Acoustic bubble removal method

• US 4,398,925 A
• Filed: 01/21/1982
• Issued: 08/16/1983
• Est. Priority Date: 01/21/1982
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Wang, Taylor G., Elleman, Daniel D., Trinh, Eugene H.
• Primary Examiner(s): LACEY, DAVID LYNN
• Application Number:
  US06/341,406
• Time in Patent Office: 572 Days
• Field of Search: 55/15, 55/87, 55/178, 55/277, 55/36, 55/38, 55/52, 65/134, 366/114, 210/748, 252/361
• US Class Current: 95/30
• CPC Class Codes: B01D 19/0078 by vibration
• CPC Class Codes: C03B 5/225 Refining C03B5/18 takes precedence ; Refining agents C03C1/004

Abstract

A method is described for removing bubbles (14) from a liquid bath (12), such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension (H) to drive the larger bubbles toward a pressure well (30) where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles (50) are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid (16).

Claims

1. A method for removing gas bubbles, including larger bubbles and smaller bubbles, from a bath of liquid, comprising:

first removing the larger bubbles by applying acoustic energy of a mode which is resonant to a bath dimension to drive bubbles toward a pressure well of the mode to at least partially coalesce them so as to form the larger bubbles, and then removing the coalesced larger bubbles;

thereafter dissolving the smaller bubbles that remain in the liquid of the bath, by applying acoustic energy of frequencies which are resonant to the smaller bubbles to create bubble oscillations and consequent microscopic stirring of liquid immediately around the smaller bubbles.

2. The method described in claim 1 wherein:

said step of dissolving includes applying a variable frequency which is swept through a frequency range wherein the highest frequency is more than ten times the lowest frequency.

3. The method described in claim 1 wherein:

said step of applying acoustic energy of frequencies which are resonant to the smaller bubbles includes applying acoustic energy within a range of frequencies which resonate bubbles in said liquid lying in the range of diameters of 50 microns to 1000 microns.

4. The method described in claim 1 wherein:

said step of applying acoustic energy resonant to a bath dimension includes applying a succession of different modes resonant to the bath dimensions, with successive modes having pressure wells progressively closer to a surface of said bath.

5. A method for removing gas bubbles from a bath of liquid which has at least a predetermined surface comprising:

applying acoustic energy of successive modes which are each resonant to a dimension of the bath, to drive bubbles toward pressure wells of the modes, with successive modes having pressure wells progressively closer to said predetermined surface of said bath, whereby to establish a zone extending through most of the bath that is free of large bubbles.

6. The method described in claim 5 wherein:

said predetermined surface to which the pressure wells of successive modes are progressively closer faces a gaseous environment.

7. A method for dissolving gas bubbles of predetermined size in a bath of liquid of known density and viscosity in which the bubbles lie, comprising:

applying acoustic energy to said liquid bath of a frequency that is resonant to said bubbles so as to cause bubble oscillations and consequent microscopic stirring of the liquid immediately around the bubbles which causes gas in the bubbles to dissolve in the liquid.

8. The method described in claim 7 wherein:

said bubbles vary in size and said step of applying includes varying the frequency of said acoustic energy over a frequency range wherein the highest frequency is more than ten times the lowest.

9. The method described in claim 8 wherein:

said bath contains bubbles of a size between about 50 microns and 1000 microns diameter in a quantity that significantly affects the utility of said bath, and the lowest frequency is about 0.5 kHz and the highest is about 40 kHz whereby to remove bubbles in a range of diameters of about 50 microns to 1000 microns.

10. The method described in claim 7 wherein:

said step of applying acoustic energy includes modulating a high frequency electrical signal with a lower second signal of said frequency which is resonant to said bubbles.