US 4,133,666 A · Method and apparatus for making variegated glass in a continuous sheet

Abstract

At least two differently colored components of glass are heated to a molten, viscous state and then combined in a channel shaped forehearth to form a confluent of molten glass in which the starting components remain in discrete domains, delineated by abrupt color transitions at the interfaces between such domains. The confluent flows by gravity to a discharge end of the forehearth, at which the molten glass is fed between a pair of forming rollers which press it into a continuous, elongate sheet of variegated glass. While flowing toward the discharge end of the forehearth, the molten glass is subjected to controlled, limited stirring to break up relatively large domains of homogeneous color into a multitude of smaller randomly dispersed domains characterized by streaks, swirls and waves of individually identifiable colors. A first, coarse stirring operation is performed at a location substantially upstream of the discharge end of the forehearth and consists of reciprocating a stirring paddle in a cross-channel path and thus transverse to the direction of flow of the molten glass. Downstream therefrom, gas bubbles are injected into the confluent, from the bottom of the forehearth channel, and these bubbles migrate upwardly through the viscous, molten glass, agitating, stirring and thus further dispersing the individual color domains. Finally, a second, fine stirring operation is carried out immediately adjacent the discharge end of the forehearth by manipulating another stirring paddle in a non-synchronous mixing pattern, including up and down and transverse stirring strokes which impart a final, esthetic randomness to the color domains in the glass. Adjacent the discharge end of the forehearth, the flow of molten glass is partially obstructed by a shallow weir, over which the glass flows to reach the forming rollers, and behind which a reservoir of molten glass develops to provide a source of supplemental quantities of glass, which is used as needed to compensate for transient shortfalls in the quantity of glass reaching the forming rollers.

Claims17

Dependent claims

A process for making variegated glass in continuous sheet form, comprising:

heating first and second components of glass of different preselected colors, to a molten state;
introducing said components of glass into a channel shaped forehearth and establishing a "plug" flow of said components toward a discharge end of said forehearth, said "plug" flow being an unblended confluent of said first and second components of glass while in said molten state wherein said components remain in discrete domains having substantially abrupt transitions in color at the interfaces between such domains;
stirring said confluent as it flows in said forehearth so as to break up and disperse said domains throughout the volume of said confluent while maintaining said substantially abrupt transitions in color between said domains;
flowing said confluent over a weir, located at the discharge end of said forehearth, into a feed side of a pair of forming rollers which press the confluent of glass into the shape of a continuously elongate sheet;
adjusting the volumetric flow rate of said confluent by so metering the rate of introduction of said components into said forehearth and by so inclining said channel shaped forehearth so that said flow rate is just sufficient to supply enough molten glass at the discharge end of the forehearth for enabling the forming rollers to produce said sheet with a substantially uniform predetermined width, without causing a buildup of excessive molten glass at the feed side of said rollers;
and
supplementing the volume of said confluent of molten glass that flows naturally, by gravity over said weir and to the feed side of said forming rollers with supplementary quantities of molten glass taken from a reservoir of said confluent of glass that develops on the upstream side of said weir in order to alleviate transient shortfalls of said confluent at the feed side of said rollers, wherein said transient shortfalls occur as a result of unsteady flow of said confluent due to frictional effects in conjunction with said step of adjusting the volumetric flow rate of said confluent to be just sufficient to supply said forming rollers.

4 more elements

A process for making variegated glass in continuous sheet form, comprising:

heating first and second components of glass of different, preselected colors to a molten state;
introducing said components of glass while in said molten state into a first end of a forehearth channel and flowing said molten glass as a confluent of said first and second components toward a discharge end of said forehearth channel, wherein said components remain in discrete domains of homogeneous color;
establishing a "plug" flow of said confluent in said forehearth channel by shaping, dimensioning and inclining said channel so that said confluent of molten glass has a substantially uniform velocity profile across said channel;
stirring said confluent as it flows in said forehearth channel to cause limited, controlled mixing of said first and second components of glass while maintaining said domains of homogeneous color;
and
forming said partially mixed confluent into a continuously elongate sheet of glass by feeding the stirred confluent over a weir oriented across said channel at said discharge end thereof and into the feed side of a pair of forming rollers which receive and press said confluent into said sheet.

3 more elements

In an apparatus for producing variegated glass in continuous elongate sheet form and including a channel shaped forehearth into which molten glass prepared from at least first and second differently colored glass components is introduced at a receiving end of said forehearth and the confluent thereof is caused to flow by gravity toward a discharge end of said forehearth at which forming rollers receive the molten glass and press it into a continuous elongate sheet of glass having a predetermined minimum width, wherein the improvement comprises:

said forehearth having a width that is substantially less than said predetermined width of said sheet at locations upstream of said discharge end and being inclined downwardly in the direction of flow and being divergent in the direction of flow at a location adjacent said discharge end so that the flow of said confluent widens to match said predetermined minimum width of said sheet as said confluent passes through said forming rollers;
structural means disposed in said channel shaped forehearth adjacent said discharge end forming a cross-channel weir of preselected height, over which the confluent of molten glass must flow to reach said forming rollers;
and
means for stirring the confluent of molten glass while in said forehearth, said means for stirring being disposed upstream of said structural means forming said weir.

1 more element

Dependencies are inferred from the claim text.

Method and apparatus for making variegated glass in a continuous sheet

Life of this patent

Method and apparatus for making variegated glass in a continuous sheet

Life of this patent

Abstract

Claims17