Glass manufacturing – Processes – Forming product or preform from molten glass
Patent
1992-04-13
1994-07-12
Jones, W. Gary
Glass manufacturing
Processes
Forming product or preform from molten glass
65 996, 651824, 65DIG13, 364473, C03B 1804, G06F 1546
Patent
active
053284950
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to a method and system for controlling the width of glass ribbon in a float bath, and more particularly to a method and system for controlling the width of ribbon in the float bath using fuzzy control.
2. Background Art
Transparent plate glass for building window panes or automotive windshields is usually manufactured by the so-called float process. As shown in FIG. 1, the float process for manufacturing plate glass consists of a smelting furnace 10 for melting raw materials to produce molten glass blank of consistent quality, a float bath 12 for forming molten glass into a plate shape, a Lehr(or annealing oven) 14 for annealing the formed plate glass, and a cutting section 16 for cutting the plate glass into cut-lengths and packaging them for shipment.
The float process is a plate-glass manufacturing method in which molten glass 11 is poured on a surface of molten metal (such as tin) 13 to obtain plate glass of a uniform thickness. This process was invented by an Englishman named Alastair Pilkinton in 1952.
Float glass manufactured by the float process is soda-lime glass consisting chiefly of 72% siliceous sand and 14% soda, for example. As the molten glass blank in the smelting furnace 10 is poured on the tin bath 12 while controlling the flow rate thereof, the molten glass spreads over the molten tin surface, and becomes a glass ribbon 15 having an equilibrium thickness of approximately 7 mm at a point where the surface tensions of glass, tin and atmosphere gas (N.sub.2 gas+H.sub.2 gas) at their respective interfaces, and the buoyancies and own weights of glass and tin are balanced. The ribbon of an equilibrium thickness is kept at a temperature suitable for the manufacture of plate glass (800.degree.-900.degree. C.), and slowly drawn into a plate of predetermined thickness and width, using care not to cause distortions.
Thus, the float process is divided into the following five steps:
1 Pouring molten glass from the furnace onto the bath
2 Reducing the molten glass ribbon to a uniform thickness on the molten tin
3 Controlling the thickness of the molten glass ribbon while maintaining the ribbon temperature at a plate-making temperature
4 Cooling the formed glass ribbon
5 Drawing the glass ribbon out of the tin bath
Float glass of thicknesses from 0.7 mm to 20.0 mm is manufactured by following the above steps.
As shown in FIG. 2 that is a cross-section of the float bath 12, FIG. 3 that is a plan view of the float bath, and FIG. 4 that is a cross-section of the tweel portion, a canal 18 is a narrow and shallow water passage through which the molten glass 11 at the central part of a smelting furnace 10 is poured onto the bath 12. On the canal 18, provided is a tweel 20. The tweel 20 is a damper, made of a refractory material, used for controlling the flow of the molten glass 11 from the furnace to the float bath 12, and sealing the atmosphere in the float bath 12. The tweel 20 can be raised and lowered by remote control from the float-bath control room. While monitoring the end of the glass ribbon at the entry of the float bath and at the hot end with left and right ITV cameras 22 and 24, the operator raises and lowers the tweel 20 through remote control so as to keep the width of the glass ribbon constant at the hot end.
The prior art requires the operator to raise and lower the tweel while monitoring the ribbon width at all times to control the ribbon width because of the lack of a system for controlling the raising and lowering of the tweel.
DISCLOSURE OF INVENTION
It is an object of this invention to automate the raising and lowering of the tweel through fuzzy control, that is, by replacing human visual and judgment functions with image processing and fuzzy control.
It is another object of this invention to provide a method of controlling the width of glass ribbon in the float bath, using fuzzy control.
It is still another object of this invention to provide a system for controlling the width of glass ribbon in the float bath, using f
REFERENCES:
patent: 4004900 (1977-01-01), Staahl, Jr. et al.
patent: 4030902 (1977-06-01), Nagae
patent: 4306898 (1981-12-01), Masuda et al.
patent: 4312656 (1982-01-01), Masuda et al.
patent: 4337076 (1982-06-01), Shaw, Jr.
Noguchi Junichi
Okafuji Masaharu
Otsuki Tomizo
Griffin Steven P.
Jones W. Gary
Nippon Sheet Glass Co. Ltd.
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