Patent ID: 7451621
Filing Date: 2008-11-18
Classification: C03B

Abstract:
1. A method for forming a plurality of streams of non-coalescing bubbles of helium in molten glass, wherein each bubble in a given stream is of substantially the same size, comprising: (A) providing a tank that contains molten glass; (B) providing two or more passageways through the tank each of which terminates in an upward facing opening that is in fluid communication with said molten glass in said tank below the upper surface of said molten glass; (C) providing a common gas supply line and a helium source which supplies gaseous helium at pressure to said common gas supply line; (D) providing gas feed lines each of which is in fluid communication with said gas supply line and with a different one of said passageways, and providing in each gas feed line a gas-permeable restriction so helium passing from said gas supply line to a passageway must pass through a gas-permeable restriction into the space between the restriction and the opening at the end of said passageway, wherein the pressure drop across said restriction is high enough and the volume of said space is large enough that non-coalescing bubbles of helium are produced from the end of said passageway into said molten glass; and (E) providing helium from said source into said gas supply line, wherein said helium passes into said gas feed lines through the restrictions associated therewith and said helium accumulates in said spaces and increases in pressure in said spaces while bubbles of helium begin to form at the openings at the ends of said passageways, and said helium intermittently detaches from the openings at the ends of said passageways as bubbles whose size is a function of the volume of said space, and (F) adjusting the pressure in said gas supply line so that said bubbles are spaced apart by at least half a bubble diameter.