Abstract: Isopipes (13) for making a glass or a glass-ceramic using a fusion process are provided. The isopipes are made from an alumina material which has a higher static fatigue than existing alumina materials intended for use as isopipes. In particular, the alumina materials have times-to-failure (static fatigues) of greater than one hour at 1200° C. at an applied stress of 10,000 psi. These high levels of static fatigue allow alumina isopipes to replace zircon isopipes in the manufacture of high performance glass sheets by the fusion process, including glass sheets which are incompatible with zircon isopipes but compatible with alumina isopipes, e.g., chip and scratch resistant glass sheets which have high alkali contents.

Abstract: Methods and apparatus for controlling glass flow in, for example, a downdraw glass manufacturing process (e.g., the fusion downdraw process) are provided. In certain aspects, the mass, thickness, and/or the temperature distribution of molten glass (40) on the surface of forming apparatus (60) is managed by: (A) constructing a stream-tube mapping between (i) regions (510; FIG. 5A) of a cross-section of a conduit (400) that supplies molten glass (40) to the forming apparatus (60) and (ii) regions (510; FIG. 5B) on the exterior surface of the forming apparatus (60); (B) using the stream-tube mapping to select a temperature distribution for the cross-section that results in a desired mass, thickness, and/or temperature distribution of molten glass (40) on the surface of the forming apparatus (60); and (C) heating and/or insulating the conduit (400) so as to produce a temperature distribution for the cross-section which equals or at least approximates the distribution selected in step (B).

Abstract: Isopipes (13) for making a glass or a glass-ceramic using a fusion process are provided. The isopipes are made from an alumina material which has a higher static fatigue than existing alumina materials intended for use as isopipes. In particular, the alumina materials have times-to-failure (static fatigues) of greater than one hour at 1200° C. at an applied stress of 10,000 psi. These high levels of static fatigue allow alumina isopipes to replace zircon isopipes in the manufacture of high performance glass sheets by the fusion process, including glass sheets which are incompatible with zircon isopipes but compatible with alumina isopipes, e.g., chip and scratch resistant glass sheets which have high alkali contents.

Abstract: Methods and apparatus for controlling glass flow in, for example, a downdraw glass manufacturing process (e.g., the fusion downdraw process) are provided. In certain aspects, the mass, thickness, and/or the temperature distribution of molten glass (40) on the surface of forming apparatus (60) is managed by: (A) constructing a stream-tube mapping between (i) regions (510; FIG. 5A) of a cross-section of a conduit (400) that supplies molten glass (40) to the forming apparatus (60) and (ii) regions (510; FIG. 5B) on the exterior surface of the forming apparatus (60); (B) using the stream-tube mapping to select a temperature distribution for the cross-section that results in a desired mass, thickness, and/or temperature distribution of molten glass (40) on the surface of the forming apparatus (60); and (C) heating and/or insulating the conduit (400) so as to produce a temperature distribution for the cross-section which equals or at least approximates the distribution selected in step (B).