US 3325976 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
June 20, 1967 -r 3,325,976
SAMPLE ATOMI ZER Filed April 26, 1966 INVENTOR. C. DAVID WEST id/Km ATTORNEY United States Patent 3,325,976 SAMPLE ATOMIZER Charles David West, Hacienda Heights, Califi, assignor to Beclrman Instruments, Inc., a corporation of California Filed Apr. 26, 1966, Ser. No. 545,500 6 Claims. (Cl. 55-249) This invention relates to sample atomization systems and more particularly to a new and improved ultrasonic atomizer system which is simple and allows rapid and convenient interchange of samples. The sample introduction system disclosed herein may be utilized in many types of spectrochemical analyzers specifically flame photometers, atomic absorption spectrophotometers and emission spectrophotometers and has been utilized advantageously as a sample introduction system for radio frequency plasma emission spectrophotometers. The atomization system may be found useful in any system where an aerosol of a sample is desired.
Although ultrasonic atomization systems have been developed in the past, the atomizer constructed according to the teachings of the present invention provides a reflux system which returns unatomized solution, condensates and larger droplets of the solution immediately to the bulk thereof thus conserving samples. The transducer and sample cup may be temperature stabilized thereby protecting the transducer and avoiding undesirable changes in solution temperature. The present system provides a negligible impedance to gas flow and is constructed and arranged in such a manner that condensed solution will not clog the system. The system provides for rapid changing of the sample and allows positioning of the sample cups in the same geometric relationship to the remaining portion of the system thereby assuring a constant atomization rate from sample to sample. The apparatus requires only 2 to 20 ml. of sample solution and may be readily disassembled and taken apare for cleaning.
The single figure of the drawing illustrates one preferred embodiment of a sample atomization system constructed according to the teachings of this invention.
Referring now to the drawing there is provided a U- shaped support bracket 8 for supporting a sample cup 9 above the face of an ultrasonic transducer 10. The transducer is held firmly in position by a spring clamp 11 affixed by any suitable means to bracket 8. An aperture 13 having a ledge for receiving and supporting sample cup 9 is provided above the center of transducer 10.
Support bracket 8 is affixed to container 14 which may be of any suitable size and provides a container for holding a fluid 15, such as water, which serves the dual function of cooling the ultrasonic transducer and the sample cup and provides a coupling medium therebetween. The container 14 may be provided with a valved inlet and outlet 17 and 18 which may be connected, if desired, to any suitable fluid source to provide a constant flow of fluid through container 14. By providing a constant flow of fluid at a constant temperature the temperature of the sample and the transducer may be readily stabilized. The flowing medium prevents the solution contained in cup 9 from undesired temperature changes. The container 14 may be made of any suitable material such as Lucite and support 8 can be conveniently constructed of aluminum. The sample cup may be constructed of any of a variety of materials, polyethylene being particularly suitable for aqueous solutions.
An atomization cell may be conveniently formed of a hollow cylindrical tube 20 having a removable screw cap 21 threaded thereto. The atomization cell is aflixed within movable arm 23 which is pivotably connected to support bracket 24 at 25. A lever 26 is pivotably afiixed to bracket 24 at 27 and is connected to arm 23 by a linkage 28. As lever 26 is rotated about pivot 27 in the diice rection of the arrow, the atomization cell 20 will be raised slightly by arm 23 allowing removal of sample cup 9. A new sample cup may be placed in support block 8 and the atomization cell again brought in contiguous relation thereto by lever 26 to form a sample compartment in which the sample may be atomized. In the position illustrated the lever may be utilized to lock the sample cell and the atomization cell in gas tight relation to avoid loss of atomized sample. Support bracket 24 and container 14 may be supported on a common plate 29.
Supported within atomization cell 20 is an inverted funnel 30. The maximum diameter of the funnel 30 is slightly less than the inner diameter of the sample cell allowing a restricted area of communication in the form of a toroid betweenthe sample cup 9- and the atomization cell 10. An outlet tube 31 may be supported within cap 21 which provides a conduit for atomized sample to the analyzer which may be a flame, arc, spark, plasma or any other suitable sampling device. The outlet may be provided with a liquid trap which may be conveniently constructed of a bottle 33 with tube 31 entering along one wall thereof thus allowing an area below the end of the outlet tube in which condensate may collect thereby preventing any condensed sample liquid from flowing back into the atomization chamber 20. A drain tube 34 with a pinch clamp for release of the condensed liquid may be utilized if desired. The outlet of bottle 33 is connected to the analyzing system.
In operation the ultrasonic transducer creates a fountain of unatomized solution 35 from which a mist or fog of atomized solution is emitted. Carrier gas flow introduced to tube 36 connected to funnel 30 sweeps this fog rapidly around the sides of the atomization cell and into the outlet tube while allowing the unatomized solution and condensate to be returned rapidly to the bulk of the sample. This reflux system prevents larger droplets of unatomized solution from being introduced into the outlet tube and returns these droplets "to the bulk of the sample thus conserving the sample.
Although not essential it has been found advantageous to construct the atomization cell from a material having a non-wetting property such as Teflon inasmuch as there is less tendency of the atomized solution to condense on the walls thereof. Alternatively, the atomization cell may be conveniently made of a Lucite tubing or of glass coated on its interior surface with a non-wettable material. The tunnel may be of any suitable material but it is advantageous to have the interior surface of the funnel coated with an easily wetted material, and the exterior surface coated with a non-wettable material. A glass tube with a septum cap 38 may be provided for the injection of a sample solution into the atomization cell if desired.
With the atomizer of the present invention the velocity of the carrier gas may be greatly decreased since operation is not dependent upon its velocity past capillary as is the ease with turbulent flow atomizers. The fog or mist is readily and rapidly swept around edges of the funnel into the atomization cell. In practice, the carrier gas may be of any suitable gas such as nitrogen when a plasma torch is utilized or may be the fuel gas or combustion support gas when flame burners are being utilized.
The coupling liquid need not be water and any liquid which serves to couple and cool the transducer and sample cell is suitable. The liquid level may be such that the base of the sample cup is brought into contact therewith. Small amounts of air which might become trapped between the liquid and the base of the cup do not appear to present any problem. However, if problems occur the liquid level may be decreased to about inch below the base of the cup. When the ultrasonic transducer is started a second fountain of coupling solution is created which tends to flush away any trapped air bubbles.
3 There has been illustrated and described a sample atomization system which is simple, may be readily disassembled for ease in cleaning and provides for the rapid interchange of samples. All samples are positioned with the same geometric relationship to the remainder of the system thus assuring a constant rate of sample atomization fromsample to sample. The transducer and sample may be temperature stabilized and there is negligible flow impedance to the carrier gas.
The foregoing disclosure relates only toone preferred embodiment of the invention and numerous modifications and variations are possible in light of the foregoing teachings without departing from the spirit and scope of the invention as set forth in the appended claims.
What is claimed is:
1. A sample atomizing system for atomizing a sample into a carrier gas stream comprising:
a cylindrical sample cup;
a cylindrical atomization cell;
inverted funnel means supported in said cylindrical atomization cell and having a maximum diameter less than said cell to provide a restricted area between said cup and said cell; ultrasonic transducer means; meaning supporting said transducer in operative relation with said cup and including means for containing a coupling medium whereby a fog of atomized sample solution may be created in said sample cup;
means for introducing a carrier gas through said funnel to said sample cup;
carrier gas outlet means from said atomization cell whereby a flow path for said carrier gas is provided from said funnel to said cup through said restricted area and said atomization cell; and
movable means holding said cell contiguous to said cup.
2. The system of claim 1 wherein said cell is constructed of a non-wetting material.
3. The system of claim 1 wherein said movable means holds said cell in gas-tight relation to said cup and wherein said cup is readily removable.
4. The system of claim 1 wherein said cell further included means for introducing a sample directly thereto.
5. An atomizing system for atomizing a solution into a gas stream comprising:
a cup for containing a solution;
an ultrasonic transducer;
means supporting said transducer and said cup in operative relation and providing means for containing a coupling medium therebetween;
atomization cell means contgiuous with said cup;
condensate collecting means supported within said cell means for collecting and returning unatomized solution and condensate to said cup; said condensate collecting means having the same general shape as said cell means over at least a portion of its external surface and being smaller than said cell so as to fit within said cell providing a space between said external surface of said collecting means and the internal surface of said cell for restricting flow from said cup to said atomization cell whereby the flow of unatomized solution and condensate into said atomization cell is limited;
gas inlet means for introducing a flow of gas into said cup; and
gas outlet means connected to said atomization cell means.
6. The system of claim 5 wherein said gas inlet means is formed in said condensate collecting means whereby the gas flows from said condensate collecting means into said cup.
References Cited UNITED STATES PATENTS 3,098,720 7/1963 Nefienger FOREIGN PATENTS 508,582 7/ 1939 Great Britain.
295,784 3/ 1954- Switzerland.
331,265 8/ 1958 Switzerland.
HARRY B. THORNTON, Primary Examiner.
R. R. WEAVER, Assistant Examiner.