MANUFACTURE OF FLOAT GLASS OF A THICKNESS GREATER

专利名称：MANUFACTURE OF FLOAT GLASS OF A

THICKNESS GREATER THAN EQUILIBRIUMTHICKNESS

发明人：JOSEPH A. GULOTTA申请号：US3432284D申请日：19670410公开号：US3432284A公开日：19690311

摘要： In the production of sheet glass in the form of a layer using the \"float\"technique the width and thickness of the layer are substantially stabilized at the

dimensions attained during contact with side walls of the bath. The apparatus is the sameas that disclosed in Specifications 1,019,752 and 1,019,753. A layer of molten glass isdelivered from a spout on to a bath of molten tin or tin alloy and is allowed to spreadout into wetted contact with diverging side walls 19a, 19b of the bath. Whilst in contactwith the side walls 19a, 19b the molten layer passes beneath the front depending wall ofthe bath roof into tank 18. This is divided into two zones 25c and 28b by a circumferentialwall 40 depending from the roof. Inert gas under pressure is fed to each zone betweenwhich a pressure differential may be maintained. Non-wetting inserts, e.g. graphite, 21a,21b are placed at the downstream terminal end of the side walls to facilitate freeing ofthe molten layer from contact with the side walls at its predetermined width and

thickness. The layer then passes along the length of the bath and is cooled progressivelyso as to be removed unburned. The gaseous pressures above the layer in zones 28c and28b is adjusted so as to maintain the width and thickness of the layer. In an alternative

embodiment the pressure zones are replaced by a bi-level bath, the central bath 214a(Fig. 13) being separated from side baths 214b by upstanding graphite walls 224, 225. Thetraction on the cold end of the formed sheet may be controlled with the rate of flow onto the bath to control the sheet thickness at, above, or below equilibrium thickness.Various modifications of the divergent side walls are given particularly with reference toFigs. 8 to 11 (not shown) in which the length and shape of the side walls is modified; andthe graphite inserts may be omitted. When the glass layer leaves contact with the sidewalls 19a, 19b its temperature is still above 1500 DEG F. An inert atmosphere ismaintained above the molten metal bath. After leaving contact with the side walls thewidth or thickness of the sheet may be altered slightly, such as by the application of atractive force or by supporting the central portion at a higher level or applying a greaterpressure to that portion than the surrounding portions. The composition of the glassmay be, in weight per cent, SiO2, 71.38, Na2O + K2O 13.36, CaO 11.76, MgO 2., Na2SO40.75, Al2O3 0.15, Fe2O3 0.11, NaCl 0.06.

申请人：PPG IND. INC.

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