05/133126

06/19/1973

04/12/1971

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Geotel, Inc. (Amityville, Long Island, NY)

219/121.470

219/121.520, 219/121.490, 219/75

B05B7/22; B05B13/06; H05H1/32; H05H1/34; H05H1/28; B05B7/16; H05H1/26; B23K9/00

219/76,121P,74,75 313/231

Truhe V, J.

Peterson, Gale R.

I claim

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

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

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:

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:

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.

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 last-mentioned 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:

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

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:

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 1950's. 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 high-speed 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 torch 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; 3,313,908; 3,390,292.

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 temperature-resisting 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. Such cathode 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 4--4 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. 5b;

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. 6c 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 90° 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, 0.812 inch. This does not include the powder-feed 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 10 (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 coaxially 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 above-described 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 housing.

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, arc 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. Referring to FIGS. 5a-5b, 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 arc 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 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.

Except for the described arc 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 radially-inwardly 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 arc 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 U.S. 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. 5b, 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 outwardly-spaced 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 50 (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. 6c) 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 75 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 cross-sectional 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 water-in 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 34. The water then flows forwardly to the radial bores 78 (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 14, 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 89 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 41, 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 49. 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 10, 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 50 in the form of a high-current arc which heats to a high temperature the gas which is passed through the torch as described below. The arc 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 106. 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 20. The insulating sleeve and gas injector 106 extends a substantial distance forwardly of the front edge 107 of element 21. The forward edge of element 106 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 107 cooperates with the rear end portion of the anode 49 in defining an annulus 108 around the exposed base portion of tungsten slug 22, and into which gas in injected as next described. The forward region of annulus 108 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 106, being separated from each other by flutes or ribs 111. Grooves 110 commence at a region spaced rearwardly from the forward edge of element 106. Thus, there is formed adjacent such forward edge of element 106 a solid wall 112 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 108.

As shown in FIG. 4, 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 110 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 small-diameter 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 O-ring (numbered 123) is provided radially-inwardly of the forward end of tube 35.

Referring next to FIG. 5a, 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 10 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 90 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 132-133 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 65a 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 49c having a convergent-divergent arc passage 50c into which powder is injected through a passage 64c 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 49c 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 spray-coated, is illustrated as mounted in horizontal manner in a feeding and support apparatus 146. 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 20 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 wear-resistant material.

FIG. 11 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 147 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 149 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.