AU5398501A - Apparatus for reducing friction between two vessels - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Icon Dynamics, LLC Actual Inventor(s): Donald B Rodgers Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: APPARATUS FOR REDUCING FRICTION BETWEEN TWO VESSELS Our Ref POF Code: 646083 1443/369179 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- APPARATUS FOR REDUCING FRICTION BETWEEN TWO VESSELS The present application is a divisional application from Australian patent application number 62726/98, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to an apparatus for reducing friction between two vessels, and has particular but not exclusive application to systems for maintaining a generally constant level of fluid within a vessel and more particularly to systems for supplying vapor to a chemical process by introducing a carrier gas into a fluid column of vaporizable liquid.

Background Information A technique used in vapor generating systems for delivering chemical vapor to a process chamber is to force a carrier gas bubble through a chemical fluid in a bubbler and then to deliver the resulting vapor from the bubbler to the process chamber. Traditional bubblers, including those utilized in presently available automatic refill systems, rely on relatively large fluid volumes to **intrinsically compensate for deviations in fluid level which can negatively effect the resulting vapor concentration. Since vapor sources in the fiber optics and semiconductor industries are often hazardous fluids, there has been an increasing focus on the occupational safety and health concerns resulting from use of such fluids. This has resulted in reducing the maximum allowable volumes of many of these fluids within the work place. It is therefore desirable to reduce the required fluid volume at the point of vapor generation without compromising vapor concentration control.

:Typically a bubbler container is comprised of a single vessel which holds an expendable volume of vaporizable fluid. A carrier gas such as hydrogen, helium or nitrogen is introduced at the lower level of a fluid column, travels up through, and exits the fluid surface into a head space. As the carrier gas passes through the fluid column it becomes entrained with vapor which results in a corresponding reduction of the fluid volume. This reduction of the fluid Y:\Species\62726amenddiv.doc level in the bubbler container may be significant for several reasons. For example, the vaporization efficiency and overall vapor concentration uniformity are both affected by the fluid level and are both important elements which may affect the strict tolerance requirements of the process application. In addition, the physical fluid column in the bubbler not only determines the carrier gas contact time and resulting bubble geometry but also represents the mass to which thermal energy is either added or extracted. It also defines the head space present above and within the bubbler container which has been found to negatively effect the vapor concentration and ultimate bubbler performance when not optimized.

Inasmuch as vapor extraction from a fluid volume results in depleting the fluid volume of a bubbler, causing variations in vapor concentration, a means of replenishing this fluid is desirable. Some methods include manually replacing the bubbler ampule once the volume of fluid reaches a predetermined minimum acceptable level. Other manual 20 methods rely on an auxiliary supply of fluid to replenish the bubbler during intermittent periods of non-use. Although such methods can result in reducing many of the concerns associated with prior art expendable bubblers, such as o reducing the risk of contamination during ampule replacement or any necessary fluid replenishment, these systems typically remain idle until an interruption in vapor extraction provides a refill opportunity. With many of the advanced processes running for long periods of time before a refill opportunity is presented, the fluid level may descend oooo• S" 30 considerably resulting in less than optimum vapor delivery efficiency. Although there are techniques which can be employed to compensate for the influences of a constantly descending fluid volume, such as intermittent refill in between process runs, such techniques can be complex and costly.

4 In addition to manual replenishment of fluid, automatic bubbler refill systems are also available. However, such systems typically employ float coupled electronic devices, such as level controllers, to control the replenishment of fluid in the bubbler. Such devices are prone to failure and are generally the most common failure mechanism in the system. Other types of fluid level sensors such as optical, load cell monitoring of the contents, and resistance probe have been employed. However, the use of such devices can be costly, prone to error, and with many of the fluids being flammable, represent ignition sources if not properly rated and maintained.

Co-pending Australian Patent Application No. 62726/98 (from which the present application has been divided) provides an apparatus and method which can maintain a nearly constant liquid level, which uses a float vessel disposed within a primary containment vessel, as is further described in that application.

Summary of the Invention The present invention has as an aim the prevention or reduction in wear effects or particle generation from friction between inner and outer vessels, as **"for example used in the above-mentioned co-pending application, and, viewed from a first aspect, provides an apparatus for reducing friction between two **vessels including: an outer vessel having an inner chamber, an inner vessel disposed within said chamber, m a first inner vessel magnet disposed at one end of said inner vessel and proximate to at least one first outer vessel magnet having an opposing magnetic field, a second inner vessel magnet disposed at an opposite end of said first inner vessel magnet, a plurality of second outer vessel magnets positioned in proximity to and having opposing magnetic fields to said second inner vessel magnet whereby opposing magnetic fields of said inner and outer magnets are employed to maintain concentric suspension of said inner vessel.

The present invention thus reduces wear effects or particle generation from friction by the use of magnetic forces, and is particularly useful when the inner and outer vessels are used in a self-metering reservoir for use in vapor generating systems, wherein the inner vessel is a bubbler vessel in which a carrier gas is passed through a vaporizable liquid and wherein the liquid is y:\Species\62726amenddiv.doc metered into the bubbler vessel through relative movement of the inner and outer vessels.

The magnetic fields may be adjustable to compensate for fluids of different specific gravities, and the use of magnetic fields reduces the possibility of particulate contamination otherwise resulting from surface abrasion at the contact points of moving parts within the bubbler.

The present invention may also provide a means of calibrating the buoyant interaction of the inner bubbler vessel relative to different fluid applications and more specifically to differences in specific gravity through the use of opposing magnetic fields, one fixed within the inner buoyant bubbler vessel and one which can be adjusted at the base of the outer vessel.

o* oooo* Y:\Species\62726amenddiv.doc BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front face cutaway illustration of a bubbler container assembly in accordance with the present invention.

FIG. 2 is an isometric cutaway illustration of the bubbler container assembly.

FIG. 3 is a diagrammatic illustration of a bubbler container assembly depicted within a basic operational control scheme.

DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENTS

The following description is of the best presently contemplated modes of carrying out the invention in the context of a bubbler container assembly. This 20 description is not to be taken in a limiting sense but is made merely for the purpose of describing the principles of the invention.

The description herein presented refers to the accompanying drawings in which like reference numerals refer S to like parts throughout the several views. Figure 1 is an illustration depicting an assembly of elements comprising the bubbler. During operation, the bubbler assembly operates as a float coupled metering device which supports the generation of vapor from a vaporizable fluid contained within the float ooo ~vessel. Among the major elements depicted in FIG. 1 are the 30 primary containment vessel 5 and the inner bubbler float vessel 6. A carrier gas, supplied and controlled externally, connects to port 2 through fitting 24, travels through the conduit 8 and exits into the lower level of the vaporizable fluid present within the inner float vessel 6. As the carrier gas travels up through the fluid it becomes entrained with vapor, exits the fluid surface into the head space and exits discharge port 3 through fitting 25. As a result of vapor generation, the fluid level of the inner float vessel 6 descends. This action results in reducing the weight of the inner float vessel 6 which is otherwise suspended within the fluid of the outer vessel 5. As a function of weight loss, the inner float vessel 6 gains buoyancy and ascends within the makeup fluid chamber 22 of the outer vessel 5. The upward buoyant movement of the inner vessel 6 withdraws metering stem tip 10 from aperture which is shown in FIG. 2. This action meters a corresponding makeup fluid flow into the makeup fluid chamber 22 from an externally supplied source connected to port 1I and fitting 23. As the makeup fluid level rises within the makeup fluid chamber 22 of outer vessel 5, the inner float vessel 6 continues to travel upward. In the preferred embodiments shown in FIG. 1 and FIG. 2, the magnets 14 are encased by fittings 15 in each of the four corners of the upper portion of the outer vessel 5. The rising inner float vessel 6 is increasingly repelled by the flux fields of magnet 16 as it ascends into the flux fields of magnets. 14. At a point when 20 the repelling force exceeds the buoyant lift of the inner float vessel 6, makeup fluid in the outer vessel 5 reaches and cascades into the inner float vessel 6 through holes 9.

The introduction of makeup fluid into the inner float vessel *o:o 6 increases its weight causing it and metering tip 10 to descend into aperture 10a restricting the makeup flow rate.

During operation, the extraction of fluid from the inner float vessel 6 by means of evaporation results in lowering oooo the energy level of the fluid volume. This thermal energy loss is a function of the latent heat of vaporization for the 0@ 30 fluid being evaporated and the extraction rate of fluid per unit time. The fluid temperature within the bubbler may be controlled and monitored by standard industrial thermoelectric temperature control modules 27, such as that sold by Melcor Corporation as part number CP1.0-127-051-2 and a thermal well 7 filled with oil and incorporating a temperature sensing thermocouple, such as that sold by Simpson as Type 21244, Sensor Type RTD. The thermoelectric 8 temperature control module power leads 29 and temperature probe sensor leads 4 integrate by means of standard industrial practice to a programmable temperature controller 32, shown in FIG. 3. Aluminum plates 26 fastened to the exterior walls. of the outer vessel 5 increase the thermal exchange rate between the thermoelectric converters 27 and the fluid volume in the outer vessel 5. Commercially available convection type heat transfer fins 28, such as those sold by Melcor Corporation, are placed on the outer faces of the thermoelectric converters 27 to increase the thermal exchange rate efficiency of the temperature control unit. These elements are incorporated so as to provide ampule thermal capacity as dictated by the amount of fluid to be evaporated per unit time and the fluid's latent heat of vaporization.

The dry weight of the inner vessel 6 is compensated for by the repelling forces of the opposing fields of the inner vessel disc magnet 11 and the outer vessel ring magnet 12.

Because the invention is intended to be utilized with many 20 different fluid types, compensating for fluid characteristics such as specific gravity and viscosity is accomplished by setting the distance between the outer vessel ring magnet 12 and the inner vessel disc magnet 11. This adjustment-is accomplished by turning the outer vessel magnet backup ring 13 which is threaded into the base of the outer vessel 5. In function, an otherwise dry inner vessel 6 is dynamically suspended just above its fully seated position within the o*o.

outer vessel metering aperture 10a. This results in reducing the metered influx of a makeup fluid entering the outer 30 vessel to a point less than the lowest possible evaporation o°*.rate during the introduction of a carrier gas. Isolation valves incorporated within the supply stream of the fluid makeup, carrier gas inlet, and vapor delivery lines work as a group and are either open or closed as a group thereby totally isolating the invention when vapor is not needed.

Optimum functionality of the preferred embodiments are dependent upon the strength of the magnetic fields. For this reason, rare earth magnets such as the type sold by Master Magnetics, Inc. as Samarium Cobalt are preferred to satisfy the various shapes noted as magnets 11, 12, 14, and 16.

Because the invention is intended to handle fluids that must be contamination free and specifically free of byproducts resulting from a reaction between the fluid and the magnetic material, magnets 11 and 16 should be fully encased in the same material as that of the inner and outer bubbler vessels.

FIG. 3 depicts a diagrammatic illustration of the vapor generation system. Representative are the reservoir fluid level 30, and inner bubbler vessel fluid level 31, as a carrier gas is introduced through conduit 2, exits into and travels up through the inner vessel bubbler fluid contained therein and is converted to a vapor state. This action reduces the amount of fluid contained within the inner bubbler vessel 6. The resulting loss of fluid within the inner bubbler vessel 6, as fluid is converted to vapor, reduces its total weight resulting in an increase in S. buoyancy; the total dry mass of the inner vessel 6 in 20 conjunction with a preferred minimum volume of fluid therein result in a fully seated state with respect to the position of the metering stem tip 10 and the fluid makeup aperture Although absolute isolation of makeup fluid being introduced into the reservoir is not intended, in the fully 25 seated state, the influx rate of makeup fluid is far below the lowest possible liquid to vapor conversion rate under any normal state of operation. To insure that the reservoir .cannot become overfilled with fluid, independent isolation of the fluid makeup source through port 1 and the carrier gas 30 source through port 2 is included. As seen in FIG. 3, representative industrial standard valves, such as that sold by Nupro-Swagelok, Co. as part number SS-BNV51-C are used for positive isolation of the inlet ports 1 and 2, and outlet port 3. In the preferred embodiments, all three valves, 34, 35, and 36, are of the normally closed automatic type. As represented in FIG. 3, control signals to each of the valves would originate from a control system 33. This control system would most likely be part of the overall process automation platform controlling all the devices necessary to support the vapor deposition application.

It should be understood that the embodiments described herein merely illustrate principles of the invention in selected preferred forms. Many modifications, additions and deletions may, of course, be made thereto without departure from the spirit and scope of the invention as set forth in the following claims.

S. S

Claims (4)

1. An apparatus for reducing friction between two vessels including: an outer vessel having an inner chamber, an inner vessel disposed within said chamber, a first inner vessel magnet disposed at one end of said inner vessel and proximate to at least one first outer vessel magnet having an opposing magnetic field, a second inner vessel magnet disposed at an opposite end of said first inner vessel magnet, a plurality of second outer vessel magnets positioned in proximity to and having opposing magnetic fields to said second inner vessel magnet whereby opposing magnetic fields of said inner and outer magnets are employed to maintain concentric suspension of said inner vessel.

2. The apparatus according to claim 1 wherein a distance between said first *°,inner vessel magnet and said first outer vessel magnet may be adjusted to Goof compensate for different weights of fluids to be contained within said vessels. C. Ce *°oO o o

3. The apparatus according' to claim 1 or 2 wherein said first outer vessel magnet is a ring magnet. 6 ,god o CoCo

4. The apparatus according to claim 1, 2 or 3 wherein said first inner vessel magnet is a disk magnet. C 900 The apparatus according to any one of claims 1 to 4 wherein said second inner vessel magnet is centered within the flux fields of said plurality of second outer vessel magnets. DATED: 21 June 2001 PHILLIPS ORMONDE FITZPATRICK Attorneys for: ICON DYNAMICS, LLC Y:\Species\82726amenddiv.doc