US3342574A - Manufacture of flat glass on improved molten metal bath - Google Patents

Manufacture of flat glass on improved molten metal bath Download PDF

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Publication number
US3342574A
US3342574A US367115A US36711564A US3342574A US 3342574 A US3342574 A US 3342574A US 367115 A US367115 A US 367115A US 36711564 A US36711564 A US 36711564A US 3342574 A US3342574 A US 3342574A
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US
United States
Prior art keywords
bath
glass
tin
molten
alloy
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US367115A
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English (en)
Inventor
Jewell Ronald Colgan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pilkington Group Ltd
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Pilkington Brothers Ltd
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Filing date
Publication date
Application filed by Pilkington Brothers Ltd filed Critical Pilkington Brothers Ltd
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B18/00—Shaping glass in contact with the surface of a liquid
    • C03B18/02—Forming sheets
    • C03B18/18—Controlling or regulating the temperature of the float bath; Composition or purification of the float bath

Definitions

  • the molten bath is constituted in its preferred form, of tin alone or of an alloy of tin and another metal in which alloy tin predominates, and in order to prevent contaminants being present at the interface between the glass and the bath a plenum of protective atmosphere is maintained in the headspace over the bath to exclude ambient atmosphere from the headspace.
  • flat glass in ribbon form is advanced over a molten alloy
  • the present invention comprises advancing the glass over a molten alloy of tin and a noble metal in the manufacture of flat glass in ribbon form which noble metal forms at the operating temperature an oxide which is much less thermodynamically stable than an oxide of tin.
  • noble metal is meant one of the metals silver, gold, platinum, palladium or rhodium, or an alloy of two or more of the said noble metals, e.g. a silver/gold alloy.
  • the present invention also comprises advancing the glass in ribbon form over a molten alloy of tin and a noble metal, which alloy includes a proportion of a noble metal, which alloy includes a proportion of a noble metal such that the alloy has a melting point below 700 C and from this aspect the present invention comprises 'a inbath of molten tin in a proportion to form a tin alloy having a melting point below 700 C., which noble metal forms at the operating temperature an oxide which is less thermodynamically stable than an oxide of tin.
  • silver is incorporated in the molten alloy, the presence of which silver modifies the entry of contaminants into the glass at the interface between the glass and the molten metal, thereby minimising any possibility of harmful contaminants entering the glass; while the tin component ensures the desired low melting temperature for the bath as well as the other desirable characteristics for the bath hereinbefore defined.
  • the molten alloy can be suitably constituted by using 30% of silver.
  • the molten alloy may contain silver and tin in equal proportions as even in that case there is sufficient tin to achieve a sufficiently low melting temperature (in this case the melting point of the bath is about 500 C.) for the production of flat glass in continuous ribbon form and the reduction of the tin content to 50% materially assists in minimising the possibility of harmful contaminants entering the glass.
  • FIGURE 1 is a sectional elevation of rolling means for converting molten glass into a ribbon of glass for delivery on to a bath of molten alloy contained in a tank structure, and
  • FIGURE 2 is a sectional elevation showing a modified method of delivering glass to the bath of molten lalloy.
  • FIGURE 1 there is illustrated a forehearth of a continuous glass melting furnace, indicated at 1, a regulating tweel at 2, and a spout at 3.
  • the spout comprises a lip 4 and side jambs 5, of which only one is illustrated.
  • the side -jam bs 5 and lip 4 together form a spout of generally rectangular cross-section.
  • a cover may be secured over the spout.
  • a pair of water cooled casting rolls indicated at 6 and 7. These rolls are mounted on frames 8 in the usual manner and are driven by power means, not shown.
  • a gate 9 is ad justably suspended in known manner, by means not shown, in a vertical plane in contig-uity with the upper casting roll 6. The gate 9 shields the top roll 6 from heat radiated by molten glass 10 flowing from the forehearth over the lip 4 to the pass between the rolls 6 and 7.
  • the upper casting roll 6 is disposed in advance of the lower casting roll 7 so that the molten glass flows from the lip 4 on to an upper part of the roll 7 presenting to the glass a downwardly and forwardly directed arcuate casting bed moving in the same sense as the direction of flow from the spout.
  • the molten glass on leaving the spout and arriving on this casting bed is constrained to flow forwardly, thereby preventing backward flow of the molten glass leaving the spout 4.
  • the conventional ribbon forming means is disposed over the floor 11 of a tank structure also including integral side walls :12 and integral end walls 13 and 14 respectively situated at the inlet and outlet ends of the tank structure.
  • the tank structure contains a bath 15 of a molten alloy of tin and a noble metal, preferably silver, for example a bath of molten tin containing 10% of silver.
  • the bath has all the characteristics hereinbefore defined of the bath described in U.S.A. Patents Nos. 2,911,759 and 3,083,551.
  • the surface level of the bath of molten alloy is indicated at 16.
  • the tank structure supports a roof structure including a roof '17 and a vertically adjustable end wall at each end of the roof.
  • the adjustable end wall near the casting rolls is indicated at 18, and the adjustable end wall at the outlet end of the tank structure is indicated at 19.
  • the roof structure provides a tunnel over the "bath 15 and defines a headspace 20 thereover.
  • the adjustable end wall 18 of the roof structure forms part of an enclosure for the casting rolls 6 and 7.
  • This enclosure has a ceiling 21 and side walls 22, which side walls 'are carried by the side walls 12 of the tank structure.
  • the ceiling 21 extends between the regulating gate 9 and the end wall '18.
  • protecting atmosphere such, for example, as disclosed in said Patents 2,911,758 and 3,083,551 is maintained at a plenum in the headspace 20 over the bath 15, the protecting atmosphere being supplied through a series of ducts 23 connected by branches 24 to headers 25. Further, the passage of protecting atmosphere under the end wall 18 into the enclosure housing the rolls '6 and '7 ensures that the rolls operate in that atmosphere, thereby protecting the rolls from corrosion on their surfaces. The existence of a plenum in the headspace 20 and the enclosure for the casting rolls 6 and 7 prevents the ingress of ambient atmosphere.
  • the temperature of the molten bath '15 is regulated from the inlet end to the discharge end by providing thermal regulators 26 immersed in the bath. Radiant heaters 27 are provided in the headspace 20 to assist the temperature regulation.
  • the bath may be maintained at such a temperature, e.g. 650 C., that it is not hot enough to melt the surfaces of the rolled ribbon of glass 28 as the ribbon glides along the bath; or the temperature of the bath can be regulated so that the ribbon of glass 28 is superficially melted as it glides along the bath and is then cooled before it is discharged from the bath to a state in which it can be taken off the bath unharmed by mechanical means, the ultimate ribbon of glass having a lustre of fire finish quality.
  • conveying rollers 29 which are disposed somewhat above the top of the end wall 14 of the tank structure.
  • the ribbon of g ass 28 is taken-up off the bath by the rollers 29 and conveyed to a conventional tunnel lehr, not shown.
  • Impurities for example oxygen and/or sulphur may be present in the protective atmosphere over the bath of molten alloy or may migrate into the bath from the glass delivered to the bath. This may result in the presence of contaminants in the bath.
  • a noble metal in the bath for example silver which may be present in a proportion which is as low as 1%, modifies the entry of contaminants into the glass as the ribbon glides over the molten alloy bath 15, thus minimising the entry of harmful contaminants into the glass.
  • FIGURE 2 A modified process of producing flat glass is shown in FIGURE 2.
  • Glass in molten form is supplied to the bath from the spout 4, of the forehearth 1, and the gate 9 affords a constant regulation to control the flow of molten glass 60 from the spout lip 4; thus the flow is control-led by the regulating tweel 2 and the gate 9.
  • the spout lip 4 is vertically spaced from the surface of the 4- bath so that the molten glass has a free fall of a few inches to the bath, which distance is such as to ensure a heel 31 being formed behind the glass flowing to the bath, which heel extends rearwardly under the spout lip 4 to the end wall 13.
  • the temperature at the inlet end of the bath is maintained at about 1000 C. or slightly higher over a sufficient length of the 'bath to ensure that a buoy-ant layer of molten glass 32 is established on the bath from which layer is developed a buoyant body of molten glass 33 by permitting the buoyant layer to how laterally unhindered to the limit of its free flow, the width of the tank structure being somewhat greater than the width of the buoyant body 3 3 of molten glass at the surface level 16 of the molten alloy bath.
  • the presence of the noble metal in the bath 15 ensures that the entry of contaminants into the glass is minimised as the buoyant body of molten glass 33 is developed and is advanced in ribbon form along the bath, which ribbon is cooled on the bath until it is sufficiently stiffened to be taken off the 'bath unharmed by the rollers 29, the outlet end of the tank structure being identical to the outlet end of the tank structure illustrated in FIGURE 1.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Glass Compositions (AREA)
  • Catalysts (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
US367115A 1963-05-16 1964-05-13 Manufacture of flat glass on improved molten metal bath Expired - Lifetime US3342574A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB19585/63A GB1020588A (en) 1963-05-16 1963-05-16 Improvements in or relating to the manufacture of flat glass in ribbon form

Publications (1)

Publication Number Publication Date
US3342574A true US3342574A (en) 1967-09-19

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
US367115A Expired - Lifetime US3342574A (en) 1963-05-16 1964-05-13 Manufacture of flat glass on improved molten metal bath

Country Status (8)

Country Link
US (1) US3342574A (de)
BE (1) BE648008A (de)
CH (1) CH420504A (de)
DE (1) DE1471968A1 (de)
ES (1) ES299901A1 (de)
GB (1) GB1020588A (de)
LU (1) LU46098A1 (de)
NL (1) NL6405433A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3445217A (en) * 1965-11-03 1969-05-20 Pilkington Brothers Ltd Composite tweel with internal suspension system
US3468653A (en) * 1965-03-22 1969-09-23 Pilkington Brothers Ltd Lateral confinement and flow-halting apparatus for manufacture of flat glass
US6065309A (en) * 1997-09-20 2000-05-23 Wisconsin Alumni Research Foundation Float processing of high-temperature complex silicate glasses and float baths used for same
WO2007019840A1 (de) * 2005-08-19 2007-02-22 Schott Ag Verfahren zur vermeidung von oberflächendefekten bei gefloatetem flachglas sowie das flachglas und seine verwendung
US11390552B1 (en) * 2021-11-12 2022-07-19 James W. Masten, Jr. Thermophysical float glass process

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3083551A (en) * 1957-05-03 1963-04-02 Pilkington Brothers Ltd Manufacture of flat glass
US3233995A (en) * 1961-06-23 1966-02-08 Glaverbel Process and apparatus for producion of continuous fire-polished glass sheet

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3083551A (en) * 1957-05-03 1963-04-02 Pilkington Brothers Ltd Manufacture of flat glass
US3233995A (en) * 1961-06-23 1966-02-08 Glaverbel Process and apparatus for producion of continuous fire-polished glass sheet

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3468653A (en) * 1965-03-22 1969-09-23 Pilkington Brothers Ltd Lateral confinement and flow-halting apparatus for manufacture of flat glass
US3445217A (en) * 1965-11-03 1969-05-20 Pilkington Brothers Ltd Composite tweel with internal suspension system
US6065309A (en) * 1997-09-20 2000-05-23 Wisconsin Alumni Research Foundation Float processing of high-temperature complex silicate glasses and float baths used for same
WO2007019840A1 (de) * 2005-08-19 2007-02-22 Schott Ag Verfahren zur vermeidung von oberflächendefekten bei gefloatetem flachglas sowie das flachglas und seine verwendung
US11390552B1 (en) * 2021-11-12 2022-07-19 James W. Masten, Jr. Thermophysical float glass process

Also Published As

Publication number Publication date
ES299901A1 (es) 1964-12-01
NL6405433A (de) 1964-11-17
LU46098A1 (de) 1965-11-16
GB1020588A (en) 1966-02-23
DE1471968B2 (de) 1970-06-18
BE648008A (de) 1964-11-16
DE1471968A1 (de) 1969-03-27
CH420504A (fr) 1966-09-15

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