JP2000072457A - Forming of float sheet glass and its formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a defect arising from rolls by forcibly cooling both selvages of a glass strip near the inlet of a float bath or in the upstream area of a slow cooling kiln to form a cross-sectionally arch shape crowing in a central part in the axial direction of the glass strip to keep the glass strip contactless with the transporting rolls. SOLUTION: Selvages 4 of a glass strip 3 are forcibly cooled near the inlet of a float bath or in the inlet of a slow cooling kiln, by which the cross- sectionally arch shape crowing in the central part of the glass strip is formed. More specifically, blowing means 9 for a cooling medium to the selvages 4 of the glass strip 3 are disposed between the outlet of the float bath or the inlet of the slow cooling kiln, by which these potions are cooled. Air or gaseous nitrogen below ordinary temp. is used as the cooling medium. A central part 5 of the glass strip 3 in such a state does not came into contact with the transporting rolls and, therefore, the trouble by the contact with the rolls is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for forming a float glass sheet.

[0002]

2. Description of the Related Art In the manufacture of float glass sheets, defects such as roll flaws and adhesion of tin oxide deposited on the rolls often occur due to contact with a conveying roll in a state where the glass strip has not yet solidified.

As a method for preventing this, there is a method in which sulfur dioxide gas is brought into contact with the glass surface to form a protective coating of sodium sulfate on the glass surface. In the near future, this method will not be adopted in the near future.

Japanese Patent Application Laid-Open No. 53-75212 discloses that, when a glass strip is drawn out of a float bath and supported by a gas cushion from below, the supply and discharge of gas are adjusted to reduce the glass strip. It is disclosed that the cross section has an arch shape and the defect is eliminated. However, in forming the gas cushion, the equipment scale becomes large and gas adjustment is not easy.

An object of the present invention is to provide a method and an apparatus for forming a float glass sheet which can solve the above-mentioned problems and can suppress the occurrence of defects caused by rolls by simple means.

[0006]

According to the present invention, the center of the glass strip in the width direction is formed by forcibly cooling both ears of the glass strip at the float bath outlet or in the upstream area of the lehr in the manufacture of the float glass sheet. This is a method for forming a float glass sheet that forms a convex, cross-section arched shape and is not in contact with a transport roll.

Further, according to the present invention, there is provided a means for blowing a cooling medium to both ears of a glass strip at an appropriate position in a float bath outlet or an upstream area of an annealing furnace, or at both ears of a glass strip. Provided is an apparatus for forming a float glass sheet used in the method for forming a float glass sheet, wherein a pipe for guiding a cooling medium is brought close to the pipe.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an example of a moving state of a glass strip from a float bath to a slow cooling kiln in sheet glass production, and an example of cooling means for both ears of a glass strip (an example of spraying a cooling medium to both ears of a glass strip). Schematic partial longitudinal sectional view,
2A is a schematic partial perspective view showing a cooling state of the both ears of the glass strip according to FIG. 1, and FIG. 2B is an enlarged partial perspective view of FIG. 2A.

In the manufacture of a float glass sheet, a glass raw material mixture is charged into a glass melting furnace (not shown), melted, homogenized, defoamed and clarified, and then melted in a float bath 1. It is cast on a tin bath 2 and the float bath 1 (the atmosphere in the bath is a nitrogen gas containing no oxygen, a hydrogen gas, or a mixed gas thereof so as not to oxidize the metal tin is used for forming a float glass sheet. In conventional technical means), both sides in the width direction of the glass are further pulled to both sides from the upper surface side of the cast glass by a well-known top roll or the like (not shown), and formed into a desired glass thickness (plate making). ), Adjusted.

[0010] The glass strip 3 thus formed has both sides in the width direction including the top roll pulling traces, that is, the ears 4 coexisting with the central part 5 capable of sampling, and the float bath as it is. 1 and then sent to the slow cooling kiln 6 where it is gradually cooled. The glass strip 3 transferred from the annealing furnace 6 is sampled after cutting and removing the both ears in a sampling step (not shown).

A glass strip 3 drawn from a float bath 1
Surface exceeds the strain point (about 520 ° C for ordinary soda-lime-silica glass, and the coefficient of thermal expansion is about 90 × ^10-7 / ° C for soda-lime-silica glass). The inside is in a heat-softened state with a higher temperature. Until the glass strip 3 is sufficiently solidified in the annealing furnace 6, the lift-out roll 7 when it is drawn from the float bath 1 and the transfer in the annealing furnace 6 When the lower surface of the central portion 5 of the glass strip comes into contact with the roll 8, the roll marks, the roll scratches, and the transfer and transfer of tin oxide deposited on the roll,
Defects often detract from commercial value.

As described above, there is also a method in which sulfur dioxide gas is brought into contact with the glass surface to form a mirabilite film, that is, a protective coating on the glass surface. However, this method tends to be avoided due to environmental problems.

In the present invention, the central portion 5 in the width direction of the glass strip 3 is protruded by forcibly cooling the both ears 4 of the glass strip 3 near the outlet of the float bath 1 or the inlet of the lehr 6. , A cross-section arch shape is formed.

More specifically, as one embodiment, at an appropriate place between the outlet of the float bath 1 and the inlet of the lehr 6, preferably near the outlet of the float bath 1, the both ends 4 of the glass strip 3 are connected. A cooling medium blowing means 9 is provided to cool the part.
Air or nitrogen gas having a temperature of 30 ° C. or lower, for example, nitrogen gas which does not react with the glass and does not deteriorate the glass, is blown through a blowing slit or a blowing nozzle 9 as shown in the drawing. Wing.

[0015] One embodiment conditions and results are shown below. Float glass band width: 3.3 m Float glass transfer speed: 11 m / min Nitrogen gas (approximately 30 ° C.) spray amount: 5 L / min on one side (10 L / min on both sides)
Minute) Width of the center of the float glass in the width direction: 5 cm (Fig. 2A)
(Indicated by z)

As another example, while cooling from the vicinity of the outlet of the float bath 1 to the entrance of the annealing furnace 6, the cooling belt 20 is placed immediately below both ears 4 of the glass strip (at a distance of 10 mm or less from the ears). When a pipe through which water of about ° C. was passed was placed close to the pipe, an upwardly convex arch shape was formed in the center portion 5 of the glass band as described above.

The effect of the local (ear) cooling is not fully understood, but as shown in FIG. 2B, the ear 4 of the glass band shrinks as shown by the arrow → ← x due to cooling, while the center of the glass band is contracted. 5 is maintained at a higher temperature and is in a state of being relaxed in an expanded state as shown by an arrow ← → y, so that the center portion 5 of the glass strip can be bent upward and downward, but the downward bending is performed by a transfer roll. Regulated and
It is presumed that in the downstream region of the glass strip, as a result of uniform cooling, solidification, and flattening of the entire glass strip, the glass strip central portion 5 of the part forms a convex, cross-sectional arch shape.

In the glass strip 3 having such a configuration, the central portion 5 does not come into contact with the rolls 7 and 8, so that the above-mentioned adverse effects caused by contact with the rolls 7 and 8 can be eliminated. In addition, in a means for bringing a pipe for guiding a cooling medium close to both ears of the glass strip and cooling through the pipe, in addition to the water-cooled pipe, the pipe may be a wind-cooled pipe, or another pipe for easily vaporizing liquid. There is.

The cross-section arch-shaped structure of the glass band formed by cooling the ear portion is characterized in that when the entire surface of the glass band in the width direction is gradually cooled through the downstream area of the slow cooling kiln, the forced cooling is performed. By eliminating the temperature difference between the ear part, the center part of the glass band, and the inside of the glass band, the glass band itself is flattened, and the flatness of the glass plate is not impaired at the time of sampling, and as a flat glass Quality can be maintained.

[0020]

According to the present invention, there is an effect that in the production of a float plate glass, the occurrence of defects caused by rolls can be suppressed by an easy means.

[Brief description of the drawings]

FIG. 1 shows a moving state of a glass strip from a float bath to a slow cooling kiln in sheet glass production, and an example of cooling means for both ears of a glass strip (an example of spraying a cooling medium to both ears of a glass strip). It is a general | schematic partial longitudinal cross-sectional view shown.

FIG. 2A is a schematic partial perspective view showing a cooling state of both ears of a glass strip according to FIG. 1, and FIG. 2B is an enlarged partial perspective view of FIG. 2A.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Float bath 2 Molten tin bath 3 Glass band 4 Edge of glass band 5 Central part of glass band 6 Slow-cooling kiln 7 Lift-out roll 8 Transfer roll 9 Blowing means (spray nozzle)

Claims (3)

[Claims] 1. An arc-shaped cross section in which a central portion in a width direction of a glass band is convex by forcibly cooling both ears of a glass band at a float bath outlet or an upstream region of a lehr in a float glass sheet production. And forming the float glass out of contact with a transport roll. 2. A float glass sheet according to claim 1, wherein blow means for blowing a cooling medium to both ears of the glass strip is provided at an appropriate position from the float bath outlet to the upstream area of the lehr. For forming a float glass sheet used in the method for forming a glass sheet. 3. The float glass sheet according to claim 1, wherein a pipe for guiding a cooling medium is brought close to both ears of the glass strip at an appropriate position from the float bath outlet to the upstream area of the lehr. An apparatus for forming a float glass sheet used in the method.