WO2011106605A2

WO2011106605A2 - Apparatus for making a glass article and methods

Info

Publication number: WO2011106605A2
Application number: PCT/US2011/026184
Authority: WO
Inventors: William Gurney Dorfeld; Randy Rhoads
Original assignee: Corning Incorporated
Priority date: 2010-02-25
Filing date: 2011-02-25
Publication date: 2011-09-01
Also published as: JP2013521205A; KR20130024889A; KR101848101B1; TWI494283B; CN102770378A; TW201134773A; JP5885674B2; CN102770378B; WO2011106605A3

Abstract

Apparatus are provided for making a glass article. The apparatus includes a pre-fining chamber with a first stirring device for stirring molten glass in the pre-fining chamber. The apparatus further includes a fining chamber configured to remove a majority of the gas bubbles from the molten glass. The apparatus also includes a post-fining chamber with a second stirring device for stirring molten glass in the post-fining chamber. Methods are also provided for making a glass article. The methods include the steps of stirring molten glass in a pre-fining chamber, removing a majority of the gas bubbles from the molten glass in a fining chamber, and stirring the molten glass in the post-fining chamber.

Description

APPARATUS FOR MAKING A GLASS ARTICLE AND METHODS

[0001] This application claims the benefit of priority to US Patent Application No. 61/308067 filed on February 25, 2010.

TECHNICAL FIELD

[0002] The present invention relates generally to apparatus for making a glass article and methods, and more particularly, to apparatus and methods that stir the molten glass in a pre-fining chamber and a post-fining chamber.

BACKGROUND

[0003] Glass manufacturing systems are commonly used to form various glass articles such as liquid crystal display (LCD) sheet glass. For example, it is known to flow molten glass into an isopipe wherein a glass ribbon is formed by a fusion down-draw process. The glass ribbon may then be subsequently divided to provide LCD sheet glass. SUMMARY

[0004] In one example embodiment, a method of making a glass article is provided. The method comprises the step of melting batch material in a glass melter to produce molten glass comprising tin oxide. The method further includes the steps of passing the molten glass from the glass melter to a pre-fining chamber and stirring the molten glass in the pre-fining chamber. The method still further includes the steps of passing the molten glass from the pre-fining chamber to a fining chamber and removing a majority of the gas bubbles from the molten glass in the fining chamber. The method further includes the step of passing the molten glass from the fining chamber to a post- fining chamber, wherein a temperature of the molten glass in the post-fining chamber is lower than a temperature of the molten glass in the pre-fining chamber. The method further includes the steps of stirring the molten glass in the post-fining chamber and passing the quantity of molten glass from the post-fining chamber to a forming vessel to form the glass article.

[0005] In another example embodiment, an apparatus for making a glass article is provided. The apparatus includes a glass melter configured to melt a batch material into a molten glass and a pre-fining chamber configured to receive molten glass from the glass melter. The pre-fining chamber includes a first stirring device for stirring molten glass in the pre-fining chamber. The apparatus further includes a fining chamber configured to receive molten glass from the pre-fining chamber and remove a majority of the gas bubbles from the molten glass. The apparatus also includes a post- fining chamber configured to receive molten glass from the fining chamber. The post-fining chamber includes a second stirring device for stirring molten glass in the post-fining chamber, wherein the second mixing device is configured to stir the molten glass with less stir shearing than the first stirring device. The apparatus still further includes a forming vessel configured to receive molten glass from the post-fining chamber and form the glass article.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] These and other aspects are better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0007] FIG. 1 is a schematic view of an apparatus for making a glass sheet;

[0008] FIG. 2 is an enlarged view of portions of the apparatus of FIG. 1;

[0009] FIG. 3 is a section view along line 3-3 of FIG. 2; and

[0010] FIG. 4 is a section view along line 4-4 of FIG. 2.

DETAILED DESCRIPTION

[0011] Examples will now be described more fully hereinafter with reference to the accompanying drawings in which example embodiments are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0012] FIG. 1 is a schematic illustration of an apparatus 101 configured to make a glass article. In one example, the glass article can comprise a glass art piece, a glass container, a glass rod, a glass tube or other glass articles. The apparatus 101 may also be used to create glass articles that are desirably substantially free of gas bubbles within the glass article. For example, glass articles can further include components of an optical device, such as one or more glass lenses of the optical device. In further example, the glass article can comprise a glass sheet, such as a glass sheet for an LCD display.

[0013] As further illustrated in FIG. 1, the apparatus 101 includes a glass melter

103 configured to melt a batch material 105 from a storage bin 107. The batch material can be introduced by a batch delivery device 109 through an inlet port of the glass melter 103 along directional arrow 111. Inside the glass melter 103, the batch material 105 is melted into a molten glass 113. The molten glass 113 may have various compositions depending on the desired glass article characteristic and process considerations. For instance, the molten glass 113 may include volatile components provided to enhance fining of gas bubbles from the molten glass to produce a glass article substantially free of gas bubbles. As illustrated schematically, the molten glass 113 can include volatile components such as tin oxide (Sn0₂) and/or boron oxide (B₂0₃).

[0014] The apparatus 101 further includes a pre-fining chamber 115 configured to receive the molten glass 113 from the glass melter 103. As schematically shown in

FIGS. 1 and 2, the pre-fining chamber 115 includes a first stirring device 117 for stirring the molten glass 113 in the pre-fining chamber 115. The first stirring device 117 may be configured to rotate about a vertical axis along directional arrow 119 although it is contemplated that the stirring device may be rotated about an angled axis, horizontal axis or the like. In addition or alternatively, the stirring device may orbit about an axis, such as a central axis, of the pre-fining chamber 115. In the illustrated example, the first stirring device 117 includes a vertical shaft 121 extending along a central axis of the pre- fining chamber 115. A first stir-blade configuration 123 including a first set of blades 125 that may be integrally attached to the vertical shaft 121. A first motor 127 may be operably connected to rotate the vertical shaft 121 along directional arrow 119 to cause the first stir-blade configuration 123 to stir the molten glass 113 within the pre-fining chamber 115.

[0015] As shown in FIG. 2, the pre-fining chamber 115 includes an inlet 129 for receiving the molten glass from the glass melter 103. As shown in FIG. 3, the example inlet 129 includes an elevational height 131. The inlet 129 may have a circular periphery wherein the elevational height 131 comprises the diameter of the inlet 129. Although not shown, the inlet 129 may have other shapes such as polygonal (e.g., triangular, rectangular, etc.), curvilinear or other configurations. As further shown in FIGS. 2 and 3 the pre-fining chamber 115 further includes an outlet 133 that may have a periphery geometrically similar to the periphery of the inlet 129 although different shapes may be provided in further examples. As shown in FIG. 2, the inlet 129 of the pre-fining chamber 115 may be positioned at a lower elevation than the outlet 133, thereby allowing cross-flow of the molten glass 113 within the pre-fining chamber 115. Providing a cross- flow of the molten glass 113 can promote interaction with the first stir-blade

configuration 123 to mix the molten glass 113 prior to passing through the outlet 133. [0016] The apparatus 101 further includes a fining chamber 135 configured to receive the molten glass 113 from the pre-fining chamber 115 and remove a majority of the gas bubbles 137 from the molten glass 113. As shown, the fining chamber 135 may comprise an elongated horizontal tube although other chamber configurations may be provided in further examples. As further illustrated, the fining chamber 135 may optionally be vented to the atmosphere. Thus, example embodiments may provide a fining chamber wherein essentially no vacuum is imposed on the molten glass 113 within the fining chamber 135. As used herein, essentially no vacuum is intended to mean that the atmosphere in the fining chamber 135 has a pressure of at least 0.8 atmospheres. Thus, essentially no vacuum can include embodiments where light vacuum is applied while pressures below 0.8 atmospheres are avoided.

[0017] The apparatus 101 further includes a post-fining chamber 139 configured to receive the molten glass 113 from the fining chamber 135. As schematically shown in FIGS. 1 and 2, the post-fining chamber 139 includes a second stirring device 141 for stirring the molten glass 113 in the post-fining chamber 139. The second stirring device 141 may be configured to rotate about a vertical axis along directional arrow 143

although it is contemplated that the stirring device may be rotated about an angled axis, horizontal axis or the like. In addition or alternatively, the stirring device may orbit about an axis, such as a central axis, of the post-fining chamber 139. In the illustrated example, the second stirring device 141 includes a vertical shaft 145 extending along a central axis of the post-fining chamber 139.

[0018] A second stir-blade configuration 147 including a second set of blades 149 that may be integrally attached to the vertical shaft 145. The first stirring device 117 may be configured to stir the molten glass 113 with less stir shearing than the second stirring device 141. In one example, the second stir blade configuration includes a larger molten glass shearing surface area than a molten glass shearing surface area of the first stir-blade configuration. Indeed, as apparent in FIG. 2, the second set of blades 149 of the second stir-blade configuration 147 includes a greater number of blades than the first set of blades 125 of the first stir-blade configuration 123. As such, second stir-blade configuration 147 includes a larger molten glass shearing surface area than a molten glass shearing surface area of the first stir-blade configuration 123.

[0019] A second motor 151 may be operably connected to rotate the vertical shaft

145 along directional arrow 143 to cause the second stir-blade configuration 147 to stir the molten glass 113 within the post- fining chamber 139. As shown, the second motor 151 may be larger and/or configured to deliver more torque than the first motor 127. As such, the first stirring device 117 may be configured to stir the molten glass 113 with less stir shearing than the second stirring device 141 even in examples where the first stir- blade configuration is identical or similar to the second stir-blade configuration.

[0020] As shown in FIG. 2, the post-fining chamber 139 includes an inlet 153 for receiving the molten glass from the fining chamber 135 and an outlet 155 for passing the molten glass 113 to a delivery vessel 157 (e.g., a bowl). As shown in FIG. 2, the inlet 153 of the post-fining chamber 139 may be positioned at a higher elevation than the outlet 155, thereby allowing cross-flow of the molten glass 113 within the post-fining chamber 139. Cross-flow of the molten glass 113 promotes interaction with the second stir-blade configuration 147 to mix the molten glass 113 prior to passing through the outlet 155.

[0021] The apparatus 101 further includes a forming vessel configured to receive the molten glass from the post-fining chamber and form the glass article. The forming vessel can include fusion down-draw, slot draw, float, pressing, molding, rolling, injection molding and the like. As shown in FIG. 1, for example, the forming vessel can comprise an isopipe 159 configured to fusion down-draw the glass article, such as the illustrated glass ribbon 161 from the molten glass 113 by a fusion-draw technique.

[0022] The glass me Iter 103 is typically made from a refractory material, such as refractory (e.g., ceramic) brick. The apparatus 110 may further include components that are typically made from platinum or platinum-containing metals such as platinum- rhodium, platinum-iridium and combinations therefore, but which may also comprise such refractory metals as molybdenum, palladium, rhenium, tantalum, titanium, tungsten, ruthenium, osmium, zirconium, and alloys thereof and/or zirconium dioxide. The platinum- containing components can include one or more of the pre-fining chamber 115, the fining chamber 135, the post-fining chamber 139, the delivery vessel 157, a downcomer 163 and an inlet 165 to the forming vessel. The platinum-containing components can also include one or more of the connecting tubes connecting the various vessels to one another.

[0023] Referring to FIG. 1, methods of making a glass article comprises the step of melting batch material 105 in the glass melter to produce a molten glass 113 with tin oxide. In one example, the molten glass may also include boron oxide. Once melted, the molten glass 113 passes from the glass melter 103 and through the inlet 129 of the pre- fining chamber 115 and then stirred within the pre-fining chamber 115 by the first motor 127. As schematically illustrated in FIG. 3, the molten glass 113 may be introduced into the pre-fining chamber 115 as a molten glass stream 113 wherein at least the upper 20% (represented by reference number 167) of the elevational height of the molten glass stream entering the pre-fining chamber is mixed throughout at least 75% of an elevational height 169 of the molten glass 113 within the pre-fining chamber 115. Providing sufficient mixing of the upper portion of the elevational height of the molten glass stream can help homogenize the glass melt by distributing the tin oxide, boron oxide, and or other fining agents throughout molten glass passing out through the outlet 133, thereby increasing the effectiveness of gas bubble removal in the fining chamber 135. As schematically shown in FIG. 3 by the "+" markers 171, the upper elevational 20% (reference number 167) may have less than the average distribution of tin oxide and/or boron oxide. However, after stirring with the first stirring device 117, the markers 171 are more desirably dispersed throughout the exiting glass melt stream passing through the outlet 133 to the fining chamber 135. Forming a more homogeneous melt in the pre- fining chamber has the further advantage of minimizing regions of high water content in the molten glass stream. Localized high water content in the region shown in FIG. 3 with "+" markers 171 can be created, for example, when the glass melter 103 utilizes gas- oxygen burners to heat the molten glass surface. Contact of the molten glass with the water-rich gas-oxygen combustion atmosphere will enrich the surface region in water. If water-rich regions of the molten glass stream subsequently contact platinum-containing vessel wall bubbles may be produced when the dissolved water breaks down to hydrogen, which permeates the walls leaving behind oxygen, which may form bubbles and subsequent defects in the final glass product if hydrogen permeation is not properly controlled. After stirring with the first stirring device 117, the water content is more favorably shifted toward a uniform concentration. The stirring procedure within the pre- fining chamber 115 may involve relatively low stir shearing of the molten glass to provide adequate distribution of the fining agents. As such, energy may be saved and costly stirring components may be simplified or reduced.

[0024] As shown in FIG. 2, once the molten glass stream then enters the fining chamber wherein the gas bubbles 137 may freely rise to the surface 173 of the glass melt within the fining chamber 135 to be released to the atmosphere 175 within the fining chamber. A pressure equalization valve 177 may optionally be provided to ensure that essentially no vacuum is imposed to facilitate removal of the gas bubbles from the molten glass. As essentially no vacuum is imposed, excess volatilization of tin oxide and/or boron oxide inside the fining chamber 135 can be avoided. After passing through the fining chamber 135, the molten glass 113 is essentially free of any gas bubbles.

However, cord forming parts 179 may be formed that represent nonhomogeneous portions of the molten glass.

[0025] The molten glass 113 then enters the post-fining chamber 139 wherein the molten glass is stirred with the second stirring device 141. Once the glass melt passes to the forming vessel (e.g., isopipe 159), the molten glass comprises a substantially homogeneous composition essentially free of cord-forming parts.

[0026] As indicated by temperature gauges 181, 183 a temperature of the molten glass in the post-fining chamber is lower than a temperature of the molten glass in the pre- fining chamber. As such the molten glass 113 may include a viscosity that is lower in the pre-fming chamber than the post-fining chamber. In order to sufficiently stir the molten glass, a larger motor 151 (when compared to motor 127) may be used and the stir- shearing within the post-fining chamber may be higher than the stir-shearing in the pre- fming chamber. Moreover, the molten glass may be mixed more in the post-fining chamber than the pre-fming chamber in order to sufficiently homogenize the glass melt before entering the forming vessel.

[0027] The glass melt may then enter the forming vessel to form the glass article.

For example, as shown, the forming vessel comprises an isopipe 159 and the glass article comprises a glass sheet formed from a glass ribbon 161 by a fusion down-draw process.

[0028] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the claimed invention.

Claims

1. A method of making a glass article comprising the steps of:

(I) melting batch material in a glass melter to produce molten glass comprising tin oxide;

(II) passing the molten glass from the glass melter to a pre-fining chamber;

(III) stirring the molten glass in the pre-fining chamber;

(IV) passing the molten glass from the pre-fining chamber to a fining chamber;

(V) removing a majority of the gas bubbles from the molten glass in the fining chamber;

(VI) passing the molten glass from the fining chamber to a post-fining chamber, wherein a temperature of the molten glass in the post-fining chamber is lower than a temperature of the molten glass in the pre-fining chamber;

(VII) stirring the molten glass in the post-fining chamber; and

(VIII) passing the quantity of molten glass from the post-fining chamber to a forming vessel to form the glass article.

2. The method according to claim 1, wherein the forming vessel comprises an isopipe and the glass article comprises a glass sheet formed by a fusion down-draw process.

3. The method according to any one of the preceding claims, wherein the molten glass comprises boron oxide.

4. The method according to any one of the preceding claims, wherein the molten glass includes a viscosity that is lower in the pre-fining chamber than the post-fining chamber.

5. The method according to any one of the preceding claims, wherein the molten glass in the pre-fining chamber is subjected to less stir shearing than the molten glass in the post- fining chamber.

6. The method according to any one of the preceding claims, wherein the molten glass is mixed in both the pre-fining chamber during step (III) and the post-fining chamber during step (VII), wherein the molten glass is mixed more in the post-fining chamber during step (VII) than the molten glass is mixed in the pre-fining chamber during step (III).

7. The method according to any one of the preceding claims, wherein during step (II), the molten glass is introduced into the pre-fining chamber as a molten glass isixeam inciuuing an eievauuiiai neigiii, wiiereiii ai leajsi an upper zu7o υι me

elevational height of the molten glass stream entering the pre-fining chamber is mixed throughout at least 75% of an elevational height of the molten glass within the pre- fining chamber during step (III).

8. The method according to any one of the preceding claims, where at the end of step (VII), the molten glass has a substantially homogeneous composition essentially free of cord-forming parts.

9. The method according to any one of the preceding claims, wherein during step (V), essentially no vacuum is imposed to facilitate removal of the gas bubbles from the molten glass.

10. An apparatus for making a glass article comprising:

(A) a glass melter configured to melt a batch material into a molten glass;

(B) a pre-fining chamber configured to receive molten glass from the glass melter, the pre-fining chamber including a first stirring device for stirring molten glass in the pre- fining chamber;

(C) a fining chamber configured to receive molten glass from the pre-fining chamber and remove a majority of the gas bubbles from the molten glass;

(D) a post-fining chamber configured to receive molten glass from the fining chamber, the post-fining chamber including a second stirring device for stirring molten glass in the post-fining chamber, wherein the second mixing device is configured to stir the molten glass with less stir shearing than the first stirring device; and

(E) a forming vessel configured to receive molten glass from the post-fining chamber and form the glass article.

11. The apparatus according to claim 10, wherein the first stirring device includes a first stir-blade configuration and the second stirring device includes a second stir blade configuration, wherein the second stir-blade configuration includes a larger molten glass shearing surface area than a molten glass shearing surface area of the first stir-blade configuration.

12. The apparatus according any one of claims 10 or 11, wherein the forming vessel comprises an isopipe configured to fusion down-draw the glass article from the molten glass.

13. The apparatus according to any one of claims 10-12, wherein the pre-fining chamber includes an inlet for receiving the molten glass from the glass melter and an uuiiei ιυι ueiiveniig me muiieii gl ss ιυ me lining unamuei , wneiein me unci is positioned at a lower elevation than the outlet.

14. The apparatus according to any one of claims 10-13, wherein the post-fining chamber includes an inlet for receiving molten glass from the fining chamber and an outlet for delivering the molten glass to the forming vessel, wherein the inlet of the post- fining chamber is positioned at a higher elevation than the outlet of the post- fining chamber.

15. The apparatus according to any one of claims 10-14, wherein the apparatus is configured with no vacuum assistance for removing gas bubbles from molten glass in the fining chamber.