrical passage, an elongated cathode slug having an outer diameter substantially smaller than the diameter of at least the rear portion of said are passage, the forward portion of said cathode slug being positioned coaxially within the rear portion of said are passage and spaced radially inwardly from the wall of said are passage, whereby an annulus is defined around said cathode slug and within said arc passage, an electrically conductive cylindrical cathode base mounted longitudinally of and within said cylindrical passage, said cathode base having an outer diameter substantially smaller than the diameter of said cylindrical passage, said cathode base being connected coaxially to the rear end of said cathode slug to support the same and conduct current thereto, an elongated temperature-resistant ceramic sleeve mounted coaxially around said cathode base, the forward end of said sleeve extending forwardly past the forward end of said cathode base and defining a second annulus around said cathode slug, said second annulus communicating coaxially with said first-mentioned annulus, means to pass gas from the rear portion of said cylindrical passage around the exterior of said sleeve to the forward end portion of said sleeve, said means to pass said gas comprising a substantial number of circumferentially spaced longitudinal grooves formed in the exterior of said sleeve, said grooves being separated from each other by flutes which extend radially outwardly to said wall means, passage means formed through the forward end portion of said sleeve and communicating with said second annulus to inject said gas therein, said passage means comprising a bore formed through said sleeve at the forward end portion of each of said grooves, the inner end of each of said bores terminating at said second annulus, and means to pass electricity to said anode nozzle and to said cathode base whereby to generate an arc in said arc passage forwardly of said cathode slug to thus heat said gas prior to discharge thereof from said arc passage.

22 g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pat 3.740. 522 Dated June 19, 1973 lnv n fl Erich Muehlberger It is certified that error appears in the above-identified patent and that said Letters Patent are hereby .corrected as shown below:

Column 19, line 40, after "downstream", insert -portion-.

Column 19, line 41, cancel portion".

Signed and sealed tnis 18th day of Decemoer 1973.

(SEAL) Attest:

EDWARD NI. FLETCHER, RENE D. TEUTTT TEXER Attesting; Officer Acting Commissioner of Patents

Claims

1. An elongated electrical plasma-jet torch adapted to be manufactured in various desired lengths, which comprises: an insulating housing, a metallic front housing mounted in the forward portion of said insulating housing, first and second concentric tubes removably and sealingly inserted into said front housing, said tubes having diameters sufficiently different from each other to form a first annulus therebetween, at least one of said first and second tubes being an electrical conductor, and being electrically connected to said front housing, a third tube mounted concentrically within said first and second tubes, said third tube having a diameter sufficiently small that a second annulus is defined outwardly adjacent said third tube, said third tube being inserted rearwardly through said front housing into said insulating housing and being sealingly associated with said insulating housing, an anode nozzle removably and sealingly mounted at the forward ends of said first and second tubes, said anode nozzle having coolant flow means therein, an inlet portion of said coolant flow means communicating with one of said first and second annuli, an outlet portion of said coolant flow means communicating with the other of said first and second annuli, said anode nozzle being electrically connected to at least said electrically conductive one of said first and second tubes, an elongated cathode assembly removably inserted forwardly through said insulating housing, through said front housing, and through said third tube, the forward portion of said cathode assembly being a cathode which is mounted in said anode nozzle, said cathode assembly having an outer diameter sufficiently small that a gas-flow path is formed therearound and within said third tube, means to effect flow of coolant in series through said first and second annuli and through said coolant flow means in said anode nozzle, means to connect a source of power to said front housing and to the rear end of said cathode assembly, and means to pass arc gas into said gas-flow path around said cathode assembly and thus to said nozzle, said means to pass arc gas into said gas-flow path including gas flow means defined by said insulating housing and communicating with the interior of said third tube.

2. An elongated electrical plasma-jet torch adapted to be manufactured in various desired lengths, which comprises: an insulating housing, a metallic front housing mounted in the forward portion of said insulating housing, first and second concentric tubes removably and sealingly inserted into said front housing, said tubes having diameters sufficiently different from each other to form a first annulus therebetween, at least one of said first and second tubes being an electrical conductor, and being electrically connected to said front housing, a third tube mounted concentrically within said first and second tubes, said third tube having a diameter sufficiently small that a second annulus is defined outwardly adjacent said third tube, an anode nozzle removably and sealingly mounted at the forward ends of said first and second tubes, said anode nozzle having coolant flow means therein, an inlet portion of said coolant flow means communicating with one of said first and second annuli, an outlet portion of said coolant flow means communicating with the other of said first and second annuli, said anode nozzle being electrically connected to at least said electrically conductive one of said first and second tubes, an elongated cathode assembly removably inserted forwardly through said insulating housing, through said front housing, and through said third tube, the forward portion of said cathode assembly being a cathode which is mounted in said anode nozzle, said cathode assembly having an outer diameter sufficiently small that a gas-flow path is formed therearound and within said third tube, said cathode assembly including fourth and fifth concentric tubes which are concentric with said first, second and third tubes, said fourth and fifth tubes being connected to an electrically and thermally conductive holder for said cathode, at least one of said fourth and fifth tubes being an electrical conductor, said fourth and fifth tubes having diameters sufficiently different from each other that a third annulus is defined therebetween, means provided at the forward ends of said fourth and fifth tubes to effect communication between said third annulus and the central passage through the innermost one of said fourth and fifth tubes, a metallic rear housing mounted in the rear portion of said insulating housing and connected to said fourth and fifth tubes, means to effect flow of coolant in series through said first and second annuli and through said coolant flow means in said anode nozzle, means to pass coolant in series through said third annulus and through said central passage, means to connect a source of power to said front housing and to said rear housing, and means to pass arc gas into said gas-flow path around said cathode assembly and thus to said nozzle.

3. The invention as claimed in claim 2, in which said means to pass coolant through said third annulus and through said central passage includes a series connection with said means to effect series flow of coolant through said first and second annuli, said series connection comprising: an annular groove defined by said insulating housing around the rear end of said third tube and communicating with said second annulus, passage means formed in said insulating housing and extending therethrough from said annular groove to an annular groove around said rear housing, and port means in said rear housing and extending from said last-mentioned annular groove to said third annulus between said fourth and fifth tubes.

4. An electrical plasma-jet torch the forward portion of which may have a very small diameter in comparison to the electrical power supplied to the torch, said torch comprising: an anode nozzle, said anode nozzle comprising a thick-walled tube formed of highly conductive metal, the thick wall of said tube having a substantial number of circumferentially spaced longitudinal bores extending therethrough, means to connect to each other the forward portions of one group of said bores and the forward portions of another group of said bores, whereby said one group may conduct water in one direction and said other group may conduct water in the opposite direction and in series with sAid one group, first, second and third concentric tubes extending longitudinally of said anode nozzle and having sufficiently different diameters that a first annulus is defined between the outer two of said three tubes and a second annulus is defined between the inner two of said three tubes, at least one of said three concentric tubes being an electrical conductor, said third tube being the innermost one of said three tubes, means to connect said first annulus to the rear portions of said one group of bores, means to connect said second annulus to the rear portions of said other group of bores, an elongated and electrically conductive cathode assembly mounted longitudinally within said third tube, said cathode assembly including an elongated cathode at least the forward part of which is disposed coaxially within said anode nozzle, said cathode assembly having an outer diameter sufficiently small that gas may be passed forwardly therearound and within said third tube, a temperature-resistant insulating sleeve mounted closely around at least the forward part of said cathode assembly and within said third tube, the outer diameter of at least parts of said sleeve being sufficiently small that gas flowing forwardly within said third tube will pass between the inner wall of said third tube and the exterior surface of said parts of said sleeve, passage means extending inwardly through said sleeve at said small-diameter parts thereof, and conducting gas to the interior of said anode nozzle adjacent said cathode and rearwardly of the forward portion of said cathode, means to pass current through the conductive one of said three tubes to said anode nozzle, and to pass current through said cathode assembly to said cathode, means to pass water into the rear portion of one of said first and second annuli and to draw water out of the rear portion of the other of said first and second annuli, and means to pass gas forwardly through said third tube, around at least said parts of said sleeve, and through said passage means to the interior of said anode nozzle.

5. The invention as claimed in claim 4, in which a powder port is provided in said anode nozzle at a portion thereof which is not penetrated by said bores, and in which a powder tube is connected at the forward end thereof to said powder port, said powder tube extending longitudinally and exteriorly of the outermost one of said three concentric tubes.

10. The invention as claimed in claim 4, in which a generally tubular electrically conductive front housing is mounted coaxially around the rear ends of the outer two of said first, second and third concentric tubes, in which the outermost one of said three tubes is electrically conductive, in which said means to pass current includes a low-resistance connection between said front housing and said outermoSt tube, in which said front housing is shaped to define an annulus around the rear end of the intermediate one of said three tubes, said rear end of said intermediate tube protruding rearwardly from the rear end of said outermost tube, in which said annulus forms part of said means to pass water, in which an insulating housing is mounted around said front housing and around the rear end of said third tube, said rear end of said third tube protruding rearwardly from said intermediate one of said three tubes, and in which said insulating housing defines an annulus around the rear end of said cathode assembly, said last-mentioned annulus forming part of said means to pass gas.

14. An anode nozzle for an electrical plasma-jet torch, which comprises: a thick-walled tube of highly conductive metal, the central passage in said tube being an arc passage or chamber of the anode nozzle, said tube having a substantial number of bores formed longitudinally therethrough in circumferentially spaced relationship around said central passage, the outermost part of said thick-walled tube being adapted to be inserted coaxially into the end of a first elongated tube and in sealed relationship to such end, a portion of the rear end of said thick-walled tube having a reduced diameter and being adapted to be partially inserted coaxially into the end of a second elongated tube having a diameter smaller than that of said first elongated tube, whereby a first generally cylindrical portion of said thick-walled tube is adapted to be exposed to an annulus defined between said first and second elongated tubes, a second portion of the rear end of said thick-walled tube having a further reduced diameter and being adapted to be partially inserted coaxially into the end of a third elongated tube having a diameter smaller than that of said second elongated tube, whereby a second generally cylindrical portion of said thick-walled tube is adapted to be exposed to an annulus defined between said second and third elongated tubes, said second generally cylindrical portion being offset from said first generally cylindrical portion in a direction longitudinally of said thick-walled tube, means to connect the forward end portions of one group of said bores to the forward end portions of another group of said bores, first connector means adapted to connect the rear end portions of said one group to a coolant-inlet means, said first connector means comprising bores to extend said one group of said bores to said first generally cylindrical portion for communication with said annulus defined between said first and second elongated tubes, and second connector means adapted to connect the rear end portions of said other group to a coolant-outlet means, said second connector means comprising bores to extend said other group of said bores to said second generally cylindrical portion for communication with said annulus defined between said second and third elongated tubes.

15. An anode nozzle for an electrical plasma-jet torch, which comprises: a thick-walled tube of highly conductive metal, the central passage in said tube being an arc passage or chamber of the anode nozzle, said tube having a substantial number of bores formed longitudinally therethrough in circumferentially spaced relationship around said central passage, said tube having a port extended through one side portion thereof for injection of powder into said central passage, means to connect the forward end portions of one group of said bores to the forward end portions of another group of said bores, said one group of bores and said other group of bores not extending through said side portion of said thickwalled tube in which said injector port is located, first connector means adapted to connect the rear end portions of said one group to a coolant-inlet means, second connector means adapted to connect the rear end portions of said other group to a coolant-outlet means, two additional bores formed longitudinally through said thick-walled tube on the same side thereof as that on which said injection port is located, said two additional bores being disposed rearwardly of said injection port, the forward ends of said two additional bores being connected to each other, means for connecting the rear end of one of said two additional bores to said coolant-inlet means, and means provided for connecting the rear end of the other of said two additional bores to said coolant-outlet means.

17. The invention as claimed in claim 16, in which the angle of said bend is in the range of about 45* to about 90* .

18. An electrical plasma-jet torch, which comprises: wall means to define an elongated cylindrical passage, an elongated anode nozzle having a central arc passage therethrough, the rear end of said arc passage being adjacent and communicating coaxially with the forward end portion of said cylindrical passage, an elongated cathode slug having an outer diameter substantially smaller than the diameter of at least the rear portion of said arc passage, the forward portion of said cathode slug being positioned coaxially within the rear portion of said arc passage and spaced radially inwardly from the wall of said arc passage, whereby an annulus is defined around said cathode slug and within said arc passage, an electrically conductive cylindrical cathode base mounted longitudinally of and within said cylindrical passage, said cathode base having an outer diameter substantially smaller than the diameter of said cylindrical passage, said cathode base being connected coaXially to the rear end of said cathode slug to support the same and conduct current thereto, an elongated temperature-resistant ceramic sleeve mounted coaxially around said cathode base, the forward end of said sleeve extending forwardly past the forward end of said cathode base and defining a second annulus around said cathode slug, said second annulus communicating coaxially with said first-mentioned annulus, means to pass gas from the rear portion of said cylindrical passage around the exterior of said sleeve to the forward end portion of said sleeve, said means to pass said gas comprising a substantial number of circumferentially spaced longitudinal grooves formed in the exterior of said sleeve, said grooves being separated from each other by flutes which extend radially outwardly to said wall means, passage means formed through the forward end portion of said sleeve and communicating with said second annulus to inject said gas therein, said passage means comprising a bore formed through said sleeve at the forward end portion of each of said grooves, the inner end of each of said bores terminating at said second annulus, and means to pass electricity to said anode nozzle and to said cathode base whereby to generate an arc in said arc passage forwardly of said cathode slug to thus heat said gas prior to discharge thereof from said arc passage.