Patent Grant
9095863
Not Applicable
Not Applicable
This invention relates to the formation of fusible coatings or structures (e.g., polymer or polymer composite coatings, or reinforced polymer coatings, as well as polymer, or reinforced polymer structures) via a thermal spray process. In particular, the invention relates to formation of these coatings or structures using a flameless thermal spray process.
The background art is characterized by U.S. Pat. Nos. 3,801,020; 3,958,758; 4,416,421; 4,694,990; 5,236,327; 5,285,967; 5,503,872; 5,932,293 and 7,216,814; by U.S. Patent Applications Nos. US2006/166153 and US2009/095823; and by International Patent Application No. PCT/US2007/009021; the disclosures of which patents and patent applications are incorporated by reference as if fully set forth herein.
As used herein, the following terms and variations thereof have the meanings given below, unless a different meaning is clearly intended by the context in which such term is used.
“A,” “an” and “the” and similar referents used herein are to be construed to cover both the singular and the plural unless their usage in context indicates otherwise.
“About,” “approximately,” and “in the neighborhood of” mean within ten percent of a recited parameter or measurement, and preferably within five percent of such parameter or measurement.
“Comprise” and variations of the term, such as “comprising” and “comprises,” as well as “having” and “including” are not intended to exclude other additives, components, integers or steps.
“Exemplary,” “illustrative,” and “preferred” mean “another.”
In illustrative embodiments, the present invention is an improvement of embodiments of the invention described in the above related regular U.S. patent application. In these embodiments, the present invention comprises features to improve its usability, including an electronic ignition system, a single air supply manifold system, and an air shielded powder feed tube. These new features render the present invention easier to handle and easier to operate.
In illustrative embodiments of the present invention, an electronic ignition system allows the operator to light the flame with the touch of a button. In earlier embodiments, the operator ignited the burner using a butane torch or a welding spark striker. The electronic igniter makes it much easier for the operator to light the applicator. Electronic igniters are common in fixed applications such as gas hot water heaters, furnaces, and other home appliances. For these applications, low velocity gas streams are ignited using high voltage sparks ranging from 10 kilovolt (kV) to 15 kV. For the present invention, the gas velocities are too high for a conventional spark igniter. With illustrative embodiments of the present invention, a novel pilot tube electrode is used to create a region of low velocity gas to enable burner ignition at all applicator gas flow settings.
To generate the continuous 10 kV to 15 kV spark at the applicator required an additional novel technology. Spark generators using high turn ratio transformers and autotransformers are commonly found in home appliances and automobiles. These spark igniters are much too large to mount directly on the applicator of the present invention. The other commonly used alternative is to mount the spark igniter remotely and run a high voltage cable through the applicator umbilical. These cables are heavy and can over time leak high voltage, which could shock and startle the operator. For this application, a small high turn transformer, capacitor, and novel spark generation circuit were developed that only requires low voltage power. The power is supplied through the umbilical using a lightweight wire.
The applicator described in the above cross-referenced patent application and other thermal spray systems like the Xiom thermal spray system (Xiom Corp., West Babylon, New York) utilize multiple individually controlled air lines to provide the correct mix of air and fuel to get correct combustion and polymer melt conditions. These systems have numerous controls which make establishing applicator process conditions very difficult for the operator. Also, these multiple discrete air lines result in a large bundle of tubes running from a control cart to the applicator through an umbilical. These tube bundles make the umbilical very stiff and heavy. In preferred embodiments, the present invention uses a single air input line, which is split into various air streams and balanced at the applicator through a factory pre-adjusted manifold system that sets the correct air balance.
In an illustrative embodiment of the present invention, an air shielded powder feed tube allows the polymer to be sprayed without fouling the applicator. Earlier prototypes of the applicator, which did not have this feature, became fouled with polymer after extended use. The development of the air shielded feed tube allowed the applicants for patent to move the spray nozzle toward the outlet of the applicator shroud, which eliminated the fouling problem. In addition to this benefit, the shielded air feed tube produces a spray pattern superior to the unshielded design. The shielding air causes the polymer air stream in the feed tube to contract—just downstream of the feed tube exit—and then expand. This contraction and expansion results in an optimum spray pattern with very even powder distribution on the substrate.
In an illustrative embodiment, the invention comprises a thermal spray system for depositing a polymer, a polymer composite coating, or a structure onto a target substrate. In this embodiment, a stream of air is heated by a flame in a defined combustion zone, preferably using the Resodyn PTS-30 System (available from Resodyn Engineered Polymeric Systems of Butte, Mont.). In a preferred embodiment of the present invention, an igniter electrode assembly utilizes a nickel wire or another wire that is capable of withstanding a high temperature for the electrode. The wire has a nominal size of 12 American Wire Gauge (AWG). Nickel has a melting temperature of 1500° C. which is sufficient to withstand the heat at the face of the burner. In this embodiment, the electrode is installed in an electrode insulator which is made from a tube of alumina ceramic, such as Coorstek AD-998 (from Coorstek of Golden, Colo.), which has a dielectric strength of 220 Volts per millimeter. The electrode insulator preferably has a nominal outside diameter of 3/16 inch and a nominal inside diameter of 3/32 inch. The electrode insulator fits inside the electrode tube which as a nominal inside diameter of ¼ inch. The clearance between the inside of the electrode tube and the electrode insulator creates a 1/32 inch thick annular flow passage for the pilot propane gas and air mixture.
In this embodiment, the flow rate of the propane gas and air mixture that flows into the electrode tube is controlled by two 3/32 inch diameter electrode inlet hole(s). The hydraulic diameter of these inlet holes is significantly smaller than the hydraulic diameter of the annular flow passage between the inside diameter of the electrode tube and the electrode insulator. The electrode assembly is preferably optimized to create a pilot which has sufficient propane gas and air flow rate to ignite while keeping the pilot velocity low enough so that the spark ignites the pilot without blowing the spark out.
Several of the components in the illustrative igniter circuit described herein are common components which are known to those trained in the art. For example, the microcontroller used in this circuit is a CY8C24123A-24SXI manufactured by Cypress Semiconductor of San Jose, Calif., but any suitable microcontroller could be used. The STMicroelectronics FLC-200B U2 Fire Lighter Circuit thyristor type integrated circuit (from STMicroelectronics of Geneva, Switzerland) is designed to trigger using a 220 Volt alternating current (AC) signal, which is fundamental to this architecture. For this circuit, the charge capacitor must be sufficiently large to store enough energy to create a sufficiently strong spark. For this illustrative embodiment, the capacitor value used is 1 microfarad (μF). The spark transformer is a very high turn ratio transformer with an inductance ratio of 25:1. The transformer has a very high Q and a resonant frequency of 38.3 kHz. At that resonant frequency, the voltage ratio is 30:1. When the FLC-200B U2 Fire Lighter Circuit fires, a very high current pulse is induced in the spark transformer. Simply multiplying the 200V charge when by the voltage ratio of the spark transformer results in a 6 kV spike. The actual voltage is much higher because the capacitor and primary winding of spark transformer discharges very quickly. The primary winding of the spark transformer is an inductive load. The voltage across an inductive load is equal to the inductance multiplied by the rate of change of current over time.
In an illustrative embodiment, a single air supply system employs air flow amplifiers, manifolds, and flow restrictors to achieve the correct balance of air flow rates for all air streams. In this embodiment, non-coanda air amplifiers, like those disclosed in U.S. Pat. No. 4,046,492 assigned to Vortec Corporation of Cincinnati Ohio, are used. Preferably, all of the air amplifiers used achieve an air amplification ratio of nominally 10:1.
In an illustrative embodiment, the system air balance is achieved by first sizing and tuning the air amplifier for the combustion gas and air stream with the applicator being designed to operate in a power range from 15 kW to 30 kW. In this embodiment, the output power is directly proportional to the volume of propane gas metered into the applicator through the propane nozzle. With complete stoichiometric combustion of propane, the combustion energy released is 43.9 kilowatts per standard cubic feet per minute (kW/scfm). So, to achieve 15 kW-30 kW requires 0.34-0.68 scfm of propane gas. For complete stoichiometric burning, the ratio of air to propane is 25:1, so the air introduced into the combustion gas and air stream is 8.5 scfm to 17 scfm. The air amplifier for the combustion and air stream is preferably tuned to generate 8.5 scfm to 17 scfm of air to assure that a stoichiometric mixture of air and gas is fed into the heater assembly for complete combustion.
In an illustrative embodiment, the upper air amplifier air input stream is controlled by sizing the upper air amplifier air restrictor, which for the present invention has a nominal inside diameter of 3/16 inch. With this embodiment, the upper air amplifier air input stream is routed first to the air amplifier that draws in the diverter air inlet stream. A portion of the upper air amplifier air input stream flows past the diverter air amplifier venturi and creates the air stream diverter air amplifier high velocity air stream. The remaining portion of the upper air amplifier air input stream flows through two cooling air restrictor(s) and creates the cooling air amplifier high velocity air stream.
In this embodiment, the total volume flow rate of the upper air amplifier air input stream is 6 scfm to 12 scfm for power levels of 15 kW to 30 kW. Sixty percent of this total upper air amplifier air input stream exits through the diverter air amplifier high velocity air stream. The remaining 40 percent exits through the cooling air amplifier high velocity air stream.
In an illustrative embodiment, the shielded air feed tube assembly is comprised of two concentric tubes: the inner powder feed tube and the outer shielding air tube. Shielding air is forced through the annular space between these two tubes. The shielding air stream serves two purposes. First, it creates a high velocity air steam around the powder feed outlet stream. This air steam creates a barrier that prevents the particles from drifting backwards and fouling the applicator. Second, the shielding air stream forces the powder feed output stream to converge and then expand downstream of the powder feed tube distal tip. The applicants have found that this expansion and contraction creates a well disbursed, uniform coating spray pattern.
In an illustrative embodiment, the invention is a thermal spray gun comprising: a lower air manifold assembly that is operative to receive a propane input stream and a main air input stream, to divide said main air input stream into a combustion air amplifier air input stream and an upper air amplifier air input stream and, to combine said propane input stream with said combustion air amplifier air input stream to produce a combustion gas and air stream; a heater assembly that is operative to receive said combustion gas and air stream, said heater assembly comprising a perforated heater plate and a diverter cone; an igniter that is operative to ignite said combustion gas and air stream to produce a flame on said perforated heater plate, said igniter comprising an electrode tip; an upper air manifold assembly that is operative to receive said upper air amplifier air input stream and to produce a diverter air amplifier high velocity air stream and a cooling air amplifier high velocity air stream, said diverter air amplifier high velocity air stream being operative to draw a diverter air inlet stream into said upper air manifold assembly to produce an inner diverter outlet steam and an outer diverter outlet stream, and said cooling air amplifier high velocity air stream acting to draw a cooling air inlet stream into said upper air manifold assembly to produce a cooling air outlet stream; and a feed tube assembly that is operative to receive a powder feed input stream and to produce a powder feed outlet stream, said feed tube assembly comprising a feed tube tip; wherein said inner diverter outlet stream is operative to cool said feed tube tip and said diverter cone and to surround said powder feed outlet stream; and wherein said outer diverter outlet stream is operative to urge said flame radially outward. In another embodiment, said lower air manifold assembly is further operative to divide said main air input stream into said combustion air amplifier air input stream, said upper air amplifier air input stream, and a shielding air inlet stream; and said feed tube assembly is further operative to receive said shielding air inlet stream and to produce a shielding air inlet stream that is operative to cause said powder feed outlet stream to contract to produce a powder contraction zone and then to expand to produce a powder expansion zone. In another embodiment, said igniter further comprises a conductive electrode tube having and electrode inlet hole and an annular void, an electrode insulator and an electrode, said electrode being separated from said electrode tube by said electrode insulator. In another embodiment, said electrode inlet hole and an annular void receive a portion of said combustion gas and air stream and produce a pilot gas air mixture stream that is ignitable by a spark traveling across a spark gap between said tip electrode and said electrode tube.
In another illustrative embodiment, the thermal spray gun further comprises: an electronic ignition circuit comprising: a step-up transformer, a normally-open relay, an igniter switch, a micro-controller that energizes said normally-open relay when said igniter switch is closed, a capacitor, a spark transformer, and a fire starter integrated circuit; wherein, when a first voltage is applied to said capacitor after said igniter switch is closed, said fire started integrated circuit is operative to conduct a current, said capacitor is operative to discharge said current to ground, and said spark transformer is operative to impose a second voltage across said spark gap. In another embodiment, said electrode tip is mounted substantially flush with said perforated heater plate, protruding from said perforated heater plate, or recessed from said perforated heater plate. In another embodiment, the thermal spray gun further comprises: a normally-closed dead man's switch that is operative to shut off said propane input stream when said dead man's switch is not depressed. In another embodiment, the thermal spray gun of claim 1 further comprises: a shroud that surrounds at least a portion of said heater assembly; and a heat shield that surrounds at least a part of said shroud. In another embodiment, the thermal spray gun further comprises: an umbilical comprising the following components: a propane hose, a single air hose, a powder hose, a plurality of signal wires, a spark ignition power wire, and an electrical ground; wherein said components are bundled within a protective sleeve. In another embodiment, the thermal spray gun further comprises: a valve (e.g., a needle valve) for controlling the rate of flow of said combustion air amplifier air input stream.
In another illustrative embodiment, the invention is a thermal spray gun comprising: means for receiving a propane input stream and a main air input stream, dividing said main air input stream into a combustion air amplifier air input stream and an upper air amplifier air input stream, and combining said propane input stream with said combustion air amplifier air input stream to produce a combustion gas and air stream; means for receiving said combustion gas and air stream, said means for receiving comprising a perforated heater plate and a diverter cone; means for igniting said combustion gas and air stream and producing a flame on said perforated heater plate, said means for igniting comprising an electrode tip; means for taking up said upper air amplifier air input stream and producing a diverter air amplifier high velocity air stream and a cooling air amplifier high velocity air stream, said diverter air amplifier high velocity air stream acting to draw a diverter air inlet stream into said means for taking up said upper air amplifier air input stream to produce an inner diverter outlet steam and an outer diverter outlet stream, and said cooling air amplifier high velocity air stream acting to draw a cooling air inlet stream into said means for taking up said upper air amplifier air input stream to produce a cooling air outlet stream; and means for accepting a powder feed input stream and producing a powder feed outlet stream, said means for accepting comprising a feed tube tip; wherein said inner diverter outlet stream is operative to cool said feed tube tip and said diverter cone and to surround said powder feed outlet stream; and wherein said outer diverter outlet stream is operative to urge said flame radially outward. In another embodiment, said means for receiving is further operative to divide said main air input stream into said combustion air amplifier air input stream, said upper air amplifier air input stream, and a shielding air inlet stream; and wherein said means for accepting is further operative to receive said shielding air inlet stream and to produce a shielding air inlet stream that is operative to cause said powder feed outlet stream to contract to produce a powder contraction zone and then to expand to produce a powder expansion zone.
In another illustrative embodiment, the invention is a method for thermal spraying comprising: receiving a propane input stream and a main air input stream in a thermal spray gun, dividing said main air input stream into a combustion air amplifier air input stream and an upper air amplifier air input stream, and combining said propane input stream with said combustion air amplifier air input stream to produce a combustion gas and air stream; receiving said combustion gas and air stream in a means for receiving, said means for receiving comprising a perforated heater plate and a diverter cone; igniting said combustion gas and air stream and producing a flame on said perforated heater plate; taking up said upper air amplifier air input stream and producing a diverter air amplifier high velocity air stream and a cooling air amplifier high velocity air stream, said diverter air amplifier high velocity air stream educting a diverter air inlet stream to produce an inner diverter outlet steam and an outer diverter outlet stream, and said cooling air amplifier high velocity air stream educting a cooling air inlet stream to produce a cooling air outlet stream; and accepting a powder feed input stream and producing a powder feed outlet stream; wherein said inner diverter outlet stream is operative to surround said powder feed outlet stream; and wherein said outer diverter outlet stream is operative to urge said flame radially outward. In another embodiment, the method further comprises: dividing said main air input stream into said combustion air amplifier air input stream, said upper air amplifier air input stream, and a shielding air inlet stream; and receiving said shielding air inlet stream to produce a shielding air inlet stream that is operative to cause said powder feed outlet stream to contract to produce a powder contraction zone and then to expand to produce a powder expansion zone.
In another illustrative embodiment, the invention is a thermal spray gun comprising: a manifold assembly that is operative to receive a propane input stream and a main air input stream, to divide said main air input stream into a combustion air input stream and a cooling air input stream, to combine said propane input stream with said combustion air input stream to produce a combustion gas and air stream, to divide said cooling air input stream into a diverter air amplifier high velocity air stream and a cooling air amplifier high velocity air stream, said diverter air amplifier high velocity air stream being operative to draw a diverter air inlet stream into said manifold assembly to produce an inner diverter outlet steam and an outer diverter outlet stream, and said cooling air amplifier high velocity air stream acting to draw a cooling air inlet stream into said manifold assembly to produce a cooling air outlet stream; a heater assembly that is operative to receive said combustion gas and air stream, said heater assembly comprising a heater plate; an igniter that is operative to ignite said combustion gas and air stream to produce a flame on said heater plate; and a feed tube assembly that is operative to receive a powder feed input stream and to produce a powder feed outlet stream. In another embodiment, said manifold assembly is further operative to divide said main air input stream into said combustion air amplifier air input stream, said upper air amplifier air input stream, and a shielding air inlet stream; and wherein said feed tube assembly is further operative to receive said shielding air inlet stream and to produce a shielding air inlet stream that is operative to cause said powder feed outlet stream to contract to produce a powder contraction zone and then to expand to produce a powder expansion zone. In another embodiment, said igniter further comprises a conductive electrode tube having an electrode inlet hole and an annular void, an electrode insulator and an electrode, said electrode being separated from said electrode tube by said electrode insulator. In another embodiment, said electrode inlet hole and an annular void receive a portion of said combustion gas and air stream and produce a pilot gas air mixture stream that is ignitable by a spark traveling across a spark gap between said tip electrode and said electrode tube.
In another embodiment, the thermal spray gun further comprises: an electronic ignition circuit comprising: a step-up transformer, a normally-open relay, an igniter switch, a micro-controller that energizes said normally-open relay when said igniter switch is closed, a capacitor, a spark transformer, and a fire starter integrated circuit; wherein, when a first voltage is applied to said capacitor after said igniter switch is closed, said fire started integrated circuit is operative to conduct a current, said capacitor is operative to discharge said current to ground, and said spark transformer is operative to impose a second voltage across said spark gap. In another embodiment, said electrode tip is mounted substantially flush with said perforated heater plate, protruding from said perforated heater plate, or recessed from said perforated heater plate. In another embodiment, the thermal spray gun further comprises: a normally-closed dead man's switch that is operative to shut off said propane input stream when said dead man's switch is not depressed. In another embodiment, the thermal spray gun further comprises: a shroud that surrounds at least a portion of said heater assembly; and a heat shield that surrounds at least a part of said shroud. In another embodiment, the thermal spray gun further comprises: an umbilical comprising the following components: a propane hose, an air hose, a powder hose, a plurality of signal wires, a spark ignition power wire, and an electrical ground.
In another illustrative embodiment, the invention is a thermal spray gun comprising: an umbilical comprising a gaseous fuel hose, a powder hose, and an air hose that is operative to convey a main air input stream; a manifold assembly that is operative to divide said main air input stream into a plurality of air streams, one of which is a combustion gas and air stream and another of which is a hot air stream; a heater assembly that is operative to receive and combust said combustion gas and air stream; a thermal spray gun on-off switch that is operable to turn the thermal spray gun off when released by an operator; a spark ignition electrode assembly that is operative to ignite said combustion gas and air stream within said heater assembly when activated by said operator; a shielded powder tube assembly comprising a powder feed tube that is shielded from said hot air stream by a shielding air tube powder feed tube and that extends into said hot air stream. In another embodiment, said umbilical comprises a gaseous fuel hose, a powder hose, and a single air hose that is operative to convey a main air input stream. In another embodiment, said powder feed tube extends about three inches into said hot air stream.
Further aspects of the invention will become apparent from consideration of the drawings and the ensuing description of exemplary embodiments of the invention. A person skilled in the art will realize that other embodiments of the invention are possible and that the details of the invention can be modified in a number of respects, all without departing from the concept. Thus, the following drawings and description are to be regarded as illustrative in nature and not restrictive.
The features of the invention will be better understood by reference to the accompanying drawings which illustrate exemplary embodiments of the invention. In the drawings:
The following reference numerals are used to indicate the parts and environment of an illustrative embodiment of invention on the drawings:
Referring to
In this embodiment, material is supplied to spray gun applicator 4 by means of a fluidized bed hopper 6. The rate of supply is controlled by two venturis (not shown). The first venturi transports a stream of the powder material particles in compressed gas from fluidized bed hopper 6 to umbilical 3. The second venturi adds additional transport air to the umbilical 3 and ejects the stream of powder material particles into spray gun 4. Each of the first venturi and second venturi is independently controlled by a different individual stream of compressed gas. Fluidized bed hopper 6 is commercially available in several hopper sizes from a number of manufacturers, such as Powder Parts Inc., Elgin, Ill. 60123.
Referring to
In a preferred embodiment, a combination of vibrator 16 and fluidized bed hopper 6 provides superior powder transport capabilities. The combination is effective at de-agglomerating and fluidizing powders for transport between fluidized bed hopper 6 and spray gun applicator 4 through a powder hose within umbilical 3, with the types of thermoplastic powders used to create thermoplastic fusible coatings.
The thermal spray system described herein may be used for depositing a variety of coating materials, including zinc, aluminum, zinc-aluminum alloy, ferrous metal alloys, copper, copper alloys, ceramics, carbon, graphite and combinations thereof. They may also be used for depositing other materials, such as colorants, electrically conductive materials, fluorescent materials, phosphorescent materials, anti-fouling agents, reflective materials, radar absorbent materials, anti-microbials, microballoons, foaming agents, leveling agents, lubricants, ultraviolet (UV) protectors and combinations thereof. Still other materials suitable for deposition using thermal spray system 4 include thermoplastic or thermoset polymeric materials, such as epoxy resins, polyurethanes, polyethers, nylons, polyesters, polycarbonates, polyethylene, polypropylene, acrylic polymers, polyvinylchloride (PVC) resins, fluorocarbon polymers, ethylenevinylacetate (EVA), ethyleneacrylicacid (EAA), acrylonitrilebutadienestyrene (ABS), polyetheretherketone (PEEK), Polyvinylidenfloride (PVDF), silicones and chemical or physical combinations thereof. Coating materials may be combined with other materials. Particle sizes for the coating materials may range from about 5 microns to about 5,000 microns.
Referring to
Referring to
In the embodiment of
A person having ordinary skill in the art would know that a variety of other flame anchoring means are used in flame systems, such as stoves and fueled jets. These flame anchoring means may also be incorporated into embodiments of the invention. Thus, the foregoing examples provide a basic insight into the process of flame anchoring and should not be construed as limitations on the invention.
The heat of combustion at stoichiometric conditions for burning propane in air is 1,980° C. This temperature is too high to be contained by most common refractory materials. For example, high temperature steel alloys have a service temperature of 537° C. Nickel-chromium-iron alloys are used up to 677° C. Even ceramic coated jet engine parts only operate at a maximum temperature of 1,371° C. Therefore, background art flame generating devices are configured so that the flame burns outside the device architecture in free air. For these reasons, in certain embodiments of the invention, in order to contain combustion, film cooling on the flame containment surfaces and heat transfer management are employed.
The desired process temperature for a thermoplastic sprayer device is a hot gas temperature that exits the device in the neighborhood of 700° C., but could range from 100° C. to around 1,000° C. Here, “around” means “approximately” as it is defined above. Most fusible materials are processed in this temperature range. Because combustion temperatures are much higher than preferred fusible material processing temperatures, and to provide a stream of heated carrier gas, in illustrative embodiments of this invention, excess air 12 and cooling gas 13 are introduced to the process during combustion and after combustion is completed.
Referring to
Coanda or attached flow fluid amplifiers are known in the art of fluidics. It is the coupling of a fluid amplifier to a burner or flame tube located within combustion chamber 11 that provides at least two functions. First, excess air 12 serves to complete combustion and begin cooling the flame. Second, the cooling or dilution air 13 serves to further reduce the temperature of the combustion products to achieve the desired flameless hot carrier gas for processing of polymer powders or other materials. Both described functions are accomplished using relatively low quantities of compressed air by means of a Coanda fluid amplifier.
Referring to
Background art venturi style eductors generally do not provide enough primary air to create a stoichiometric mixture and therefore tend to burn rich and require additional oxidant air at the burner. This problem is solved by the applicants by de-coupling the propane gas flow 8, which is typically the motive flow in a pre-mix venturi eductor, from the air venturi and instead using an independent Coanda pre-mix fluid flow amplifier 36, run by primary air 9 and educting additional air 209, in combination with propane fuel gas nozzle 208, e.g., a propane jet orifice, that discharges into the entrance of pre-mix fluid amplifier 36.
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
In a preferred embodiment, thermal spray system 1 comprises single air supply applicator 301. Referring to
In this embodiment, heat shield 310 is a secondary cone that surrounds shroud 309. Shroud 309 may reach temperatures in excess of 500° C., but the addition of heat shield 310 reduces the temperature of the exterior of heat shield 310 to less than 250° C. In this embodiment, shroud 309 is passively cooled by air educted between shroud 309 and heat shield 310 and heat shield 310 blocks heat radiating from shroud 309.
In a preferred embodiment, dead man's switch 370 and robust feed switch 318 are provided in the handle of single air supply applicator 301. Referring to
In this embodiment, three air streams and a propane stream come together in single air supply applicator 301 to create an ideal nameless spray environment. These flow streams are illustrated in
In this embodiment, propane input stream 313 flows through propane input tube 315 and is normally shut off with propane valve 316. Propane valve 316 may be opened by depressing propane valve lever 317 and allowing the propane to flow into lower air manifold assembly 308. The propane valve 316 and propane valve lever 317 comprise dead man's switch 370.
Main air input stream 312 flows through main air tube 314 and into lower air manifold assembly 308. In lower air manifold assembly 308, main air stream 312 is split to travel into heater assembly 302 and into upper air manifold assembly 304. The portion of main air supply input stream 312 that is directed into heater assembly 302 by lower air manifold assembly 308 is mixed with propane from propane input stream 313 to create combustion gas and air stream 319. Combustion gas and air steam 319 is preferably a stoichiometric mixture of propane gas and air, which can burn cleanly and completely.
In this embodiment, three other air streams are input to the back end of single air supply applicator 301. The first air stream, powder feed input stream 320, is a mixture of pressurized air and powder supplied to single air supply applicator 301 by a powder feed pump (not shown). Powder feed input stream 320 carries the fusible powder that is melted in single air source applicator 301. The second air stream is diverter air inlet stream 321, which is drawn into the back of single air supply applicator 301 by upper air manifold assembly 304. The third air stream is cooling air inlet stream 322, which is also drawn into the back of single air supply applicator 301 by upper air manifold assembly 304.
As the air flows from right to left in the embodiment shown in
In this embodiment, inner diverter outlet steam 324a and outer diverter outlet stream 324b divide diverter air inlet stream 321 as the air flows over diverter cone 326. Inner diverter outlet stream 324a keeps the tip of feed tube assembly 305 and diverter cone 326 cool so that powder 229 will not stick to these surfaces. Also, inner diverter outlet stream 324a surrounds powder feed outlet stream 323 to prevent flames from heater assembly 302 from directly contacting powder 229 in the powder feed outlet stream 323. Outer diverter outlet stream 324b forces the flame on the outlet side of heater assembly 302 radially outward toward shroud 309. Forcing the flame radially outward prevents the flame from directly contacting powder 229 in powder feed outlet stream 323 and keeps the flame anchored within shroud 309. Referring to
Referring to
Referring to
Referring to
During operation, a high voltage electrical potential is repeatedly applied to electrode lead wire 334 and passes through electrode 332. The high voltage potential is sufficient to create a spark, which travels from the electrode tip 328 across the pilot gas air mixture stream 335 to electrode tube 330. By forcing the spark through pilot gas air mixture stream 335, the flame can reliably be ignited in heater assembly 302.
Referring to
In this embodiment, only igniter switch S1, electrode 303, microcontroller U1, fire starter integrated circuit FLC-200B U2, capacitor C1, and spark transformer T2 are attached to single gas supply applicator 301. The other components are preferably installed on a separate cart 2. The circuit connections between the components attached to the single gas supply applicator 301 are connected to the components installed on cart 2 by an electrical umbilical cable 3.
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
In a preferred embodiment, powder feed tube 357 is made from 5/16 inch outside diameter stainless steel tubing with a 0.028 inch wall thickness. Shielding air tube 358 is preferably made from ½ inch outside diameter stainless steel tubing with a 0.028 inch wall thickness. In this embodiment, the volumetric flow rate of shielding air input stream 362 ranges from 1.0-5.0 standard cubic feet per minute (SCFM), and is approximately 1.5 SCFM for a 30 kW power setting.
Referring to
Powder contraction zone 364 and powder expansion zone 365 may be altered by adjusting the shielding air volume flow rate. In addition, alternate feed tube and shielding tube diameters and shapes are envisioned, which can create a variety of spray patterns.
In preferred embodiments, the invention possesses a number of advantageous features. These embodiments comprise air manifold assemblies 308 and 337 which divide air provided to single air source applicator 301 in air hose 375 into a plurality of air flow streams. The single air supply embodiment is lighter and less cumbersome than embodiments that require multiple air supplies. A propane dead-man's switch 370 is provided on handgrips 306a and 306b as a safety feature. If applicator 301 is dropped, propane flow stops and combustion stops. A spark ignition electrode assembly 303 is provided to light the combustor for the convenience of the operator. When the operator picks up the unit, he squeezes dead-man's switch 370, presses igniter button 384, and applicator 301 begins generating large quantities of heat. Providing shielded powder tube assembly 355 results in an improved powder deposition pattern and eliminates fouling. The presence of shielding air tube 358 allows powder feed tube 357 to be extended (e.g., approximately three inches) into a hot air stream that includes inner diverter outlet stream 324a and outer diverter outlet stream 324b. Igniter 303 provides a more reliable means for igniting the propane/air mixture.
Many variations of the invention will occur to those skilled in the art. All such variations are intended to be within the scope and spirit of the invention. Some variations include trip plates, trip lips and/or bluff bodies. Other variations call for flame tubes, holes or perforated walls, serpentine paths and/or fluid amplifiers with annular nozzles and/or air knives. All such variations are intended to be within the scope and spirit of the invention.
Although some embodiments are shown to include certain features or steps, the applicants specifically contemplate that any feature or step disclosed herein may be used together or in combination with any other feature or step on any embodiment of the invention. It is also contemplated that any feature or step may be specifically excluded from any embodiment of the invention.
This application claims the benefit of U.S. Provisional Patent Application No. 61/459,631, filed Dec. 15, 2010, the disclosure of which patent application is incorporated by reference as if fully set forth herein. This application is also a continuation in part of U.S. patent application Ser. No. 12/657,211, filed Jan. 14, 2010, which claims the benefit of U.S. Provisional Patent Application No. 61/205,079, filed Jan. 14, 2009, the disclosures of which patent applications are incorporated by reference as if fully set forth herein.
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Grant No. FA8651-04-C-0379 awarded by the United States Air Force.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3159348 | Wedan | Dec 1964 | A |
| 3801020 | Mocarski | Apr 1974 | A |
| 3958758 | Piorkowski | May 1976 | A |
| 4416421 | Browning | Nov 1983 | A |
| 4632309 | Reimer | Dec 1986 | A |
| 4694990 | Karlsson et al. | Sep 1987 | A |
| 5148986 | Rusch | Sep 1992 | A |
| 5236327 | Flanagan et al. | Aug 1993 | A |
| 5285967 | Weidman | Feb 1994 | A |
| 5503872 | MacKenzie et al. | Apr 1996 | A |
| 5932293 | Belashchenko et al. | Aug 1999 | A |
| 6245390 | Baranovski et al. | Jun 2001 | B1 |
| 7216814 | Gardega | May 2007 | B2 |
| 20060166153 | Rusch et al. | Jul 2006 | A1 |
| 20090095823 | Gardega et al. | Apr 2009 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 61459631 | Dec 2010 | US | |
| 61205079 | Jan 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12657211 | Jan 2010 | US |
| Child | 13374201 | US |
