Patent Application
20070114304
The present invention relates to particulate spray guns. More specifically, the invention pertains to a nozzle extension for a supersonic particulate spray machine for conveying the high speed particles to a workpiece surface which is not disposed in the line of sight of the spray machine's normal output.
Supersonic gas dynamic spray (GDS) technology has proven highly efficient for applying dense coatings to various flat workpiece surfaces. There is a great demand in industry for cost effective application of such dense coatings on inside cylindrical surfaces of elements such as engine blocks, tubes, pipes and artillery gun barrels to enhance the wear resistance of components resident inside such cylindrical openings and to provide corrosion resistance to protect such surfaces from attack by materials flowing through the cylindrical passages of such elements. Applying the GDS technology to such cylindrical interior surfaces has presented problems in the past, because GDS is basically a line-of-sight process. Known angled extensions for GDS nozzles suffer from clogging problems which tend to manifest themselves in extremely short time periods, thereby substantially increasing the cost of arising from frequent required replacement.
Therefore there is seen to be a need in the art for a nozzle extension having an output angled away from the longitudinal center line of the output of the spray machine nozzle and capable of resisting clogging and maintaining the velocity of the accelerated particulates above a critical speed allowing for formation of dense coatings.
A nozzle extension for use with a nozzle of a particulate spray machine includes a substantially linear hollow input section having an input end and an output end, the input end adapted to be coupled to the nozzle, the input section having a longitudinal axis and an input section inner diameter. A hollow curvilinearly angled output section of the extension has an input end coupled to the output end of the input section and an output end adapted for discharging particulate spray toward a workpiece surface. A longitudinal axis of the input end of the output section is substantially aligned with the longitudinal axis of the input section. The longitudinal axis of the output end of the output section extends at a non-zero angle to the longitudinal axis of the input section, and the output section has an output section interior diameter greater than the input section interior diameter.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
Gas dynamic spraying uses a supersonic converging/diverging (de Laval-type) nozzle. A heated, high pressure carrier gas is supplied upstream of the converging portion of the nozzle and the powdered particulate material is introduced into the carrier gas stream in the nozzle. Coatings are produced by entraining metal powders in an accelerated air stream through a supersonic nozzle and projecting them against a target substrate, normally as close to a 90° angle as possible. It is believed that for the particulate matter to adhere to a substrate, they must break the oxide shell on the substrate material permitting subsequent metallurgical bond formation between plastically deformed particles and the substrate. It is imperative for the accelerated particles to exceed a critical velocity prior to their being able to bond successfully with the substrate.
One suitable form of gas dynamic spray system 300 is set forth in block diagram form in
Multiple powder hoppers 304a, b provide different desired powder compositions for different applications to powder inlet 318 of nozzle 302. Heater element 314 heats the gas to a temperature less than the melting point of the powder. Powder compositions from powder hoppers 304a and 304b are directed into nozzle 302 due to negative pressure created at the point of injection 318. The nozzle 302 propels the powder particles which are deposited atop a substrate as a bulk build-up of material.
With reference to
An output end 120 of input section 102 is in fluid communication with the interior of a curvilinear output section 106 of extension 100. The extension of
Output section 106 has an input end with a longitudinal axis substantially aligned with axis 108 of the input section 102. Output section 106 has a longitudinal axis 110 at its output 124 which extends at a non-zero angle to axis 108. This angle A, or 114, is shown in
The internal diameter of the hollowed portion of curvilinear section 106 is larger than that of input section 102. The resultant shape of the interior of section 106 induces peripheral turbulence in the particulate flow entering section 106 from output end 120 of section 102, thereby inhibiting adhesion of the particles to the interior surface of curvilinear section 106 as well as erosion of curvilinear section 106. Hence, clogging and erosion are minimized, or at least substantially delayed, with this design.
Angle A of
As stated previously, the internal diameter of the hollow portion of section 106 is larger than the internal diameter of section 102. A preferred range of ratios of the internal diameter of section 106 to that of section 102 is between about 1.5 and about 3.5, more preferably between about 1.5 and about 3.0.
One specific extension as shown in
With reference to
Nozzle extension 100 can be fashioned from either metal or ceramics and, as mentioned above, may be comprised of a plurality of sections having means for joining the sections together or can be made as a single unitary piece. Each extension section can have a cylindrical, elliptical or polygonal internal opening carrying an inner liner of an abrasion resistant material for protecting the inner surface against abrasion by the particulate flow therethrough. The abrasion resistant inner liner should have an outer surface with a shape that corresponds and conforms to the inner surface of the extension section.
With the nozzle extension arranged as shown, it can be rotated about the axis of the supersonic nozzle outlet allowing formation of an even coating on surfaces being sprayed. Such an extension placed at the output of the spray gun nozzle enables spraying of internal surfaces of tubular-shaped parts with small diameter.
Due to the internal geometry of extension 100, the velocity of the accelerated particles above a critical speed is maintained, thereby allowing for a dense coating to be formed on a workpiece surface.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
