Overflow downdraw glass forming method and apparatus

摘要

The present invention discloses improved methods and apparatus for forming sheet glass. In one embodiment, the invention introduces a counteracting force to the stresses on the forming structure in a manner such that the thermal creep which inevitably occurs has a minimum impact on the glass flow characteristics of the forming structure.

主权项

1. A method for forming a glass sheet using an improved apparatus, wherein the apparatus includes a trough for receiving molten glass that has sides attached to a wedged shaped sheet forming structure that has downwardly sloping sides converging at the bottom of the wedge such that a glass sheet is formed when molten glass flows over the sides of the trough, down the downwardly sloping sides of the wedged shaped sheet forming structure and meets at the bottom of the wedge, and wherein the method comprises the steps of:
(a) providing at least one inlet end compression block located at an inlet end of the forming structure, wherein the inlet end compression block is positioned at a bottom end of the forming structure; (b) providing at least one far end compression block located at an opposite end of the forming structure as the inlet end compression block, wherein the far end compression block is positioned at the bottom end of the forming structure; (c) applying an inlet end force with an inlet end force applicator to the inlet end compression block such that a bottom of the inlet end of the forming structure is deformed, by thermal creep, in a longitudinal direction; and (d) applying a far end force with a first far end force applicator to the far end compression block such that a bottom of the far end of the forming structure is deformed, by thermal creep, in a longitudinal direction; wherein the force applicators apply forces in opposite longitudinal directions to the respective compression blocks such that the bottom of the forming structure is in substantially greater compression than the top of the forming structure such that the bottom of the forming structure, which has a greater resistance to thermal creep than the top of the forming structure, is deformed longitudinally by thermal creep the same magnitude as the top of the forming structure; wherein the inlet end force applicator and the first far end force applicator consistently apply the corresponding inlet and far end forces to remain at a desired level throughout a production campaign such that the bottom of the forming structure deforms under thermal creep by the same magnitude as the top of the forming structure deforms under thermal creep, wherein any deformation of the forming structure that results from thermal creep has a minimal effect on a thickness variation of the glass sheet.