Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/0006—Spraying by means of explosions

Definitions

• This invention is applicable in the area of thermal projection technologies for the production of coatings and, in particular, in detonation projection technologies.
• the object of the present invention is to provide a powder injection device that, incorporated in a detonation device, allows to increase its precision, reliability, versatility and productivity.
• detonation projection technology is mainly used for the application of coatings to parts that are exposed to severe conditions of wear, heat or corrosion and is based primarily on the use of kinetic energy produced by the detonation of a mixture of combustible gases to deposit a powder of coating material on the piece.
• the coating materials commonly used in detonation processes include metallic, ceramic-metallic, ceramic powders, etc. and are applicable to improve resistance to wear, erosion, corrosion, as thermal insulators and as insulators or electrical conductors .
• the detonation projection is done by projection guns basically composed of a tubular detonation chamber, with a closed and an open end to which a tubular barrel is also attached.
• the combustion gases are injected inside the detonation chamber and through a spark plug the ignition of the gas mixture that causes a detonation takes place and as a consequence a shock wave or pressure that propagates, at supersonic speeds, by the inside of the chamber and then through the inside of the barrel until it comes out of the open end of it.
• the coating material powder is generally injected into the barrel just before the propagation front of the pressure wave arrives and consequently is dragged by this wave to the end of the barrel by depositing on a substrate or piece arranged in front of said barrel. This impact of the coating powder on a substrate produces a high density coating that has very large adhesive characteristics.
• This process is repeated cyclically until the part is adequately coated.
• powder feeders provide continuous feeding, so they are suitable in high-speed or plasma projection technologies, but are not applicable for use in detonation projection technologies since detonation is a discontinuous process that requires therefore a discontinuous feed of powder.
• the feeders used in detonation equipment provide a discontinuous feed by means of devices that control the amount of dust supplied to the detonation gun in each explosion but they are always devices specially designed for each type of gun, that is, they are not interchangeable for use with other guns or on other machines that require powder feeding. According to the dust measurement mechanism used, they can be classified into two categories:
• These devices have as a common feature that they incorporate a volume or reservoir in which a limited amount of dust is stored that, by gravity, feeds another volume or dosing chamber that by pushing a gas feeds the detonation cannon.
• These systems have as disadvantage their lack of precision in the amount of powder dosed, mainly due to their difficulty in keeping the volume and / or pressure conditions of the feeder tank stable for long periods of projection. This is so, since part of the detonation wave that pressurizes the deposit enters the dust feeder tank so that the dust falls by gravity and by the effect of the pressure at each moment in the tank.
• the feeding of the tank to the dosing chamber is produced by gravity, when the detonation gun, usually manipulated by an industrial robot, occupies positions in which the dust container is not vertical, the powder does not fall to the dosing chamber continuously and therefore it is difficult to guarantee a constant feed.
• the present invention resolves the above-mentioned inconveniences to a complete satisfaction by means of an injection system that allows the use of a continuous powder feeder, of the conventional type, for the feeding of a detonation projection system, the powder injection being performed cyclically, synchronized with the firing frequency of the cannon and with 5 high precision in powder dosing.
• the recommended system allows the gun and the continuous powder feeder to be connected directly, and is composed of a dosing chamber that receives continuous powder feed, and a conduit that directly communicates the chamber with the gun barrel of such so that, at each detonation cycle, the detonation pressure wave reaches the dosing chamber momentarily interrupting the feed so that the subsequent suction of the detonation wave drags the dust contained in the dosing chamber by injecting it into the barrel of the gun.
• the dosing chamber communicates with the gun barrel through a direct tubular duct, of reduced diameter, such that the pressure wave that progresses through the barrel passes to the communication duct and when the chamber is reached doser undergoes a sharp expansion that fills the chamber with pressurized gas plugging the inlet of the powder feed line.
• a direct tubular duct of reduced diameter
• the sudden expansion of the gas in the dosing chamber generates a turbulence that produces the fluidization of all the dust contained in the dosing chamber in such a way that the suction process that follows the detonation drags all the dust contained in the chamber so It is possible to control exactly the amount of dust injected into the barrel.
• the pressure wave is composed of hot gases produced in the combustion process the interaction of these gases with the powder contained in the dosing chamber produces a preheating of the powder that favors its fluidization.
• the low pressure generated after the detonation wave produces a suction that drags the gas contained in the dosing chamber and the powder that was fluidized.
• the entrained dust reaches the canyon where it remains until the pressure wave produced in a new detonation cycle drags it by depositing it on the surface of the piece to be coated.
• the detonation pressure wave itself performs the injection of dust into the barrel in a cyclic manner and synchronized with the firing frequency of the cannon, thus transforming a continuous feed of dust into an injection pulsed into the barrel of the gun without using complex mechanical devices.
• the expansion constituted by the dosing chamber reduces the speed of the pressure wave preventing it from eroding the dosing chamber and progressing towards the powder feeder eliminating the risk of the pressure wave causing irreparable damage to the feeding system. .
• the dosing chamber has an extension or auxiliary chamber, facing the communication channel with the detonation barrel, which aims to increase the length of the dosing chamber, to reduce the impact force and consequently the effects of erosion produced for him shock of gases and dust on this area of the dosing chamber.
• FIG. 1 Schematically shows the powder injection device object of the invention.
• Figure 2 shows a sequence of operation of the powder feeding device of the invention.
• Figure 3. Shows a graph in which the evolution of the pressure at the point of powder injection is represented, over two firing cycles of the detonation gun. 8
• Figure 4. Schematically shows an embodiment with a double powder injection device.
• the system of the invention constitutes a connection device between a continuous feeding system and a detonation gun and is mainly composed of an expansion and dosing chamber (2) which is accessed through of a direct conduit (5), the powder supplied by a continuous feeding system (7), not shown, it being provided that the dosing chamber (2) also communicates with the barrel (1) through a direct conduit ( 4) .
• the dosing chamber (2) is essentially an expansion chamber, which communicates with the barrel (1) of the gun through a direct tubular conduit (4), of reduced diameter, such that the pressure wave that It progresses through the barrel (1) passes to the communication duct (4) and reaches the dosing chamber (2).
• the detonation gases that reach the dosing chamber (2) undergo an abrupt expansion that fills the chamber with pressurized gas by plugging the inlet of the dust supply line (5). In this way, it is possible to cyclically interrupt the powder feeding from the continuous feeder (7) and therefore, it is possible to control the amount of powder dosed in the chamber and consequently the amount of dust that will be injected into the barrel in each cycle of detonation.
• the sudden expansion of the gas in the dosing chamber (2) generates a turbulence that produces the fluidization of all the powder contained in the dosing chamber (2) in such a way that the suction that follows the detonation will drag all the dust contained in the chamber by injecting it into the barrel (1).
• the fluidization of the powder contained in the dosing chamber (2) is favored by the fact that the detonation wave gases are at a high temperature.
• the low pressure generated after the detonation wave produces a suction that drags the gas contained in the chamber (2) and dust included in it that was completely fluidized.
• the entrained dust reaches the barrel (1) where it remains until the pressure wave produced in a new detonation cycle drags it by depositing it on the substrate (3) or piece to be coated.
• the expansion of the detonation wave gases inside the chamber (2) causes a reduction in its speed, which minimizes the erosive effect on the walls of the dosing chamber (2) and prevents the Pressure wave advances through the duct (5) to the powder feed system (7).
• the expansion chamber (2) reduces the speed of the pressure wave, it is inevitable that there will be a collision of the gases against the inner wall of the chamber, in the area facing the communication conduit (4) of such that the collision of the pressurized gas with the fluidized powder against this area would inevitably cause strong erosions.
• the dosing chamber incorporates an extension or auxiliary chamber (6) whose inlet is facing the communication conduit (4) so that the pressure wave jet expands inside the Dosing chamber (2) and inside the extension (6) 10 avoiding the sharp collision of the jet against the chamber wall (2).
• the expansion chamber (2) can be of any size and shape as long as the gases that access it through the conduit (4) undergo an abrupt expansion upon entering the chamber.
• the communication conduit (4) can also have any length or diameter as long as the diameter is large enough to prevent dust from adhering to its walls by plugging it and such that the detonation wave pressure that progresses through it does not is excessively large or what is the same, such that the pressure allows the fluidization of the dust contained in the chamber but does not put the danger of the continuous system of powder feeding or compromise the energy available for detonation.
• FIG. 3 A graph illustrating the variations in pressure over time at the point of dust injection has been shown in Figure 3, with a peak or sudden rise in pressure (D) corresponding to the detonation being clearly observed, followed by a pressure drop (S), corresponding to the suction that follows the detonation, to then remain more or less constant until a new pressure peak (D) occurs in the next detonation cycle followed by the subsequent suction (S ).
• D peak or sudden rise in pressure
• S corresponding to the suction that follows the detonation
• a continuous powder feed system (7) supplies powder to the dosing chamber (2) through a conduit (5). Is 11 feed is produced continuously and directly without valves or closing devices between the powder feed system (7) and the dosing chamber (2).
• the sharp expansion of the gases generates a turbulence that causes the fluidization of all the powder contained in the dosing chamber (2), this fluidization being favored by the high temperature at which the detonation gases are found.
• the low pressure (S) causes a suction that draws the gases contained in both the dosing chamber (2) as in the duct (4) and therefore also of the powder contained in the dosing chamber (2).
• the dust enters the cannon, waiting for the next pressure front (D) to arrive, corresponding to the next detonation, which will drag it in its path.
• the suction generated by the pressure wave drags all the dust contained in the dosing chamber (2), thus achieving that the injection of dust into the barrel is 12 Perform periodically and controlled.

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• Nozzles (AREA)
• Coating By Spraying Or Casting (AREA)

Priority Applications (11)

Applications Claiming Priority (1)

Publications (1)

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ID=8302330

Family Applications (1)

Country Status (11)

Cited By (3)

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Citations (5)

Family Cites Families (4)

• 1998
  • 1998-01-23 AT AT98900545T patent/ATE491524T1/de not_active IP Right Cessation
  • 1998-01-23 US US09/600,940 patent/US6398124B1/en not_active Expired - Lifetime
  • 1998-01-23 EP EP98900545A patent/EP1052024B1/en not_active Expired - Lifetime
  • 1998-01-23 WO PCT/ES1998/000015 patent/WO1999037406A1/es not_active Ceased
  • 1998-01-23 CA CA002325021A patent/CA2325021C/en not_active Expired - Fee Related
  • 1998-01-23 RU RU2000122154/12A patent/RU2198037C2/ru not_active IP Right Cessation
  • 1998-01-23 BR BR9814786-2A patent/BR9814786A/pt not_active IP Right Cessation
  • 1998-01-23 JP JP2000528374A patent/JP4022370B2/ja not_active Expired - Fee Related
  • 1998-01-23 DE DE69842054T patent/DE69842054D1/de not_active Expired - Lifetime
  • 1998-01-23 ES ES98900545T patent/ES2374460T3/es not_active Expired - Lifetime
  • 1998-01-23 AU AU55619/98A patent/AU761428B2/en not_active Ceased

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