Method of adjusting glass temperature in a forehearth

• US 4,029,488 A
• Filed: 08/02/1976
• Issued: 06/14/1977
• Est. Priority Date: 08/02/1976
• Status: Expired due to Term

• Current Assignee: VHC Ltd.
• Original Assignee: C Rhett Incorporated
• Inventors: Rhett, Chester K.
• Primary Examiner(s): Kellogg, Arthur D.
• Application Number:
  US05/711,068
• Time in Patent Office: 316 Days
• Field of Search: 65/134, 65/135, 65/136
• US Class Current: 65/135.3
• CPC Class Codes: C03B 7/06 Means for thermal conditioning or controlling the temperature of the glass

Abstract

The temperature of molten glass conveyed by means of a forehearth between a melting furnace and a discharge orifice in a bowl remote from the furnace is controlled and adjusted thermally by a method that includes an abrupt bottom-zone temperature reduction step in the immediate proximity of the entry of the glass from the furnace to the forehearth cooling zone to a temperature approximately equal to but above a predetermined gob temperature; next the step of blending and homogenizing the cooling glass as it enters the conditioning zone in its downstream movement; and while avoiding above-surface heating during conditioning, subjecting the glass stream only to mild Joule-effect, below-surface heating applied in a controlled manner to accomplish temperature normalization and homogeneity throughout the stream whereupon the glass is delivered to the discharge orifice at a specified temperature.

Claims

1. The method of delivering molten glass at a predetermined gob temperature from a melting furnace to an orificed forehearth bowl, comprising:

1. in the forehearth in close proximity to the entry of molten glass from said furnace, abruptly reducing the temperature of a lower central portion of the glass stream to a temperature approximately equal to but above the predetermined gob temperature;

2. immediately following the temperature reduction, mechanically blending and homogenizing the glass as it moves downstream;

3. continually applying a mild Joule-effect, below-surface conditioning heat to said stream for a period of time at least twice the length of time said stream was subjected to abrupt temperature reduction and permitting downward temperature adjustment to substantially the predetermined gob withdrawal temperature accompanied by temperature normalization throughout the stream; and

4. discharging the glass through the orifice of said bowl in the form of a series of uniform gobs.

2. The method of conditioning a stream of molten glass in a forehearth in the absence of above-surface heating of the glass as it flows downstream from a furnace toward a bowl having an orifice for glass gob withdrawal at a predetermined temperature, comprising:

1. establishing a continuously moving stream of molten glass flowing through a forehearth between a melting furnace and a forehearth bowl;

2. abruptly reducing from below the surface the temperature in the central zone of the molten glass stream proximate its entry to the forehearth from the furnace to a temperature approximately equal to but above the preferred gob withdrawal temperature;

3. mechanically blending and homogenizing the flowing temperature-reduced stream of molten glass as it moves downstream away from the furnace;

4. subjecting the mechanically blended and substantially homogenized stream of molten glass solely to mild Joule-effect, below-surface conditioning heat for a period of time, at least twice the length of time said stream of molten glass was subjected to abrupt temperature reduction and, during said longer time period, accomplishing downward temperature adjustment to substantially the predetermined gob withdrawal temperature to accomplish temperature normalization throughout the stream; and

5. discharging the glass through said bowl orifice in the form of a continuous series of uniform gobs.

3. The method of claim 2 in which, proximate the entry of the glass to the forehearth bowl, the stream of molten glass is subject to mechanical blending and homogenizing.