The present disclosure relates generally to a thermally enhanced glass manufacturing apparatus and method and more specifically to a glass manufacturing apparatus and method that is thermally enhanced for high glass flow rates.
In the manufacture of glass materials, such as flat glass substrates for display applications, such as LCD televisions and handheld electronic devices, there is a continual desire to increase molten glass flow rates. As flow rates of molten glass increase, more energy is imputed into the manufacturing process. As more energy in imputed into the manufacturing process, the temperature of the glass inside of a glass manufacturing apparatus will increase, all else being equal. Such increased temperature may lead to at least one of many potential undesirable effects including reduced stability of the molten glass as well as one or more undesirable product attributes.
When the glass manufacturing process involves fusion drawn glass, attempts to maintain the baseline cooling curve at varying flow rates (to maintain desired glass properties) can include at least one changes in elements designed to effectuate controlled cooling and changes relating to thermal insulation configurations. However, such techniques may not be adequate to address increasingly high molten glass flow rates and reduced average formed glass thicknesses. In addition, it would be advantageous to be able to have increased capacity to tailor the thermal profile of the cooling curve in both the vertical and horizontal directions, especially at high molten glass flow rates and reduced glass thicknesses, under which conditions it is more difficult to tailor the cooling curve in either direction.
Disclosed herein is an apparatus for producing a glass article. The apparatus includes a cooling mechanism in at least one wall of the apparatus that enhances radiation heat transfer between molten glass and the wall of the apparatus and is tunable in both the vertical and horizontal directions. The cooling mechanism provides increased radiation heat transfer from the glass ribbon to a wall of the apparatus relative to a condition where such cooling mechanism is absent. The apparatus also includes a heating mechanism that affects radiation heat transfer between molten glass and the wall of the apparatus, is tunable in both the vertical and horizontal directions, and is independently operable from the cooling mechanism. The heating mechanism provides decreased radiation heat transfer from the glass ribbon to a wall of the apparatus relative to a condition where such heating mechanism is absent.
Also disclosed herein is a method of producing a glass article that includes forming the glass article in an apparatus. The apparatus includes a cooling mechanism in at least one wall of the apparatus that enhances radiation heat transfer between molten glass and the wall of the apparatus and is tunable in both the vertical and horizontal directions. The cooling mechanism provides increased radiation heat transfer from the glass ribbon to a wall of the apparatus relative to a condition where such cooling mechanism is absent. The apparatus also includes a heating mechanism that affects radiation heat transfer between molten glass and the wall of the apparatus, is tunable in both the vertical and horizontal directions, and is independently operable from the cooling mechanism. The heating mechanism provides decreased radiation heat transfer from the glass ribbon to a wall of the apparatus relative to a condition where such heating mechanism is absent.
Additional features and advantages of these and other embodiments will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present embodiments of the present disclosure, and are intended to provide an overview or framework for understanding the nature and character of the embodiments as claimed. The accompanying drawings are included to provide a further understanding of these and other embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of these and other embodiments, and together with the description serve to explain the principles and operations thereof.
Reference will now be made to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
As used herein, the term “in at least one wall of the apparatus” refers to an area that at least partially encloses an area of a glass manufacturing apparatus where the glass is cooled from at least temperatures including and below the glass working point to temperatures including and below the glass strain point and includes elements and materials in or on the wall, whether integral to the wall or attached to or within the wall, including one or more baffles.
As used herein, the term “cooling mechanism that enhances radiation heat transfer” refers to a mechanism that provides increased radiation heat transfer from the glass ribbon to a wall of the apparatus relative to a condition where such cooling mechanism is absent.
As used herein, the term “heating mechanism that affects radiation heat transfer” refers to a mechanism that provides decreased radiation heat transfer from the glass ribbon to a wall of the apparatus relative to a condition where such heating mechanism is absent. Notably, the heating mechanism that affects radiation heat transfer may include heating elements that are at a higher, lower, or approximately equal temperature than the temperature of the portion of the glass ribbon that is in closest proximity to the heating elements.
As used herein, the term “working point” refers to the temperature in degrees Celsius at which the viscosity of the glass is 104 poise.
As used herein, the term “softening point” refers to the temperature in degrees Celsius at which the viscosity of the glass is 107.6 poise.
As used herein, the term “annealing point” refers to the temperature in degrees Celsius at which the viscosity of the glass is 1013 poise.
As used herein, the term “strain point” refers to the temperature in degrees Celsius at which the viscosity of the glass is 1014.5 poise.
Embodiments disclosed herein can enable improved cooling of glass, such as glass sheets, at increasingly high glass flow rates and reduced thicknesses, for example, at glass temperatures between 200° C. and the working point of the glass, which can broadly be defined as a temperature range that encompasses the settling zone of the glass or the temperature range in which various properties are imputed into the glass depending on, for example, the composition and cooling rate of the glass at a given temperature. Such temperature range can also include a temperature range between the softening point and the strain point of the glass, including temperature ranges between the softening point and annealing point of the glass and between the annealing point and the strain point of the glass.
The glass forming apparatus 101 can also include a fining vessel 127, such as a fining tube, located downstream from the melting vessel 105 and fluidly coupled to the melting vessel 105 by way of a first connecting tube 129. A mixing vessel 131, such as a stir chamber, can also be located downstream from the fining vessel 127 and a delivery vessel 133, such as a bowl, may be located downstream from the mixing vessel 131. As shown, a second connecting tube 135 can couple the fining vessel 127 to the mixing vessel 131 and a third connecting tube 137 can couple the mixing vessel 131 to the delivery vessel 133. As further illustrated, a downcomer 139 can be positioned to deliver glass melt 121 from the delivery vessel 133 to an inlet 141 of a forming device 143. As shown, the melting vessel 105, fining vessel 127, mixing vessel 131, delivery vessel 133, and forming device 143 are examples of glass melt stations that may be located in series along the glass forming apparatus 101.
The melting vessel 105 is typically made from a refractory material, such as refractory (e.g. ceramic) brick. The glass forming apparatus 101 may further include components that are typically made from platinum or platinum-containing metals such as platinum-rhodium, platinum-iridium and combinations thereof, but which may also comprise such refractory metals such 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 first connecting tube 129, the fining vessel 127 (e.g., finer tube), the second connecting tube 135, the standpipe 123, the mixing vessel 131 (e.g., a stir chamber), the third connecting tube 137, the delivery vessel 133 (e.g., a bowl), the downcomer 139 and the inlet 141. The forming device 143 is made from a ceramic material, such as the refractory, and is designed to form the glass ribbon 103.
As shown, the trough 201 can have a depth “D” between a top of the weir and a lower portion of the trough 201 that varies along an axis 209 although the depth may be substantially the same along the axis 209. Varying the depth “D” of the trough 201 may facilitate consistency in glass ribbon thickness across the width of the glass ribbon 103. In just one example, as shown in
The forming device 143 further includes a forming wedge 211 comprising a pair of downwardly inclined forming surface portions 213, 215 extending between opposed ends of the forming wedge 211. The pair of downwardly inclined forming surface portions 213, 215 converge along a downstream direction 217 to form a root 219. A draw plane 221 extends through the root 219 wherein the glass ribbon 103 may be drawn in the downstream direction 217 along the draw plane 221. As shown, the draw plane 221 can bisect the root 219 although the draw plane 221 may extend at other orientations with respect to the root 219.
The forming device 143 may optionally be provided with one or more edge directors 223 intersecting with at least one of the pair of downwardly inclined forming surface portions 213, 215. In further examples, the one or more edge directors can intersect with both downwardly inclined forming surface portions 213, 215. In further examples, an edge director can be positioned at each of the opposed ends of the forming wedge 211 wherein an edge of the glass ribbon 103 is formed by molten glass flowing off the edge director. For instance, as shown in
Each of walls 302a and 302b includes a cooling mechanism that, as described in greater detail below, enhances radiation heat transfer between molten glass and the wall of the apparatus and is tunable in both the vertical and horizontal directions. Each of walls 302a and 302b also includes a heating mechanism that, as described in greater detail below, affects radiation heat transfer between molten glass and a wall of the apparatus, is tunable in both the vertical and horizontal directions, and is independently operable from the cooling mechanism.
Specifically, in the embodiment illustrated in
Fluid flowing through the conduits may, for example, be a gas, such as air, or a liquid. In certain exemplary embodiments the fluid is a liquid, and in a particular exemplary embodiment the fluid is water.
In exemplary embodiments the fluid flowing through the conduits has a temperature of less than 100° C., such as less than 90° C., and further such as less than 80° C., including from 20° C. to 100° C., and further including from 30° C. to 90° C., and yet further including from 40° C. to 80° C.
For example, in a preferred exemplary embodiment, the fluid is water at a temperature of less than 100° C., such as less than 90° C., and further such as less than 80° C.
Fluid flowing through the conduits may flow from one side of the apparatus to the other, such as from the side closest to the inlet side of the glass forming device to the side closest to the compression side of the glass flowing device or vice versa. Alternatively, fluid may flow from near the center of each wall toward the ends of each wall (i.e., in opposite directions from the center to the ends of the walls).
Each of the conduits may be individually controlled such that fluid flowing in different conduits is at similar or different temperatures and/or flow rates. For example, in some conduits, the temperature and/or flow rate of the fluid may be at the same or different temperatures than the temperature and/or flow rate of the fluid in other conduits. Moreover, the same or different fluids may flow through different conduits. For example, a gas, such as air, may flow through at least one conduit while, in at least one other conduit, a liquid, such as water, may flow.
Still further yet, each of the conduits may extend through only a portion of the length of each wall of the apparatus. For example, each wall of the apparatus may comprise an array of rows and columns of conduits extending in the X and Y directions along the wall. Each of the conduits in the array of conduits may be individually controlled such that fluid flowing in different conduits is at similar or different temperatures and/or flow rates. For example, in some conduits, the temperature and/or flow rate of the fluid may be at the same or different temperatures than the temperature and/or flow rate of the fluid in other conduits. Moreover, the same or different fluids may flow through different conduits. For example, a gas, such as air, may flow through some conduits while, in other conduits, a liquid, such as water, may flow. In this manner, the cooling mechanism may be tunable in both the vertical and horizontal directions.
Radiation heat transfer via the cooling mechanism can be further enhanced coating each of the interiors of walls 302a and 302b (i.e., the sides of the walls that are closest to glass ribbon 103) with a high emissivity coating, such as high emissivity ceramic coatings available from Cetek Ceramic Technologies. Such high emissivity coatings can be coated on the outer surfaces of baffles, shown in
Radiation heat transfer can also be enhanced by the inclusion of at least one cooling bayonet (not shown in
Radiation heat transfer can also be enhanced by the removal of insulation baskets (not shown in
Additional heat transfer can be effected by increasing the amount of convective heat transfer within the apparatus, such as by creating at least a partial vacuum within the apparatus that thereby increases convective fluid flow, such as air flow, within the apparatus, such as between or within each of walls 302a and 302b, including fluid flow, such as air flow, within baffles 304a-d. Examples of embodiments of such enhanced convective heat transfer mechanisms are disclosed in U.S. application Ser. No. 61/829,566, the entire disclosure of which is incorporated herein by reference.
In the embodiment shown in
While
Heating elements, in certain exemplary embodiments may be electrical resistive heating elements. For example, in certain embodiments, the heating elements may comprise electrically resistive heating elements available from Kanthal. In certain embodiments, the heating elements may comprise at least one material selected from the group consisting of molybdenum disilicide (MoSi2) and alloys of iron, chromium, and aluminum (FeCrAl). Temperatures of electrical heating elements, when in operation, may, for example, range from 1,200° C. to 1,900° C., such as from 1,300° C. to 1,800° C., and further such as from 1,400° C. to 1,700° C.
Each of the heating elements may be individually controlled. For example, each of the heating elements may be controlled such that the temperature or percent power saturation of some heating elements may be the same or different than the temperature of percent power saturation of other heating elements.
Still further yet, each of the heating elements may extend through only a portion of the length of each wall of the apparatus. For example, each wall of the apparatus may comprise an array of rows and columns of heating elements extending in the X and Y directions along the wall. Each of the heating elements in the array of heating elements may be individually controlled. For example, the temperature or percent power saturation may be the same or different in some heating elements than the temperature or percent power saturation in other heating elements. In this manner, the heating mechanism may be tunable in both the vertical and horizontal directions. In this manner, the heating mechanism may also be independently operable from the cooling mechanism.
Radiation heat transfer via the heating mechanism can be further affected by positioning sufficient thermal insulation between the heating elements and the bulk of the walls of the apparatus. As shown in
While not limited to any particular material, thermal insulation, in certain exemplary embodiments, has a thermal conductivity of less than 5.0 W/mK, such as less than 2.5 W/mK, and further such as less than 1.0 W/mK, and still further such as less than 0.5 W/mK, and still yet further such as less than 0.25 W/mK at 600° C., such as from 0.1 to 5.0 W/mK, including from 0.1 to 2.0 W/mK, and further including from 0.1 to 1.0 W/mK, and still further including from 0.1 to 0.5 W/mK, and still yet further including from 0.1 to 0.25 W/mK at 600° C. Exemplary materials for thermal insulation include those comprising Fiberfrax® alumino silicate fibers from Unifrax.
Fluid flowing through the baffle conduits may, for example, be a gas, such as air, or a liquid. In certain exemplary embodiments the fluid is a liquid, and in a particular exemplary embodiment the fluid is water.
In exemplary embodiments the fluid flowing through the baffle conduits has a temperature of less than 100° C., such as less than 90° C., and further such as less than 80° C., including from 20° C. to 100° C., and further including from 30° C. to 90° C., and yet further including from 40° C. to 80° C.
For example, in a preferred exemplary embodiment, the fluid is water at a temperature of less than 100° C., such as less than 90° C., and further such as less than 80° C.
When the baffle conduits extend from one side of the wall to the other, fluid may flow from near the center of each wall toward the ends of each wall (i.e., in opposite directions from the center to the ends of the walls).
Each of the baffle conduits may be individually controlled such that fluid flowing in different baffle conduits is at similar or different temperatures and/or flow rates. For example, in some baffle conduits, the temperature and/or flow rate of the fluid may be at the same or different temperatures than the temperature and/or flow rate of the fluid in other baffle conduits. Moreover, the same or different fluids may flow through different baffle conduits. For example, a gas, such as air, may flow through at least one baffle conduit while, in at least one other baffle conduit, a liquid, such as water, may flow.
Still further yet, each of the baffle conduits may extend through only a portion of the length of each wall of the apparatus. For example, each wall of the apparatus may comprise an array of rows and columns of baffle conduits extending in the X and Y directions along the wall. Each of the baffle conduits in the array of conduits may be individually controlled such that fluid flowing in different baffle conduits is at similar or different temperatures and/or flow rates. For example, in some baffle conduits, the temperature and/or flow rate of the fluid may be at the same or different temperatures than the temperature and/or flow rate of the fluid in other baffle conduits. Moreover, the same or different fluids may flow through different baffle conduits. For example, a gas, such as air, may flow through some baffle conduits while, in other conduits, a liquid, such as water, may flow. In this manner, the cooling mechanism may be further tunable in both the vertical and horizontal directions.
Accordingly, embodiments disclosed herein include those in which the cooling mechanism comprises at least two cooling mechanism components, namely a first cooling mechanism component and a second cooling mechanism component, wherein the first cooling mechanism component includes fluid flow in a conduit that is at a relatively farther distance from the glass ribbon than the second cooling mechanism component, such as within the interior of a wall of the apparatus as shown, for example, in
When acting in concert, the first and second components of the cooling mechanism may involve fluid flows at the same or different flow rates and temperatures. For example, each wall of the apparatus may comprise an array of rows and columns of conduits of each of the first and second components of the cooling mechanism, the conduits extending in the X and Y directions along the wall. Each of the conduits of either component of the cooling mechanism may be individually controlled such that fluid flowing in different conduits is at similar or different temperatures and/or flow rates.
Embodiments disclosed herein, including those described above, can enable production of glass at increasingly high flow rates and reduced thickness, which production follows, as closely as possible, a predetermined cooling curve that enables the production of glass sheets with superior properties such as density, compaction, Young's Modulus, Specific Modulus, coefficient of thermal expansion, Poisson's Ratio, as well as low stress and warp. For example, embodiments disclosed herein can enable production of glass at increasingly high flow rates having a thickness of less than 0.5 millimeters, a density of less than 2.6 g/cm3, a Young's Modulus of at least 65 GPa, and warp of less than 100 microns.
For example, as the glass flow rate is increased, the cooling mechanism can be adjusted or tuned in at least one of the vertical and horizontal directions to extract more heat from the apparatus to compensate for the increased energy imputed into the apparatus as a result of the higher flow rate. At the same time, the heating mechanism can be adjusted or tuned in at least one of the vertical and horizontal directions to modify heat transfer between heating elements and the glass so as to enable the cooling of the glass at the increased flow rate to follow the predetermined cooling curve as closely as possible and adjust for any process drift. The cooling and heating mechanisms can also be adjusted to account not only for differing glass flow rates but also for different glass thicknesses as well as different glass compositions having different predetermined cooling curves.
In embodiments disclosed herein, a tuning algorithm can be employed, such as a process control algorithm, that, for example, accounts for the thermal response of different glass compositions at different flow rates in an apparatus and then adjusts each of the cooling and heating mechanisms in real time to enable the cooling of the glass to, as closely as possible, follow a predetermined cooling curve. In certain embodiments, the tuning algorithm would employ a computer processor. In certain embodiments, the tuning algorithm can take into account the cooling of the glass in not only down draw direction but also across the draw, thereby enabling real time controlled cooling of the glass in both the vertical and horizontal directions.
The tunability of the cooling and heating mechanisms in both the vertical and horizontal directions can be further enhanced by incorporating at least one multiphase cooling and inductive heating element into any vertical or horizontal area of the device. Such elements can be operable to heat or cool the same area of a device depending on whether the multiphase cooling system is in operation or the inductive heating system is in operation. Exemplary multiphase cooling and inductive heating systems are disclosed in U.S. application Ser. No. 14/460,447, the entire disclosure of which is incorporated herein by reference.
In the embodiment of
As noted above, embodiments disclosed herein can enable production of glass at increasingly high flow rates, which production follows, as closely as possible, a predetermined cooling curve. For example, embodiments disclosed herein can include those in which, at varying glass flow rates, the cooling mechanism and heating mechanism are configured such that the glass is cooled at a faster average cooling rate when the glass is at temperatures between the strain point of the glass and 200° C. than when the glass is at temperatures between the softening point of the glass and the strain point of the glass. Such embodiments can also include those in which, at varying glass flow rates, the cooling mechanism and heating mechanism are configured such that the glass is cooled at a faster average cooling rate when the glass is at temperatures between the working point of the glass and the softening point of the glass than when the glass is at temperatures between the softening point of the glass and the strain point of the glass. Such embodiments can additionally include those in which, at varying glass flow rates, the cooling mechanism and heating mechanism are configured such that the glass is cooled at a faster average cooling rate when the glass is at temperatures between the annealing point of the glass and the strain point of the glass than when the glass is at temperatures between the softening point of the glass and the annealing point of the glass. Such embodiments can enable the production of thin glass sheets at relatively high molten glass flow rates, such as glass sheets having a thickness of less than 0.5 millimeters, while at the same time, following a predetermined cooling curve, wherein the environment surrounding the molten glass ribbon is minimally disruptive (which is particularly important for thin glass) and, therefore, amenable to stable production of high quality product with minimal process upset.
Exemplary glass working points, while not limited, include those from 1,100° C. to 1,500° C. Exemplary glass softening points, while not limited, include those from 800° C. to 1,200° C. Exemplary glass annealing points, while not limited, include those from 550° C. to 950° C. Exemplary glass strain points, while not limited, include those from 500° C. to 900° C.
While specific embodiments disclosed herein have been described with respect to an overflow downdraw process, it is to be understood that the principle of operation of such embodiments may also be applied to other glass forming processes such as flow processes and slot draw processes.
It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of these and other embodiments provided they come within the scope of the appended claims and their equivalents.
This application claims the benefit of priority under 35 U.S.C. §365 of International Patent Application Serial No. PCT/US16/26553, filed on Apr. 8, 2016, which claims the benefit of priority under U.S. Provisional Application Ser. No. 62/148,870, filed on Apr. 17, 2015, the content of are relied upon and incorporated herein by reference in their entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2016/026553 | 4/8/2016 | WO | 00 |
Number | Date | Country | |
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62148870 | Apr 2015 | US |