Process of producing glass

摘要

In a process for producing glass in sheet or ribbon form wherein the glass is floated at a temperature at which it will flow upon a liquid having a density greater than that of the glass, the floating glass naturally tending to attain an equilibrium thickness, an area of the upper surface of the glass within its edges is subjected to a pressure, and the liquid outside of or in contact with the glass is subjected to a different pressure, thereby controlling the thickness of the glass within the edges thereof so as to be different from said equilibrium thickness. The apparatus for effecting this process is very similar to that described in Specification 1,019,752 for screening at least one portion of the glass from another by discharging a gas stream towards the ribbon, except that a seal 100, covering the whole of the lower face of wall 40 and designed to apply the gas pressure to the specified areas comprises a plurality of individually supplied pressure zones in the form of modules of rectangular configuration lying in a common plane, successive rows crossing the intended path of travel of the ribbon and the rows being at an angle to the direction of travel. Each module is divided into four chambers 100a-100b supplied with a preheated inert gas under pressure from chamber 105 through stem 104 and passageways 102. The gas issues forth at an evenly distributed pressure over the face of the module, and exhausts between adjacent modules into passages 107. In a further embodiment, Figs. 25-28 (not shown), a bed of modules 1001, similar to modules 100, overlie, and are in close proximity to, the entire width of the ribbon, except for marginal edges along the side. By the use of these individual pressure modules it is possible to obtain a glass ribbon of a thickness varying from the equilibrium thickness, and also of a thickness which may vary across the width of the ribbon. It is possible to make the glass ribbon displace more than its own weight of liquid metal (e.g. molten tin or alloy). A further type of fluid seal described is one using a liquid less dense than the glass but immiscible with glass or metal, e.g. molten alkali metal salts. Reference has been directed by the Comptroller to Specification 769,692.