Fluid sprinkling – spraying – and diffusing – With means fusing solid spray material at discharge means – With supply holder for fusible material
Reexamination Certificate
2002-04-23
2004-06-08
Ganey, Steven J. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
With means fusing solid spray material at discharge means
With supply holder for fusible material
C239S079000, C239S081000, C239S400000, C239S419300, C239S427000, C239S433000
Reexamination Certificate
active
06745951
ABSTRACT:
OBJECT OF THE INVENTION
This invention refers to a spray gun, of the type used in the industrial thermal spray area for obtaining coatings, especially in detonation spray technologies.
The object of the invention is to achieve a new detonation gun with greater productivity than existing ones, maintaining stable and continued optimum spray conditions in each firing cycle. In relation to previous detonation devices, this gun allows the firing frequency to be increased, together with the amount of powder and feeder gases and in consequence, the amount of coating powder deposited per unit of time, maintaining optimum levels of quality that are characteristic of coating produced by detonation technologies.
For this purpose, a new gas feeding system is proposed, in a new explosion chamber, that permits the gun's operating frequency to be increased, making it possible to maintain the optimized characteristics of each explosion stable and constant, even at high frequencies and a new system for feeding products in the barrel that allows the distributed injection of products to any point within the barrel achieving an increase of the amount of powder injected into the barrel and reducing the limitations associated with obstruction of feeder ducts, together with great operating versatility by being able to select the injection point.
The barrel feeding system, in addition to the coating powder, it is also useful to introduce other products that can condition the thermal spray process, in this way permitting great flexibility when modifying the operating parameters, by being able to modify the characteristics of the generated explosions and to improve and optimize the coatings obtained in this way.
It is also an object of the invention to achieve better performance from the gun, based on thermally isolating the gases produced in the explosive process with respect to the cooled barrel wall, in order to obtain better use of the energy that is carried by these gases, with the resulting increase in the gun's performance and its efficiency.
BACKGROUND TO THE INVENTION
Current detonation spray technologies are mainly used for the application of coatings to parts that are subject to severe conditions of wear, heat or corrosion, and which are fundamentally based on the use of the thermal and kinetic energy produced by the explosion of a gaseous mixture to deposit a coating material powder on these parts.
The coating materials that are usually employed in detonation spray processes include metallic powder, metal-ceramics and ceramics etc, and are applied to improve the resistance to wear, erosion, corrosion and as thermal insulators or as electrical insulators or conductors, among other applications as given in the literature.
Detonation spray is performed with spray guns that basically consist of a tubular explosion chamber with one end closed and the other open, to which a barrel, also tubular, is connected. The explosive gases are injected inside the explosion chamber and ignition of the gas mixture is produced by means of a spark plug, which provokes an explosion and in consequence, a shock or pressure wave that reaches supersonic speeds during its propagation inside the barrel until it leaves the open end.
The coating material powders are usually injected inside the barrel in contact with the explosive mixture so that they are dragged along by the propagating shock wave and by the set of gaseous products from the explosion, which are expulsed at the end of the barrel, and deposited on a substrate or part that has been placed in front of the barrel. This impact of the coating powders on the substrate produces a high density coating with elevated levels of internal cohesion and adherence to the substrate. This process is repeated in a cyclic manner until the part is suitably coated.
In traditional detonation spray equipment, the gases used in the generation of the explosive process are mixed in a separate chamber prior to the explosion chamber, which is then fed by a homogeneous mixture of gases in each explosive cycle. Traditionally, this pre-mixing chamber is isolated from the explosion chamber during the explosive phase for safety reasons, through the use of valves in one or more gas lines, with and without the introduction of an inert gas between two consecutive explosions.
In other, more advanced types of detonation equipment, presented by the applicant in PCT US96/20160, this isolation between the pre-mix and explosion chambers is achieved by using dynamic valves, which means they do not have any moving parts, which overcomes the inherent disadvantages of the previously-mentioned mechanical systems. However, these devices continue to employ a pre-mixing chamber in order to homogenize the gas composition that feeds the explosion chamber.
Recently, the same applicant developed a type of detonation spray equipment, described in PCT ES97/000223, with a gas injection system that does not employ mechanical valves or systems to shut off the gas supply, and, in addition, allows the gases feeding to be fed directly and separately to the explosion chamber through a series of independent passageways, where each passageway is made up of an expansion chamber and a large number of distributor ducts with reduced cross section and/or long length. This results in a system without any moving mechanical parts and/or pre-mixing chamber. In this device, the expansion chamber for each passageway is in direct communication with the corresponding supply line, while the distributor ducts are suitably arranged so that multiple gas injection points open out on the internal surface of the explosion chamber, producing a continuous and separate feeding at multiple points, which guarantees that the combustible mixture is produced directly and in a homogeneous manner, throughout the entire explosion chamber prior to each ignition and with sufficient flow to fill the chamber in each detonation cycle.
In turn, in the application PCT ES98/00015, also of the same applicant, a powder injection system is described for a detonation spray gun consisting of a dosing chamber directly fed by a conventional type continuous powder feeder that communicates with the barrel by means of a direct duct. In this way, the pressure generated by the explosion and which advances along the barrel, passes through the communication duct and undergoes a brusque expansion on reaching the dosing chamber, which interrupts the powder feeding from the continuous feeder and produces complete fluidization of the powder in the dosing chamber. The fluidized powder is carried by the suction towards the barrel, where the pressure wave generated in a new explosive cycle drags it out and deposits it on the surface to be coated.
The detonation guns of the described type produce coatings of excellent quality, but they have a limitation in so far as the amount of powder that can be deposited per unit of time. This is due to the fact that, for a detonation gun of a determined size, the optimum amount of powder that can be processed during each explosion is limited by the existence of a maximum volume of optimized gaseous mixture that may be processed in each explosion and capable of generating proper characteristics of the actual explosive process itself. An increase in the gaseous volumes involved in each explosion on this maximum volume of optimized mixture is not directly translated into an improvement of the explosive process of each cycle, so that an increase in the amount of powder deposited per unit of time should not be obtained so much because of an increase in the powder processed in each explosion, but as a consequence of the increasing in the firing frequency, guaranteeing optimum explosive characteristics of each cycle in all cases.
On the other hand, the repetition of the explosive cycle at high frequencies and generating explosions with characteristics equivalent to those obtained at lower frequencies also requires higher gas flows in order to guarantee constant gas volumes involved in each explosion. The application of these increments i
Barykin Georgy Yur'evich
Fagoaga Altuna Iñaki
Aerostar Coatings, S.L.
Ganey Steven J.
Katten Muchin Zavis & Rosenman
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