Fluid sprinkling – spraying – and diffusing – Unitary plural outlet means
Reexamination Certificate
1999-12-03
2001-11-06
Kashnikow, Andres (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Unitary plural outlet means
C239S553000, C239S558000, C239S559000, C239S567000
Reexamination Certificate
active
06311902
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a nozzle and sealing apparatus for chemical delivery systems using a gas delivery tube and, more particularly, to the process of introducing materials into the interior of tubular members through the nozzle.
BACKGROUND OF THE INVENTION
The following discussion deals with starter tubes and the gas delivery system for optical fiber pre-forms, but it is to be understood that principles of the present invention are applicable to other, different applications involving, generally, chemical delivery systems wherein the chemicals are in gaseous or vapor form.
Optical fiber of the type used to carry optical signals is fabricated typically by heating and drawing a portion of an optical pre-form comprising a refractive core surrounded by a protective glass cladding. Presently, there are several known processes for fabricating pre-forms. The modified chemical vapor deposition (MCVD) process, which is described in U.S. Pat. No. 4,217,027 issued in the names of J. B. MacChesney et al. on Aug. 12, 1980 and assigned to Bell Telephone Laboratories, Inc. has been found to be one of the most useful because the process enables large scale production of pre-forms which yield very low loss optical fiber.
During the fabrication of pre-forms by the MCVD process, reactant-containing gases, such as SiCL
4
are passed into a rotating substrate or starter tube which is made of silica glass. A torch heats the tube from the outside as the precursor gases are introduced therein, causing deposition of submicron-sized glass particles or soot on the inside surface of the tube. The torch is moved along the longitudinal axis of the tube in a plurality of passes to build up layer upon layer of soot to provide a pre-form tube. Once a sufficient number of layers have been deposited, the pre-form tube is then heated to cause it to be collapsed to yield a pre-form or pre-form rod as it is often called. The delivery system of the reactant gases to the starter tube interior is generally through a rotating or fixed metallic hollow tube connected to the source or sources of the gases.
In the current method of manufacture, the apparatus which ensures sealed delivery of the deposition chemicals in the gases is a combination of a rotary union element, a structure for holding and sealing the starter tube, and a secondary face seal assembly for routing of purge gases through the structure. This is a complex apparatus that requires frequent maintenance. Existing systems also have the disadvantage of having inherently larger cavities for the accumulation of dead zones of flow, and a tendency to create particle contamination from the rotary union and face seal system. Inasmuch as the chemical delivery system supply is stationary, the current means of achieving delivery is via the rotary union, featuring a transition of the chemicals from a stationary pipe to a rotary pipe or to the inside of a supply coupling. The chemicals being delivered are at a pressure greater than atmospheric, and the face seal properties are the only restriction to the release of the chemicals to the atmosphere. The rotary union and secondary face seals generate a large quantity of particles from wear, and contribute to the contamination of the coupling. The complexity of the components involved requires skilled maintenance being performed using requalification through test of the system. Both material and labor costs are, consequently, high.
In Mueller patent application Ser. No. 09/383,716, there is shown a sealing system that eliminates many drawbacks characteristic of prior art delivery systems, as enumerated in that application, such as, for example, the rotary union, by internally sealing the starter tube by means of a self tightening seal and mounting arrangement therefor. The basis of the arrangement of that application makes use of a constant rotational capability of the seal mounting hub for the self tightening feature.
In all such systems, it is generally the case that the chemical delivery tube is plugged at its distal end which protrudes into the starter tube, and ports are formed in the tube behind the plug, for example, two ports one hundred and eighty degrees apart, for allowing the gas to enter the starter tube interior toward the interior walls thereof, thus creating a radial nozzle. Such an arrangement, which is in widespread use, has the inherent disadvantage of having small port orifices through which all chemicals must be delivered to the starter tube. The ports act as orifice points with the inherent possibility of creating gas expansion problems, such as condensation and pressure drop related issues. The arrangement is non-self purging and does not allow for a complete unobstructed flow of products out of the delivery tube. Further, the plugging of the end of the delivery tube creates a dead zone or eddy volume between the plug and the orifices, where chemicals may become trapped or may pool. Potential contamination in the area (or volume) may build up in the absence of any means of self purging. As a consequence, frequent maintenance of the nozzle end of the delivery tube is necessary. In addition, gas flow exiting the nozzle is non-laminar, and, hence, does not guarantee a uniformity of coating of the interior wall of the starter tube, which is highly desirable.
SUMMARY OF THE INVENTION
The present invention is a dispersion nozzle for affixing to the delivery or distal end of the gas delivery tube, replacing the plug and orifice arrangement common in the prior art.
The nozzle of the invention is roughly conical in shape and has a cylindrical portion or stem extending from the rear or base of the conical portion. The stem is sized to be a press fit into the distal end of the delivery tube, and the nozzle, i.e, cone and stem, has a central bore extending from the rear toward the front (cone tip) of the nozzle. The tip end of the cone is truncated and has an axial bore therein communicating with the central bore, the axial bore having a smaller diameter than the central bore. Also communicating with the central bore are four circumferentially equally spaced, angularly oriented, bores which extend from the sloping face of the cone toward the central bore, such that they intersect. The rear end of the stem, that is, the end of the stem remote from the base of the cone, has an interior chamfer leading into the center bore which provides for a smooth flow of the gas into the bore and out of the angular bores and the axial bore. As a consequence, gases flowing into the central bore are dispersed into the starter tube both axially and radially. The gases within the nozzle flow uniformly without eddying, and, inasmuch as all passages in the nozzle are self purging, no dead zones are formed. The passageways, or bores, formed in the nozzle are sized such that no large pressure drop occurs during the chemical delivery, thereby minimizing any temperature change and likely condensation of the chemicals in the process area. With such an arrangement, flow out of the nozzle is substantially laminar and uniform.
As a consequence of the unique structure and performance of the nozzle of the invention, dead zones and eddies are substantially eliminated and contamination within the nozzle is minimized with a consequent minimization of the necessity for periodic maintenance.
These and other features and advantages of the present invention will be more readily apparent from the following detailed description, read in conjunction with the accompanying drawings.
REFERENCES:
patent: 1408521 (1922-03-01), Lathrop
patent: 2663591 (1953-12-01), Pew
patent: 4278045 (1981-07-01), Ahmad
patent: 5125425 (1992-06-01), Folts et al.
patent: 5826798 (1998-10-01), Schindler et al.
Evans Robin O.
Kashnikow Andres
Lucent Technologies - Inc.
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