US2714563A - Method and apparatus utilizing detonation waves for spraying and other purposes - Google Patents

Description

Aug. 2, 1955 PQORMAN ETAL 2,714,563

METHOD AND APPARATUS UTILIZING DETONATION WAVES FOR SPRAYING AND OTHER PURPOSES Filed March 7, 1952 2 Sheets-Sheet l I 17 s xjg; COIL 7 i Q; ACETYLENE' 2 ACETYLENE 28 INVENTORS RICHARD M. POORMAN YG HERBERT B.SARGENT OX EN g HEADLEE LAMPREY A'TToRNEY g- .g. i

Aug. 2, 1955 R. M. POORMAN ET AL 2,714,563

METHOD AND APPARATUS UTILIZING DETONATION WAVES FOR SPRAYING AND OTHER PURPOSES Filed March 7, 1952 2 Sheets-Sheet 2 Ed 33 WW 03 4.

32 I I SPARK COIL 2 ACETYILENE+ POWDER A A A Tl W6 (Tungsten Carbide alloy) (Steel base) INVENTORS J 5 RICHARD M. POORMAN y- HERBERT B. SARGENT r I HEADLEE LAMPREY h AT ORNEY METHOD AND APPARATUS UTILIZING DETONA- TION WAVES FOR SPRAYING AND OTHER PURPGSES Richard M. Poorman, Speedway, and Herbert B. Sargent, Indianapolis, Ind, and Headlee Lamprey, Lakewood, Ghio, assignors to Union Carbide and Carbon Corporation, a corporation of New York Application March 7, 1952, Serial No. 275,332

27 Ciaims. (Cl. 117105) This invention relates to new methods of using detonations and to novel apparatus for making, controlling, and using detonations.

By the term detonation is meant a very rapid combustion in which the flame front moves at velocities higher than the velocity of sound in the unburned gases, and therefore characterized as supersonic velocities. (Typical calculated velocities of sound at normal pressure are 1085 feet per second at 18 C. in a 50% oxygen-50% acetylene mixture, 1384 in the same mixture at 200 C., and 1122 at 18 C. in a 9.5% acetylene-90.5% air mixture; in air at 18 C. the sonic velocity is calculated as 1122 feet per second.) The rate of flame propagation is far greater in a detonation than in an explosion, which is a combustion in which the velocity of flame propagation does not exceed the velocity of sound in the unburned gases. According to Wilhelm Josts Explosion and Combustion Processes in Gases. McGraw-Hill Book Co., Inc., New York (1946), pages 160 to 210 of which are devoted to detonations, the velocity of the flame front in detonations thus far investigated is from 1 to 4 kilometers per second (about 3,280 to 13,120 feet per second), as compared to, for instance, 50 feet per second for a typical explosion.

The flame of a detention moves into the unburned gas with a velocity which is supersonic instead of subsonic, and it is initiated by and remains associated with a shock front. Once established in a long tube, the detonation wave travels at a constant velocity (Lewis and Von Elbe, Combustion, Flames and Explosions, Academic Press Inc., 1951).

Detonations in gases have not been considered commercially useful. Where they have occurred they have been objectionable. An object of this invention is to utilize the phenomenon of a detonation in helpful and valuable ways. For example, the invention uses detonations to impart a high velocity and a high temperature to particles, and to project the speeding particles against a surface for coating, cleaning, breaking, or boring, and for other purposes.

In accordance with the invention, a single fluid fuel charge or a rapid succession of fluid fuel charges of proper composition to be detonated are fed to a gun where they are ignited to establish a single detonation or a series of detonations following one another at short time intervals. Into this gun, in one aspect of the invention, particles such as powder are introduced in such manner that they are accelerated by the detonation and its associated phenomena and projected from the open end of the gun onto a surface.

The invention will be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a view, partly diagrammatic, of one form of detonation gun embodying the invention;

Fig. 2 is a view of a modification of the gun shown in Fig. 1;

Fig. 3 is a view, also partly diagrammatic, of a further modification of the gun shown in Fig. 1;

Eatented Aug. 2, 1955 Fig. 4 is a side elevational view, also partly diagrammatic, of still another modification of a detonation gun; and

Fig. 5 is a photomicrograph, at 300 diameters magnification, showing a layer of tungsten carbide-cobalt alloy deposited on a steel workpiece by the method of the invention.

According to the embodiment shown in Fig. 1, a combustible gas, such as acetylene, is supplied through a pipe 10, and an oxidizing gas, such as air, is supplied through a pipe 11, to a mixing chamber 12 where they form a detonating gaseous charge mixture which moves through a short connecting pipe 13 into an ignition chamber 14 provided with a spark plug 15. Sparking of the spark plug 15 ignites the charge, leading to the formation of a detonation wave which travels through a barrel 16 of the gun and out its open end. The firing of the spark plug 15 is accomplished by a spark coil 17, battery 13, and cam operated switch 19. The frequency of firing is regulated by a variablespeed motor 20 which drives the cam of the switch 19.

Powder is introduced into and carried by the oxidizing gas fed through the pipe 11, or it may be carried by the combustible gas. The powder particles are heated and accelerated by the detonation waves and propelled from the open end of the gun barrel 16 at high velocities.

in the modification shown in Fig. 2, powder is fed into the air inlet pipe 1., from a container 21 at a rate controlled by a valve 22. A pressure equalizing line 23 leads from the upstream side of the powder introduction point 24 to the headspace of the powder container 21. To promote thorough mixing of the combustible gas and the oxidant the former is introduced into the mixing chamber 12 from two opposite sides through pipes 10 and 10a. Detonation conditions are improved by providing a small ignition chamber 140: of initially less diameter than that of the barrel 16, which diameter gradually increases towards the barrel.

We have found that under some operating conditions, for instance when using oxygen and acetylene, it is desirable to have a positive closure between the ignition chamber and the gas supply. Also, under some circumstances, for instance when using very fine powder or low melting powders, it is advantageous to introduce the powder downstream of the ignition chamber so that the power will not deposit in the chamber. These features are indicated in Fig. 3 which shows poppet valves 25 operated in conventional fashion by a motor 26 and cam 27 to obtain the desired frequency of opening and closing of the valves. A powder introduction pipe 28 is shown between the ignition chamber 14 and the open end of the gun barrel 16. Coatings have also been made when the powder was introduced between the open end of the barrel and the workpiece.

The detonation gun shown in Fig. 4 is similar to that of Fig. 3 except that an inert gas such as nitrogen is introduced into the gun from a conduit 29 through a poppet valve 31, to purge the mixing chamber and thereby protect the valves. Valve 31 is operated by a second cam 32 on cam shaft 33 which is so constructed and arranged relatively to cam 27 and so correlated with a spark timing cam 34 that the following timed sequence of operations occurs:

1. Cam 27 opens poppet valves 35 and 37 simultaneously to admit combustible gas and oxidant (with or without powder) to the gun.

2. Cam 27 then permits poppet valves 35 and 37 to close.

3. Immediately after valves 35 and 37 close, cam 32 opens poppet valve 31 and admits inert nitrogen gas to the gun. Nitrogen gas flows across valves 35 and 37 to dilute any leaks from such valves which might cause flashback upon detonation of the mixture.

4. Immediately after nitrogen valve 31 opens, and while it remains open, cam 34 fires the gun.

5. After detonation occurs nitrogen from open valve 31 flows through the gun to drive out the hot combustion products, and forms a protective wall between them and the next combustible mixture charge.

' 6. Cam 32 then permits nitrogen valve 31 to close and the cycle is ready to repeat with the reopening of valves 35 and 37 to form the next combustible mixture.

There is wide latitude of choice in the dimensions of the gun barrel 16, provided that the length is at least several times the diameter of the bore. If the barrel is too short, the gas mixture will not detonate. At oneinch inner diameter We have successfully used lengths from fifteen to one hundred and twenty inches. Somewhat shorter barrels are much less efiicient although usable with some gas mixtures. Our best results with one-inch inner diameter barrels have been achieved with barrel lengths from three to six feet. Using /2 inch inner diameter pipe we have found a length of eight inches to be usable with some gas mixtures but three feet to be more generally suitable.

Simple air cooling is ordinarily adequate for the gun barrel. If in a particular use of the gun, for instance for nearly continuous use with oxygen-acetylene mixtures it is found that the barrel gets too hot, it may be water cooled. Poorly cooled corners and edges within the ignition and mixing chambers should of course be avoided to prevent the development of hot spots which could cause too early ignition.

The forms of apparatus shown in Figs. 1 and 2 operate without valves in the gas lines. In these forms the oxidizing and fuel gases should be supplied at about the same pressure to reduce the danger of backfire. A conventional backfire arrester may be inserted in the fuel supply line for greater safety.

The detonation Wave may be generated in a wide variety of fluids and fluid mixtures. Liquid fuels such as gasoline may be vaporized and used. Solid fuels such as coal powder may be suspended as dusts in a gas to make a fluid mixture. Suitable gaseous fuels include acetylene, hydrogen, propane, butane, pentane, and

ethylene which form detonatable mixtures with an Detonation Wave Mixture fg Approx. Velocity, ft. per sec.

Hydrogen-air 29 6, 360 Acetylene-air 9 7, 200 Propane-oxygen 29 8. 540 Hydrogen-oxygen- 67 9, 250 Acetylene-oxygen. 50 9, 700

The aforementioned volumes by Jost and by Lewis and Von Elbe list the percentage ranges of composition .to provide detonatable mixtures of air or oxygen with eight different fuels, and describe detonation velocities for a variety of mixtures. With oxygen the lower limit .of acetylene is 3.53.6%, and the upper limit is 9293%.

With air the lower limit of acetylene is 4.2%, and the upper limit is 50%.

The temperature in the detonation wave is high, for several mixtures upwards of 2800 C. However, much of the heat is dissipated before the particles strike a workpiece so that, inherently, little heating of the workpiece results from application of a coating. Heat distortion of the workpiece is thus absent when using the process of the invention. Such heating of the workpiece as may take place can readily be overcome or compensated by interrupting the application of coating from time to time and permitting the workpiece to cool with or without directing a blast of coo-ling fluid such as air against it. External cooling with a liquid spray or fog can also be used, as can internal water cooling when the workpiece is hollow. Particles of a material such as tungsten carbide can be applied securely to a workpiece having a substantially different coeihcient of thermal expansion, such as steel, by cooling the workpiece as described.

The flow rates of the gases may be adjusted so that the mixture just fills the gun in the time interval between igniticns, in which case the detonation front travels to the end of the barrel. At a lower flow rate the detonation front travels through the part of the length of the barrel that contains detonatable gas mixture and a shock wave arising from the detonation travels the rest of the way to the end of the barrel. A greater flow rate of gas gives a flame beyond the end of the barrel.

Although the ignition system illustrated is an adaptation of the conventional system used for internal combustion engines, it is obvious that other ignition means, such as an electrically heated filament or injected hot powder particles, could be used. The illustrated system is convenient, inexpensive, and reliable.

The frequency of the detonations is a factor in attaining effective operation of this detonation gun. The most useful frequency depends on the particular use of the gun, the design of the gun, and the character of the detonating gas mixture. A single detonation suffices when a thin deposit on a small area is desired, for example a tungsten carbide coating .0005 inch thick on a steel surface one inch or less in diameter. For making thicker coatings, and coating larger areas quickly several detonations per second are usually desirable. For instance, fc-r projecting tungsten carbide-cobalt alloy powto form coatings on various tools and articles with a one-inch diameter gun barrel about five feet long using an oxygen-acetylene detonating mixture, a frequency in the neighborhood of 4 per second is very satisfactory and a frequency of 7.8 has been used. For projecting aluminum powder in a similar gun using an air-acetylene detonating mixture, a frequency of 40 per second is very satisfactory and frequencies as high as 70 have been used. At frequencies above 7.8 for the oxygen-acetylene mixture and 70 for the air-acetylene mixture the gun tends to overheat, and flashbacks and continuous burning tend to occur. With better design, the maximum frequency theoretically would be limited only by the mechanics of valve operation or by the rate at which gas could be flowed into the gun between detonations. High rates of gas flow may require inconvenient or dangerous gas pressures, and high rates of operation of the gun may overheat it or some parts of it.

Powders fed into the gun are accelerated to very high velocities. Particles are believed to be accelerated within the gun by one or more of: (a) the shock front at the head of the detonation wave, (b) the rapidly moving gases behind the shock front, and (c) the previously described shock wave beyond (downstream of) the detonated gas mixture.

Powder flow rates into the gun are not particularly critical except as they influence the economics of coating formation, i. e., the cost and rapidity at which a given coating is built up. Ten pounds per hour seems to be most advantageous for good quality of coating with maximum hardness when using 180 cubic feet per hour each of acetylene, oxygen, and nitrogen (for conveying powder and for blanketing the poppet valves) in a oneinch inside diameter gun with a detonation frequency of 4.3 per second. Rates as low as 0.6 pound per hour, and as high as 24 pounds per hour have been used successfully with tungsten carbide powder finer than 44 microns.

One practical application of the invention is to clean or roughen surfaces. For instance a rusty steel plate was effectively cleaned with steel blasting grit of .42 to .59 millimeter particle size. Steel shot can similarly be directed forcibly against a metal body to peen its surface.

Another application is to pulverize frangible material. For example, diatomaceous earth powders of l to micron particle size were passed through the gun, thereby being reduced to 0.1 to 1 micron in size.

Another application of the detonation gun is to the spheroidizing of powders. When unspheroidized powder particles are shot through an oxy-acetylene detonation gun the original sharp corners and edges are melted and rounded over, and in many cases a shape approaching spherical is obtained. Finer particles tend to become more nearly spherical than larger ones, and metals become more spherical than non-metals. Metals which have been successfully spheroidized are chromium, Cr-Ni-B alloy, tungsten, and molybdenum. Non-metals are alumina, boron carbide, silicon carbide, tungsten carbide, silicon nitride, chromium carbide, tungsten carbide-cobalt alloy, titanium carbide, and borosilicate glass. Particle sizes of the powder ranged up to microns in diameter. The composition of the gas mixture detonated in the gun was approximately .5 oxygen, 45.5% acetylene, and 9% nitrogen (the vehicle for carrying powder into the gun). The spheroidized particles may be collected in a liquid or in a wax target.

The invention is particularly well adapted for coating surfaces with any of a wide variety of metals, alloys, metallic compounds, plastics, ceramics, and minerals. Foundation surfaces may be of metal, glass, wood, cloth, paper, plastic, or other. The surface to be coated may be located any convenient small distance from the open end of the gun, say one-half inch to ten inches. For example, an object to be coated with tungsten carbide particles is usually spaced about three inches from the muzzle of the gun.

Good coatings on smooth glass have been made with the gun of the invention, rising aluminum, copper, brass, tin, lead, zinc, and magnesium powders. Copper and zinc have been applied successfully to aluminum; aluminum and nickel to carbon; aluminum to mesh stainless steel wire screen; aluminum and zinc to cotton cloth; aluminum to paper; aluminum, copper, magnesium, nickel, and tin to wood; aluminum to methacrylate plastic;

tin, aluminum, molybdenum, copper, tungsten, tungsten carbide alloy, austenitic stainless steel, chromium, cobaltchromium-tungsten alloy, nickel-molybdenum alloy, boron carbide, and porcelain frit to steel; and tungsten carbide alloy to firebrick. Mixtures of various powders also may be deposited on a workpiece by the detonation gun. For instance a friction plate may be formed by mixing a soft metal powder such as aluminum with a powdered hard material such as alumina, passing the mixture through the gun and depositing the mixture on a steel base as alumina particles in an aluminum matrix. A mixture of iron, chromium, and nickel powders may be deposited on steel to impart resistance to corrosion and wear. It may sometimes be advantageous to include a non-metallic powdered flux with the powder to improve adhesion.

Optimum powder size is believed to be that which permits the surfaces of the particles to be softened enough to give good adherence but does not permit excessive vaporization of the particles. Generally, materials of lower melting point, such as tin, lead, zinc, aluminum, and magnesium may be of larger particle size, say up to microns, and those of higher melting point, such as chromium, tungsten, and tungsten carbide, have been most successfully used when smaller than about 50 microns to produce dense adherent coatings. However, these size limits are not critical, for instance 12 to 32 microns copper powder has been used very successfully to coat aluminum, and tungsten carbide-cobalt alloy powder as coarse as 74 microns has been successfully coated on a metal body.

With aluminum powder smaller than 44 microns, a work surface about two inches from the open end of the one-inch diameter gun, and repeated detonations of air and 10% acetylene at a frequency of about 30 cycles per second, a coating 0.017 inch thick by 1% inch diameter was formed in a minute and a half on a clean steel surface. This coating was substantially impermeable.

Copper or other readily soldered metal may be sprayed onto materials such as glass, porcelain, wood, plastics, or aluminum, which are unsolderable or solderable with difliculty, and the so-coated materials then easily soldered to form a joint.

Pieces of canvas cloth were successfully coated with aluminum and with zinc on both sides by directing the metal particles from the detonation gun against one side only of the cloth. Paper tape was also coated with aluminum while moving the tape slowly in front of the gun muzzle to avoid charring. In both cases the fuel was an air-acetylene mixture.

The method and apparatus of this invention may be used to clean or coat objects submerged in water or other liquid, or protected by a special atmosphere such as argon. The gun operates well under water.

A particularly interesting example of the performance capabilities of this invention is its use to deposit adherent coating of high-melting point abrasion-resistant hard coatings such as tungsten carbide compositions.

Finely powdered (mostly 10 to 40 microns particle size) cast tungsten carbide composition containing, apart from the tungsten, about 9% cobalt and 4% carbon is fed at a rate of about 10 to 15 pounds per hour to a gun of the form shown in Fig. 4 about five feet long and one-inch inside diameter. Acetylene and oxygen are fed in a ratio of about 1 cubic foot of the former to 1 to 2 cubic feet of the latter at an average rate of about 360 cubic feet per hour of the mixture. The average flow of nitrogen is about cubic feet per hour total. The ignition frequency is about four per second. A clean iron or steel surface, either soft or hard (for instance tool steel) preferably roughened as by grit blasting or thinly coated with a soft metal such as copper, nickel, or cobalt, suitably in a coating 0.00025 to 0.0005 inch thick, is p0sitioned about three inches from the open end of the gun. A dense, adherent layer of tungsten carbide composition 0.02 inch thick is deposited at a rate of about one square inch per minute. Thinner or much thicker coatings may be applied by varying the time of application.

Fig. 5 shows at a magnification of 300X the appearance of a tungsten carbide-cobalt alloy coating WC deposited by the process of the invention on a steel base S. The

tungsten carbide included 9% of cobalt. The sample was polished and then given an anodic etch with chromic acid, followed by a potassium permanganate stain.

The detonation gun deposits of tungsten carbide composition are fine grained dense, lamellar structures composed of mixed layers of tungsten carbide (WC), complex carbides of cobalt and tungsten, and small amounts of a secondary tungsten carbide (W2C). These particles which form the coating are elongated and flattened by the heat and impact imparted by the gun into thin overlapping discs or leaves such that their diameter is many times larger than their thickness. This structure is in direct contrast to sintered carbides which have a fine dense equiaxial structure, and tungsten carbide alloy coatings sprayed on with a conventional flame spray gun which have a relatively coarse, porous, weakly bonded structure. The conventional flame spraying method produces a coating of tungsten carbide which is formed of particles that are essentially unchanged in shape and poorly bonded while the detonation gun flattens out the particles and produces an excellent bond between the individual particles.

The coating has bulk density substantially identical with that of the solid cast material applied, 14.5 g./cc. Porosity is less than 1%. Adherence of the coating to the base is excellent, as shown by the fact that portions may be ground down to and through the interface without peeling. The hardness on the Vickers scale is at least 1100. The coating has a smooth matte surface which may be brought to a high polish by standard precision grinding and polishing procedures.

The properties of this coating adapt it for surfaces of such articles as core rods used for pressing and coining, burnishing broaches, snap and plug gages, crusher jaws, shaft seal rings and plates, electrical contacts, boring bars, saw teeth, knife blades, textile thread guides, valve seats and plugs, and bearing surfaces. For some electrical contacts, it may be desirable to incorporate in the powder a metal of high conductivity, such as silver.

This application is in part a continuation of application Serial No. 19,268 and application Serial No. 239,748, both now abandoned.

What is claimed is:

1. A detonation gun comprising a barrel, a mixing chamber communicating with said barrel, means for separately supplying charges of an oxidizing gas and gaseous fuel to said chamber and barrel, an ignition chamber positioned between the barrel and the mixing chamber directly and continuously communicating with said barrel and said mixing chamber, means for entraining powder particles in one of the components of the gaseous mixture formed in the mixing chamber, and means for detonating charges of the mixture repeatedly many times a second, the gun barrel being long enough to allow formation of a detonation wave theerin, whereby a high velocity is imparted to the powder particles.

2. A detonation gun provided with an elongated barrel, a gas mixing chamber at one end of the barrel directly and continuously communicating with said barrel, gas conduits provided with valves for separately supplying an oxidizing gas and a gaseous fuel to said mixing chamber and thence to said barrel, means for supplying powder particles to said barrel, an ignition chamber in the gun having an opening to the barrel of said gun, ignition means in said ignition chamber, the length and diameter of the gun barrel being adapted for the formation and maintenance therein of detonations, whereby powder supplied to said gun is ejected from the barrel under the impetus of said detonations.

3. A detonation gun comprising a barrel of diameter and length to permit the formation in a fluid fuel charge of a detonation; first valve means for supplying successive fluid fuel charges to said barrel; second valve means adjacent said first valve means for supplying an inert gas positioned to flow across said first valve means into said barrel to protect said first valve means; and ignition means for initiating a detonation in said fluid fuel charge in said barrel.

4. A detonation gun in accordance with claim 3, also comprising automatic timing sequence control mechanism operatively associated with said first and second valve means and said ignition means, and acting first to open and then close said first valve means to fill said gun with fluid fuel, then to open said second valve means to start the admission of inert gas to said gun, then to operate said ignition means to initiate a detonation, and after a time delay for such inert gas to purge the gaseous products of combustion from the gun acting to close said second valve means.

5. A method for utilizing detonation waves which comprises providing, in an elongated barrel having an open end, a detonatable body of a detonatable gas and a comminuted solid material unconsumable by the detonation phenomena in said body, and igniting said detonatable body of gas to produce a detonation and thereby to eject said comminuted material at high velocity from the open end of said barrel.

6. A method in accordance with claim 5, wherein said detonatable gas comprises oxygen and a fuel gas selected from the group consisting of acetylene, hydrogen, propane, butane, pentane, and ethylene. 7

7. A method for utilizing detonation waves which comprises mixing a fuel gas and an oxidizing gas to form a mixture capable of being detonated, introducing a detonatable body of said mixture into an elongated barrel having an open end, introducing a comminuted solid material unconsumable by the detonation phenomena in said detonatable body of said mixture, and igniting said detonatable mixture to produce a detonation and thereby transmit to said comminuted material some of the energy from at least one of said detonation and its associated phenomena to eject said comminuted material from the open end of said barrel.

8. A method for utilizing detonation waves which comprises mixing a fuel gas and an oxidizing gas to form a mixture capable of being detonated, introducing a comminuted solid material unconsumable by the detonation phenomena in said detonatable mixture, introducing said detonatable mixture containing said comminuted solid material into an elongated barrel having an open end, and igniting said detonatable body of said mixture to produce a detonation and thereby transmit to said comminuted material some of the energy from at least one of said detonation and its associated phenomena to eject said comminuted material from the open end of said barrel.

9. A method for utilizing detonation waves which comprises mixing a fuel gas containing a comminuted solid material unconsumable by the detonation phenomena with an oxidizing gas to form a mixture capable of being detonated, introducing a detonatable body of said detonatable mixture containing said comminuted material into an elongated barrel having an open end, igniting said detonatable body of said mixture to produce a detonation and thereby transmit to said comminuted material some of the energy of said detonation to eject said comminuted material from the open end of said barrel.

10. A method for utilizing detonation waves which comprises introducing a comminuted solid material unconsumable by the detonation phenomena into an oxidizing gas, mixing said oxidizing gas containing said comminuted material with a fuel gas to form a mixture capable of being detonated, introducing a detonatable body of said detonatable mixture containing said comminuted material into an elongated barrel having an open end, igniting said detonatable body of said mixture to produce a detonation and thereby transmit to said comminuted material some of the energy of said detonation to eject said comminuted material from the open end of said barrel.

11. A method for coating an object which comprises providing, in an elongated barrel having an open end, a detonatable body of a mixture of fuel gas and oxidizing gas capable of being detonated and a comminuted solid material unconsumable by the detonation phenonema; igniting said detonatable body of detonatable mixture to produce a detonation and thereby transmit to said comminuted material some of the energy of said detonation to eject said comminuted material at high velocity from the open end of said barrel; directing said comminuted material toward said object to be coated by virtue of said energy and thereafter repeating said providing, igniting and directing steps at short intervals of time.

12. A method in accordance with claim ll, wherein said comminuted solid material comprises a tungsten carbide composition comminuted to finer than about 50 microns, said fuel gas is acetylene, and said oxidizing gas is oxygen.

13. A method in accordance with claim 11 wherein said mixture of fuel gas and oxidizing gas is an acetyleneair mixture containing between 7% and 13 by volume of acetylene.

14. A method for coating an object which comprises mixing a fuel gas and an oxidizing gas to form a mixture capable of being detonated, feeding a comminuted solid material unconsumable by the detonation phenomena into said detonatable mixture, introducing said detonatable mixture containing said comminuted solid material into an elongated barrel having an open end until said barrel is substantially filled therewith, igniting said detonatable mixture to produce a detonation and thereby transmit to said comminuted material some of the energy of said detonation to eject said comminuted material at high velocity from the open end of said barrel; directing said comminuted material toward said object to be coated by virtue of said energy; and thereafter repeating said mixing, feeding, introducing, igniting and directing steps at short intervals of time less than one second.

15. A method in accordance with claim 11 which also comprises passing a body of an inert gas through said barrel between said providing and subsequent ignition steps.

16. A method for coating an object which comprises mixing a fuel gas and an oxidizing gas to form a mixture capable of being detonated, introducing said detonatable mixture into an elongated barrel having an open end until said barrel is substantially filled therewith, feeding a comminuted solid material unconsumable by the detonation phenomena into said detonatable mixture, igniting said detonatable mixture to produce a detonation and thereby transmit to said comminuted material some of the energy of said detonation to eject said comminuted material at high velocity from the open end of said barrel, directing said comminuted material toward said object to be coated under the impetus of said energy and thereafter repeating said mixing, introducing, feeding, igniting and directing steps at short intervals of time less than one second.

17. A method in accordance with claim 16 which also comprises passing an inert gas through said barrel between said ignition and said subsequent introducing steps.

18. A method for coating an object which comprises mixing a fuel gas with an oxidizing gas to form a mixture capable of being detonated; prior to such mixing feeding into at least one of the fuel gas and oxidizing gas a comminuted solid material unconsumable by the detonation phenonema; introducing said detonatable mixture containing said comminuted material into an elongated barrel having an open end until said barrel is substantially filled therewith; igniting said detonatable mixture to produce a detonation and thereby transmit to said comminuted material some of the energy of said detonation to eject said comminuted material at high velocity from the open end of said barrel; directing said comminuted material toward said object to be coated under the impetus of said energy; and thereafter repeating said feeding, mixing, introducing, igniting and directing steps at short intervals of time less than one second.

19. A method in accordance with claim 18, which also comprises passing an inert gas through said barrel between said ignition and said subsequent introducing steps.

20. A method of preparing for soldering surfaces of objects which are diflicult to solder directly, which comprises applying a readily solderable metal onto the surfaces to be soldered in accordance with the method of claim 11, thereby providing a thin adherent coating of solderable metal on such surfaces.

21. A detonation gun comprising an elongated barrel having an open end, said barrel having a length-to-diameter ratio sufliciently high to permit the formation of a detonation therein; mixing chamber means directly and continuously communicating with said barrel for forming and passing to said barrel charges of detonatable fluid fuel mixture; means for supplying the components of said detonatable fluid fuel mixture to said mixing chamber means; supply means associated with said barrel for providing comminuted solid material in said detonatable fluid fuel mixture; and means associated with said barrel for igniting said fluid fuel mixture in said barrel to initiate 1 3 said detonation and propel said comminuted solid material from said gun.

22. A detonation gun comprising an elongated barrel having an open end, said barrel having a length'to-diameter ratio sufiiciently high to permit the formation of detonations therein; means associated with said barrel for providing successive quantities of a detonatable fluid fuel mixture in said barrel at regular intervals; supply means associated with said barrel for providing comminuted solid material in each successive quantity of detonatable fluid fuel mixture; and means directly and continuously communicating with said barre] for igniting, at timed intervals, each of said successive quantities of fluid fuel mixture in said barrel to initiate a series of detonations and propel said comminuted solid material from said gun.

23. A detonation gun employing detonations comprising an elongated barrel open at one end and having an ignition chamber directly and continuously communicating with the end thereof, said barrel having a length-todiameter ratio sutficiently high to permit the formation of a detonation therein; means associated with said chamher for providing a detonatable fluid fuel mixture in said barrel and ignition chamber; supply means associated with said chamber for providing a comminuted solid material in said detonatable fluid fuel mixture; and means, associated with said ignition chamber, for igniting said fluid fuel charge in said chamber and barrel to initiate said detonation and propel said comminuted solid material from said gun.

24. A detonation gun employing detonations comprising an elongated barrel open at one end and having an ignition chamber directly and continuously communicating with the end thereof, said barrel having a length-todiameter ratio sufficiently high to permit the formation of detonation therein; means associated with said chamber for providing successive quantities of a detonatable fluid fuel mixture in said chamber and barrel at intervals; supply means associated with said chamber for providing comminuted solid material in each successive quantity of fluid fuel mixture; and means associated with said ignition chamber for igniting, at automatically timed intervals, each of said successive quantities of fluid fuel mixture in said chamber and barrel to initiate a series of detonations and propel said comminuted solid material from said gun.

25. A method of cleaning or roughening surfaces of a workpiece utilizing detonations and their associated phenomena which comprises providing, in an elongated barrel having an open end, a detonatable body of a detonatable gas containing a comminuted solid material unconsumable by the detonation phenomena in said body; igniting said detonatable body of gas to produce a detonation and its associated phenomena and thereby eject said comminuted solid material at high velocity from the open end of said barrel; and directing said comminuted solid material toward said workpiece surface to roughen or clean said surface.

26. A method of pulverizin g frangible material utilizing detonations and their associated phenomena which comprises providing, in an elongated barrel having an open end, a detonatable body of detonatable gas containing a frangible solid material unconsumable by the detonation phenomena in said body; igniting said detonatable body of gas to produce a detonation and its associated phenomena and thereby pulverize said frangible material and eject it from the open end of said barrel; and collecting said pulverized frangible material after ejection from said barrel.

27. A method of spheroidizing material utilizing detonations and their associated phenomena which comprises providing, in an elongated barrel having an open end, a detonatable body of a detonatable gas containing a fusible, comminuted solid material unconsumable by the detonation phenomena in said body; igniting said detonatable body of gas to produce a detonation and its asso- 2,714,563 1 l 1 2 ciated phenomena and thereby fuse said comminuted solid FOREIGN PATENTS material and eject it at high velocity from said open end G t B f 1943 of said barrel, whereby said material is spheroidized; and Tea n am n o collecting said spheroidized material after ejection from OTHER REFERENCES Third Symposium on Combustion and Flame and Exsaid barrel. 5

plosion Phenomenon, Williams & Wilkins, Baltimore, Maryland 1949, pgs. 185-190.

Jost Explosion and Combustion Processes In Gas, 1946,

References Cited in the file of this patent UNITED STATES PATENTS 1,375,653 McLain et al. Apr. 19, 1921 10 1,620,994 Berstamante Mar. 15, 1927 2,374,816 Hansen May 1, 1945

Claims (1)

18. A METHOD FOR COATING AN OBJECT WHICH COMPRISES MIXING A FUEL GAS WITH AN OXIDIZING GAS TO FORM A MIXTURE CAPABLE OF BEING DETONATED; PRIOR TO SUCH MIXING FEEDING INTO AT LEAST ONE OF THE FUEL GAS AND OXIDIZING GAS A COMMINUTED SOLID MATERIAL UNCONSUMABLE BY THE DETONATION PHENONEMA; INTRODUCING SAID DETONATABLE MIXTURE CONTAINING SAID COMMINUTED MATERIAL INTO AN ELONGATED BARREL HAVING AN OPEN END UNTIL SAID BARREL IS SUBSTANTIALLY FILLED THEREWITH; IGNITING SAID DETONATABLE MIXTURE TO PRODUCE A DETONATION AND THEREBY TRANSMIT TO SAID COMMINUTED MATERIAL SOME OF THE ENERGY OF SAID DETONATION TO EJECT SAID COMMINUTED MATERIAL AT HIGH VELOCITY FROM THE OPEN END OF SAID BARREL; DIRECTING SAID COMMINUTED MATERIAL TOWARD SAID OBJECT TO BE COATED UNDER THE IMPETUS OF SAID ENERGY; AND THEREAFTER REPEATING SAID FEEDING, MIXING, INTRODUCING, IGNITING AND DIRECTING STEPS AT SHORT INTERVALS OF TIME LESS THAN ONE SECOND.

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