Composite threshold assembly for a molten glass delivery apparatus and method of delivery
AssigneePPG Industries, Inc.
InventorRobert L. Tilton
Life of this patent
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Abstract
A glass delivery facility connecting a glassmaking furnace with a molten metal-containing glass forming chamber employs a threshold assembly having a front face base block having a foot which extends downstream from the threshold-molten metal interface beneath the molten metal and having a transverse subsurface gap for directing gases from the molten metal to the sides of delivery facility so that gas bubbles are removed to avoid deformation of the underside of flat glass being produced.
Claims10
In a molten glass delivery apparatus connecting a glassmaking furnace to a glass forming chamber which contains a pool of molten metal for supporting glass during forming comprising a glass-supporting threshold extending across the width of an inlet end of the forming chamber, side members, a roof and a metering member extending downwardly between the side members to provide a controllably sized opening defined by the metering member, the side members and the threshold through which molten glass may be delivered from the glassmaking furnace onto the molten metal in the forming chamber, wherein the threshold comprises a plurality of refractory pieces and has an upwardly-facing, convex upper surface for supporting molten glass during delivery that includes a front face extending beneath the surface of the pool of molten metal in the forming chamber whereby molten glass is provided support until it is supported by the molten metal, the improvement which comprises
- a threshold for delivering molten glass from the furnace to the forming chamber including an upper refractory portion of substantially impervious fused refractory having a glass-supporting surface that extends in a slope downwardly from the top of the threshold into contact with the molten metal in the forming chamber and
- a lower refractory portion positioned below and supporting said upper portion, said upper and lower portions having spaced opposing surfaces forming a gas collecting recess which terminates in a transverse opening extending along the front face of the threshold beneath the surface of the pool of molten metal for collecting gases present therein,
- means for venting gases from said transverse opening, and
- means for preventing the flow of molten metal about the ends of the threshold into said transverse opening.
In a method of making flat glass wherein a stream of molten glass is delivered over a refractory, glass-supporting threshold extending across the width of an inlet end of a forming chamber from a glassmaking furnace onto the surface of a pool of molten metal in the forming chamber while maintaining support of the glass and thereafter forming a continuous dimensionally stable sheet of glass by cooling and advancing the delivery glass, the improvement which comprises
- directing gas present in the molten metal in the vicinity of molten glass delivery along a gas collecting opening extending beneath the refractory supported molten glass from a region below the surface of the pool of molten metal to a region above the surface of the pool of molten metal,
- venting the gas from the region of the opening beneath the refractory supported molten glass which is above the surface of the pool of molten metal, whereby the incidence of scattered deformations in the bottom surface of the glass being made is substantially diminished, and
- preventing the flow of molten metal about ends of the threshold into the gas collecting opening.
Dependencies are inferred from the claim text.