I. Field of the Invention
The present invention relates to the concepts of cold spraying. More specifically, but not exclusively, the present invention relates to a device and system for cold spraying by upstream mixing and hand-held or robotic manipulated nozzle operation.
II. Description of the Prior Art
The existing systems for cold spraying metal particles operate by mixing a pressurized gas together with a stream of powdered metallic particles. The resulting gas/metallic particle mixtures are sprayed onto an object, thereby applying the metallic particles to the surface of the object.
In a cold spray process, specially engineered sub-micron and micron sized solid state particles are accelerated to supersonic speeds through a convergent-divergent nozzle using such gases as helium and nitrogen or other like gases or even compressed air. When the particles impact the surface, they form a strong mechanical and metallurgical bond.
Currently, all existing cold spray systems mix the metallic powder and gas streams very near, at, or directly after the throat of a spray nozzle (i.e., within the spray nozzle body). For this reason, a heater is often included in the nozzle/spray gun assembly. This poses multiple problems, such as, the cold spray nozzle assembly must be large, and must be made even larger when gas pressures increase above 250 psi because the size of the heater must also grow to heat a greater quantity of gas; and the maneuver ability of the cold spray nozzle is limited because the powder supply feed line (which may be densely packed with flowing powder) cannot be easily manipulated because twists and kinks can cause blockages in the line. In such systems, the powder may be discharged from the nozzle at a temperature significantly lower than the temperature of the accelerant (i.e., the gas).
Therefore, a primary object, feature, or advantage of the present invention is to provide a cold spray device and system that includes a compact and highly maneuverable spray nozzle.
Another object, feature, or advantage of the present invention is to precisely control the temperature of the powder at discharge from the nozzle.
As still further object, feature, or advantage of the present invention is to provide a cold spray device and system that mixes the powder and accelerant upstream of the spray nozzle.
One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow.
One embodiment provides a device and system for cold spraying. The cold spray system includes a spray nozzle having an input side and a discharge side. A gas flowpath, a powder flowpath, and a confluence of the gas flowpath and the powder flowpath provide a gas-powder mixture. A gas-powder mixture flowpath between the confluence and the nozzle carry the gas-powder mixture to the input side of the spray nozzle.
Another embodiment provides a cold spray device. A gas-powder mixture is discharged from a nozzle body. A gas-powder mixture input side on the nozzle body is adapted for downstream communication with a gas-powder mixing manifold. The nozzle body may include a gas-powder mixture output side. A gas-powder flowpath may be in communication with the input side and output side. The gas-powder mixture includes a gas temperature and a powder temperature, wherein the powder temperature is generally at the gas temperature at the input side. In a preferred aspect, the cold spray device includes a gas-powder line housing the gas-powder flowpath, wherein the gas-powder line is connected between the inlet on the input side and a spray nozzle on the output side.
Yet another embodiment provides a cold spray system. The cold spray system includes a flowpath having an inlet adapted for receiving communication with two or more inputs and an outlet adapted to discharge at least the two or more inputs. A discharge nozzle may be included in the flowpath at the outlet. A confluence in the flowpath may be included at the inlet for combining the two or more inputs. A nozzle body may be configured to house the discharge nozzle separate and downstream from the confluence. In a preferred aspect, a single line houses the flowpath between the confluence and the nozzle body.
Illustrative embodiments of the present invention are described in detail below with reference to the attached drawings figures, which are incorporated by reference herein and wherein:
The illustrative embodiments provide a cold spray device and system. Embodiments benefit from, at least, (a) the mixing of the accelerant (i.e., gas) and the metallic powder upstream of the spray nozzle assembly; and therefore, (b) there is no requirement that a heater or heating element be included in the spray gun assembly.
Embodiments of the present invention place the heater near or proximate the powder feeder and mix the powder and heated gas lines very near to the system components, and then transport the powder together with the heated air as a much less dense mixture which is supplied to a spray nozzle. As a result, the embodiments of the invention are highly maneuverable, compact and much less likely or sensitive to clogging due to twisting, bending, or crimping of a powder supply line.
Moreover, the absence of the heater or heating element in the spray nozzle assembly results in a much smaller and more compact spray nozzle. As such, the spray nozzle can be easily manipulated, and may advantageously be mounted on an automated, robotic or machine-manipulated system (or otherwise some automation means) having appreciably more freedom of motion. One embodiment may include using a six-axis robotic arm for manipulating the spray nozzle thereby leveraging the aforementioned advantages of the various embodiments. In addition, since embodiments of the invention do not require long powder lines attached and extending from the spray nozzle, thereby decreasing the danger of kinks or twists resulting in the line and then causing a blockage of conveyance of the powder. Thus, the absence of a powder line connected to the spray nozzle results in a much more compact and highly maneuverable spray nozzle assembly.
Embodiments of the invention also increase the resident time of the powder particles in the heated gas stream, allowing time for heat in the gas stream to transfer from the heated gas supply to the powder particles suspended in the gas stream. This preheating of the particles softens the particles prior to impact, making the particles more deformable and capable of achieving higher bonding strengths. In conventional powder spray systems, the powder is introduced into the spray nozzle only a very short distance from the substrate, to the effect that there is virtually no time for the heat in the accelerant (i.e., in the gas) to transfer to suspended particulate matter (i.e., powder).
Embodiments of the invention are ideally suited for repairing damage or worn metal subjects in need of repair, particularly, where such repairs require working in tight spaces. Embodiments of the invention can be reduced significantly in size from conventional cold spray devices and systems and therefore have a high degree of maneuverability. Thus, the embodiments of the invention provide greater access and maneuverability of the spray nozzle assembly as compared to conventional cold spray devices and systems.
Embodiments of the invention also allow for use of high pressure gas supplies, which have been consistently shown to be capable of the highest quality repairs (the use of lower pressures generally leads to lower or even unacceptable quality of repairs). Altogether, the embodiments of the invention make possible the use of a hand-held and field deployable cold spray device and system for making the highest quality repairs, which greatly exceed the current capability of conventional cold spray devices and systems.
The pressure and flow rate of the gas in flowpath 412 may be regulated to different pressures and flowrates than the gas in flowpath 422. Gas in flowpath 422 travels in the direction of flow arrow 420 through a heat source 424 that imparts heat to the gas which then flows through flowpath 428 into mixing manifold 430 in the direction as indicated by the flow arrows 426. Thus, one of the inputs into the mixing manifold 430 is a heated gas stream having a desired flow rate, pressure and temperature operably provided by the heat source 424 and the gas controller 402. Additionally, gas flows through flowpath 412 as indicated by flow arrows 410 into the powder source 414. The gas flowing into the powder source 414 carries with it powder through flowpath 418 as indicated by flow arrow 416 into the mixing manifold 430. Thus, a mixture of powder and gas provide another input into the mixing manifold 430, which provides a mixing function of the two inputs provided through flowpath 428 and flowpath 418. The two inputs, for example, include a heated affluent or accelerant, such as a heated gas stream, and a powder carried by the other gas stream into the mixing manifold 430. The pressure and volume of the flows in the flowpaths 428, 418 may be controlled to control the inputs into the mixing manifold 430 and mixing of the inputs. The temperature and pressure of the inputs into the mixing manifold 430 may be used to control the temperature of the discharge (i.e., cold spray) from the spray nozzle assembly 436. In other words, the stagnation pressure of a supersonic nozzle, such as the spray nozzle assembly 436, may be controlled by controlling the pressure and temperature of its inputs, namely the temperature and pressure of an accelerant and powder. The inputs into the mixing manifold 430 are combined and communicated through flowpath 432 as indicated by flow arrow 434 to the inlet 440 of the spray nozzle assembly 436. Means for controlling the flow of the mixture through the spray nozzle assembly 436, such as a valve or other open or closeable type opening may be provided in the spray nozzle assembly 436. The mixture travels through the spray nozzle assembly 436, out the nozzle body 438 and discharged through the outlet 442 onto a surface of interest.
Of specific note, as illustrated pictorially in
Embodiments of the invention pictorially represented in
The gas source 404 may include, for example, nitrogen, helium or compressed air. As previously indicated, gas controller 402 may be used to control the pressure of the gas in flowpaths 422 and 412, respectively. In accordance with an embodiment of the invention, the gas controller 402 may be configured to operate the powder source 414 at or around 500 psi, or at least above 300 psi. Similarly, the gas controller 402 may be configured to pass gas through the heat source 424 at or close to 500 psi, and at least above 300 psi. The heat source 424 may be configured to operate in a temperature range generally from 600-900° C., or thereabout. Preferably, the heat source 424 is configured to operate at a temperature below the melting temperature of the powder. Therefore, the temperature of the gas-powder mixture being discharged from outlet 442 may be controlled by controlling the temperature of the heat source 424 and the pressure of the gas passing through heat source 424 and powder source 414. The temperature of the gas-powder mixture being discharged out the outlet 442 of the spray nozzle assembly 436 may be increased (using gas controller 402) by increasing the temperature of the heat source 424 and/or increasing the pressure of the gas. For example, for lower powder melting temperatures, the temperature of the heat source 424 can be turned down while the pressure of the gas can be increased using the gas controller 402 to compensate for a non-increase in the temperature of the gas or a lower heat source 424 operating temperature. Optionally, an additional heat source may be included in flowpath 412 for heating or preheating the gas passing through powder source 414, whereby both gas streams in flowpaths 418 and 428 are heated streams, with the gas stream in flowpath 418 carrying suspended powder or particulate matter. In a preferred aspect of the invention, the temperature of the gas-powder mixture is to range between 600-900° C. Using a non-heated gas stream for feeding powder from powder source 414 into flowpath 418 may result in a temperature loss in the heated gas stream entering the mixing manifold 430 through flowpath 428 in an order generally between 150-200° C. This temperature loss can be overcome by, for example, heating or preheating the gas passing through flowpath 412 into the powder source 414. Optionally, the powder or particulate matter suspended in the gas may be heated in flowpath 418. Cold spraying high temperature materials (e.g., nickel, titanium, aluminum) may necessitate the discharge temperature of the gas-powder mixture from the outlet 442 of the spray nozzle assembly 436 to be higher than a resulting discharge temperature minus the temperature loss from an unheated gas stream being used to provide powder from the powder source 414. Thus, depending upon the type of material that is being cold sprayed, the system 400 may include a heater or heat source for upstream heating of the gas used to move the powder from the powder source 414 into the mixing manifold 430. Alternatively or in combination, the pressure of the gas in either flowpath 422 or 412 may be increased to increase the temperature of the gas-powder discharge from the outlet 442 of the spray nozzle assembly 436 using means to control the stagnation pressure and temperature of the supersonic nozzle included in the spray nozzle assembly 436. Although a single gas source 404 is illustrated, embodiments of the invention contemplate using multiple gas sources for feeding flowpaths 422 and 412 with the same type of gas or different types of gas.
According to a preferred aspect of the invention, powder or particulate matter communicated from powder source 414 to the mixing manifold 430 combines with heated gas from the heat source 424. The two form a gas-powder mixture which travels together through the flowpath 432 to the spray nozzle assembly 436. In one embodiment (where the gas introduced into the powder source 414 is not heated) the temperature of the powder passing through flowpath 418 and into mixing manifold 430 is less than the temperature of the gas (entering the mixing manifold 430) from heat source 424 through flowpath 428. Thus, heat is transferred from the heated gas to the powder as it travels through flowpath 432 to the spray nozzle assembly 436.
The illustrative embodiments and the different and distinct components, features, and elements of each of the embodiments may be combined in any number of combinations and such combinations are expected and utilized. The number of combinations and alternative embodiments is not limited nor intended to be limited based on the included disclosure.
The previous detailed description is of a small number of embodiments for implementing the invention and is not intended to be limiting the scope. The following claims set forth a number of embodiments of the invention disclosed with greater particularity.
This application claims priority under 35 U.S.C. § 119 to provisional application Ser. No. 61/719,632 filed Oct. 29, 2012, herein incorporated by reference in its entirety.
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