Claims
- 1. In a powder delivery system for spraying powder entrained in an air stream wherein the system includes a powder spray controlling gun, means for conveying an air stream entraining powder from a pump to said gun, a gun barrel integral with said gun and an elongated lance extension having a rear end operatively mounted on said forward end of said gun barrel for conveying powder from said forward end of said barrel of said powder spray gun at a rearward, upstream end of the extension to a spray nozzle spaced from said gun and disposed at a forward, downstream end of the lance extension, said extension comprising an elongated tube having a length of about 6 to about 24 inches and having an inner surface comprising an elongated internal bore of substantially constant diameter defining a path for powder blown by an air stream therethrough in a downstream direction from said gun to said nozzle, and an electrode sleeve extending through said extension and defining with said extension a powder stream flow path having a cross-sectional flow area; the improvement comprising:
- venturi means for homogenizing powder within said air stream in said lance extension, said venturi means including;
- an elongated venturi sleeve having upstream and downstream ends and being disposed within the upstream, rearward one-third of said lance extension tube and between forward and rearward ends of said extension;
- an internal bore in said venturi sleeve defining a portion of said path and terminating at a downstream end of said sleeve within said tube;
- a tapered bore in said venturi sleeve coaxial with and operatively communicating with the internal bore in said sleeve, said tapered bore extending from one diameter near said internal venturi sleeve bore to a greater diameter in an upstream direction from said internal sleeve bore;
- said downstream end of said venturi sleeve comprising a flat face in a radial plane, said internal bore of said venturi sleeve terminating at a port in said face radially spaced inward from said inner surface of said extension tube and opening abruptly into said tube;
- said electrode sleeve extending through said internal bore and said tapered bore in said venturi sleeve and defining therewith a powder stream flow path having a cross-sectional flow area through said venturi;
- said venturi means creating increased velocity and turbulence within said path in said lance extension tube when air and powder are blown therethrough, thereby homogenizing powder within said air stream and within said lance extension tube beyond said gun barrel forward end, but upstream of said spray nozzle, and whereby said turbulence is diminished in the downstream two-thirds of said extension tube to provide a homogenized uniform powder and air stream to said nozzle for discharge therefrom in a uniform pattern.
- 2. A lance extension as in claim 1, wherein said electrode sleeve within said lance extension, extends through said elongated internal bore of said extension tube and through said internal bore of said venturi sleeve, and wherein the cross-sectional flow area of the powder stream flow path defined between said electrode sleeve and the inner surface of said lance extension tube is at least four times greater than the cross-sectional flow area of the powder stream flow path defined between said internal bore of said venturi sleeve and said electrode sleeve.
- 3. Apparatus as in claim 1, wherein said venturi sleeve is about 1.5 inches long, the downstream internal bore of said venturi sleeve is about 1/4 inch to about 3/8 inches long, the inside diameter of said lance extension tube bore is about 0.812 inch, and said venturi sleeve is disposed in said lance extension a distance from the rear, upstream end thereof in the approximate range of 2 inches to 8 inches.
- 4. A lance extension as in claim 1, wherein said lance extension includes an electrode means for charging powder particles, said electrode passing axially through said electrode sleeve in said lance extension and through said internal bore of said venturi sleeve, wherein said powder stream flow path defined between said internal bore of said venturi sleeve and said electrode sleeve is in the shape of a first annulus having a first cross-sectional flow area, and wherein said powder stream flow path defined between said inner surface of said extension tube and said electrode sleeve is in the shape of a second annulus, downstream of said first annulus, having a second cross-sectional flow area at least four times greater than that of said first annulus.
Parent Case Info
This is a continuation of application Ser. No. 638,391, filed Aug. 3, 1984, now abandoned.
US Referenced Citations (12)
Foreign Referenced Citations (2)
Number |
Date |
Country |
2519273 |
Jul 1973 |
FRX |
2229206 |
Dec 1974 |
FRX |
Continuations (1)
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Number |
Date |
Country |
Parent |
638391 |
Aug 1984 |
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