Method of varying the thickness of a glass sheet while on a molten metal bath

Claim 1

IN A PROCESS OF PRODUCING GLASS SHEET WHEREIN THE GLASS IS DEPOSITED UPON AND SUPPORTED ON A LIQUID HAVING A DENSITY GREATER THAN THAT OF THE GLASS AND THE GLASS WHEN MOLTEN AND ALLOWED TO FLOW FREELY ON SAID LIQUID TENDS TO NATURALLY ATTAIN AN EQUILIBRIUM THICKNESS, THE IMPROVEMENT WHICH COMPRISES, FLOATING A LAYER OF GLASS AT A TEMPERATURE AT WHICH IT FLOWS ON SAID LIQUID, FLOWING A PRESSURIZED GAS FROM A PLURALITY OF SPACED AND SEPARATE PRESSURE ZONES ONTO LATERALLY SPACED AREAS OF THE UPPER SURFACE OF THE GLASS BENEATH SAID ZONES LOCATED ABOVE EACH OF SAID AREAS AND WITHIN THE EDGES THEREOF, FLOWING THE GAS AT DIFFERENT PRESSURES FROM DIFFERENT ZONES ABOVE EACH SAID AREA, MAINTAINING THE PRESSURE OF THE ZONES ABOVE THE MOST CLOSELY ADJACENT PORTIONS OF SAID LATERALLY SPACED AREAS AT A FIRST PRESSURE WHICH IS SUBSTANTIALLY THE SAME AS THE PRESSURE BETWEEN SAID LATERALLY SPACED AREAS, MAINTAINING THE PRESSURE OF THE ZONES ABOVE THE MOST REMOTE PORTIONS OF SAID LATERALLY SPACED AREAS AT A SECOND PRESSURE WHICH IS SUBSTANTIALLY THE SAME AS THE PRESSURE BEYOND SAID LATERALLY SPACED AREAS AND ABOVE SAID SUPPORTING LIQUID, AND MAINTAINING A GRADIENT IN THE PRESSURES PROVIDED BY THE LATERALLY SPACED PRESSURE ZONES LOCATED BETWEEN EACH PAIR OF SAID PRESSUE ZONES PROVIDING SAID FIRST AND SECOND PRESSURE, WHEREBY TO SUBJECT LIQUID OUTSIDE AND IN CONTACT WITH THE GLASS TO A FLUID PRESSURE OF DIFFERENT MAGNITUDE THAN THAT OF SAID GAS BETWEEN SAID LATERALLY SPACED AREAS TO CONTROL THE THICKNESS OF THE GLASS WITHIN THE EDGES THEREOF SO AS TO BE DIFFERENT FROM SAID EQUILIBRIUM THICKNESS.