Combustion – Porous – capillary – particulate or sievelike flame holder,... – Means supplying fuel for passage through the flame holding...
Reexamination Certificate
2001-04-26
2004-05-18
Price, Carl D. (Department: 3749)
Combustion
Porous, capillary, particulate or sievelike flame holder,...
Means supplying fuel for passage through the flame holding...
C431S326000, C431S007000, C239S418000, C239S548000, C239S552000, C239S568000, C239S543000, C239S553500
Reexamination Certificate
active
06736633
ABSTRACT:
BACKGROUND OF THEN INVENTION
This invention relates to novel burner manifold apparatuses. More particularly, this invention relates to burner manifold apparatuses for micromachined burners, such as micromachined silicon burners.
It is known to form various articles, such as crucibles, tubing, lenses, and optical waveguides, by reacting a precursor in the flame of a burner to produce a soot and then depositing the soot on a receptor surface. This process is particularly useful for the formation of optical waveguide preforms made from doped and undoped silica soot, including planar waveguides and waveguide fibers.
The waveguide formation process generally involves reacting a silicon-containing precursor in a burner flame generated by a combustible gas, such as a mixture of methane and oxygen, and depositing the silica soot on an appropriately shaped receptor surface. In this process, silicon-containing materials typically are vaporized at a location remote from the burner. The vaporized raw materials are transported to the burner by a carrier gas. There, they are volatilized and hydrolyzed to produce soot particles. The soot particles then collect on the receptor surface. The receptor surface may be a flat substrate in the case of planar waveguide fabrication, a rotating starting rod (bait tube) in the case of vapor axial deposition (VAD) for waveguide fiber fabrication, or a rotating mandrel in the case of outside vapor deposition (OVD) for waveguide fiber fabrication.
Numerous burner designs have been developed for use in vapor delivery precursor processes, and at least one liquid delivery precursor process has been contemplated, as disclosed in co-pending application Ser. No. 08/767,653 to Hawtof et al, incorporated herein by reference. Whether the precursor is delivered to the burner in vapor form or liquid form, it is important that the burner receives a distributed, even stream of precursor. This consideration is particularly important during waveguide manufacture to form accurate refractive index profiles.
In the recent past, burners for deposition of metal oxide soot have been proposed having orifices and supply channels on a small scale. The channels and orifices in these burners may have widths or diameters less than 150 microns, for example, as disclosed in commonly-owned provisional application Ser. No. 60/068,255 entitled “Burner and Method For Producing Metal Oxide Soot,” incorporated herein by reference.
As a result, there has arisen a need for a burner manifold that may be used in conjunction with these micromachined burners and may distribute fluid uniformly and evenly to the burners. In conventional large-scale burners, this uniformity was achieved by equally large concentric rings. This solution, however, is not practical for use with micromachined burners.
SUMMARY OF THE INVENTION
With the advent of micromachined burners, it is desirable to have a burner manifold apparatus that evenly and uniformly distributes fluid (either vapor or liquid) to the micromachined burners.
A burner manifold apparatus in accordance with the present invention comprises fluid inlets, fluid outlets, and a plurality of fluid passages. The fluid passages extend between the fluid inlets and the fluid outlets to deliver reactants to the combustion site of a chemical vapor deposition process. The fluid passages converge toward each other from the fluid inlets to the fluid outlets in that inlets of the fluid passages are spaced farther apart than outlets of the fluid passages. This arrangement facilitates delivery of reactant precursor fluid from a macro scale delivery system to a micro scale burner. The fluid passages preferably have a smaller cross-sectional area at their outlet than at their inlet.
The fluid passages generally are isolated from one another so that some fluid passages transport reactant precursor materials and other fluid passages transport combustion materials. The fluid passages at the fluid outlets are preferably shaped to match the geometry of the burner. In a preferred embodiment, the fluid outlets are slot shaped or formed as a series of in-line round holes.
The burner manifold apparatus further includes at least one pressure inducing restriction device for passing fluid therethrough in evenly distributed, narrow elongated streams. The pressure inducing restriction device is positioned between the fluid inlets and the fluid outlets. The pressure inducing restriction device preferably comprises a plate having a series of slots or linearly arrayed apertures for emitting fluid therefrom in generally linear streams of droplets.
One embodiment of the present invention includes a manifold base having a top, a bottom, a front wall, a back wall, and two side walls. The manifold base defines horizontal passages therethrough that extend between the side walls, vertical passages extending from a position within the manifold base to the top of the manifold base, and fluid inlet ports. Each fluid inlet port is located on either the front wall or the back wall of the manifold base, and each is in fluid communication with at least one of the horizontal and vertical passages. The horizontal passages preferably are parallel to the top and the bottom of the manifold base, and the vertical passages preferably are parallel-to the side walls of the manifold base.
The burner manifold apparatus of the first embodiment also includes a plate mounted to the top of the manifold base. The plate defines a plurality of apertures therethrough. At least one aperture is positioned at a location above an exit of each of the vertical passages of the manifold base to allow passage of fluid from the vertical passages through the plate.
The vertical passages of the manifold base are symmetric about a first axis bisecting the top of the manifold base. The vertical passages preferably include a central vertical passage and pairs of vertical passages, each pair defined by two vertical passages spaced equidistant from the first axis. Each pair intersects a particular horizontal passage to create an array of passages within the manifold to distribute fluid symmetrically about the first axis.
The apparatus of the first embodiment further includes a manifold burner mount mounted to the top of the plate. The manifold burner mount defines fluid passages that extend from a bottom of the manifold burner mount to a top of the manifold burner mount. These fluid passages are arranged to converge such that a distance between adjacent fluid passages is greater at the inlet of the manifold burner mount than at the outlet of the manifold burner mount.
The burner manifold apparatus further comprises a first gasket positioned between the manifold base and the plate. The first gasket has slots therein in alignment with grooves in the top of the manifold base. A second gasket preferably is positioned between the plate and the manifold burner mount. This second gasket has slots in alignment with the slots in the first gasket. A burner gasket may be placed upon the manifold burner mount. The burner gasket has slots in alignment with the exits of the fluid passages in the manifold burner mount.
Securing elements, such as clamps, may be mounted to the top of the manifold burner mount for releasably securing a burner to the manifold burner mount. The clamps each have an outer edge and an inner edge, and the inner edge has a shoulder that engages the burner. Further, the inner edge of each clamp has a tapered surface that tapers away from the top of the manifold burner mount.
A second embodiment of the subject burner manifold apparatus includes a plurality of manifold elements positioned in a stacked arrangement on top of a base element. The manifold elements fluidly communicate with each other via fluid passages therein. Each of the manifold elements has a different number of fluid passages, preferably increasing by two for each successive element located higher on the stack. These fluid passages converge toward each other at the outlet of the manifold apparatus. Each of the manifold elements has at least one fluid inlet port,
Dawson-Elli David F.
Fu Xiaodong
Hawtof Daniel W.
Kiefer William J.
Stone, III John
Carlson Robert L.
Corning Incorporated
Price Carl D.
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