JP2013512171A - Method and apparatus for producing a glass sheet having a controlled thickness - Google Patents

Abstract

A method of manufacturing a glass sheet includes providing a glass ribbon at a first temperature at which at least a portion of the glass ribbon exhibits a viscous behavior. A heat sink is provided adjacent to at least a portion of the glass ribbon at a second temperature that is lower than the first temperature. A plurality of heating elements are provided at locations where the heating elements are operable to shape the heat profile of the heat sink. Heat is transferred from this at least a portion of the glass ribbon to the heat sink, and at least a portion of the heat is absorbed by the heat sink.

Description

Explanation of related applications

  This application claims the priority of US Provisional Patent Application No. 61 / 264,017, filed on Nov. 24, 2009.

  The present invention generally relates to methods and apparatus for forming glass sheets. More specifically, the present invention relates to a method and apparatus for controlling the thickness of a glass sheet formed from molten glass.

  Patent Document 1 (SM Dockerty) describes a system for controlling the thickness of a sheet formed from molten glass. In the system of Patent Document 1, molten glass flows down the facing surface of the molding member, and this melts at the wedge bottom of the molding member to form a glass sheet. The glass sheet passes between a pair of opposing housings, each housing having a front wall facing the glass sheet. The front wall is made of a material having a high thermal conductivity, a low expansion coefficient, and a low emissivity, such as silicon carbide. A fluid conduit is arranged in the housing, wherein the nozzles of the fluid conduit are positioned on the back of the front wall in spaced relation. Each fluid conduit has an associated flow meter with a control valve and connected to the manifold. Each fluid conduit supplies cooling or heating fluid to the back area of the adjacent front wall. Typically, the fluid supplied is air. In order to control the thickness of the glass sheet, heat exchange by thermal radiation occurs between the glass sheet and the front wall. If the glass sheet thickness waveform indicates that a specific area across the glass sheet width is thicker than desired, the glass sheet zone adjacent to the thicker area is cooled, i.e., the thinner area is removed. Cool and correct the thickness waveform. The fluid conduit corresponding to this adjacent zone is driven to cool the adjacent zone (ie, the thinner area). This patent also proposes supplying heated fluid to the back of the front wall instead of supplying cooling fluid. In this case, the heated fluid will be supplied from the fluid conduit corresponding to the thicker area. This reduces the viscosity of the thicker area and then becomes thinner. Heated fluid may be supplied in association with the electrical windings in the fluid conduit.

US Pat. No. 3,682,609

  The device described above limits the resolution of the device's field of view by using convective cooling of the intervening walls that later diffuses the effect by its heat conduction. Higher resolution control is required for the glass ribbon being formed.

  The present invention satisfies this and other needs.

  Several aspects of the invention are disclosed herein. It should be understood that these aspects may or may not overlap with each other. That is, part of one aspect may be included within the scope of another aspect, and vice versa. Unless the opposite is indicated in the context, different aspects shall be considered to overlap with each other within a scope.

  Each aspect is described by a number of embodiments, which may further include one or more specific embodiments. It should be understood that these embodiments may or may not overlap each other. That is, a portion of one embodiment, or a specific embodiment thereof, may or may not be included within the scope of another embodiment, or a specific embodiment thereof. And vice versa. Unless the contrary is indicated in the context, different embodiments shall be deemed to overlap with each other within the scope.

  That is, according to the first aspect of the present invention, a method for producing a glass sheet comprises: (A) providing a glass ribbon at a first temperature at which at least a portion of the glass ribbon exhibits viscous behavior; (B) glass Providing a heat sink at a second temperature adjacent to at least a portion of the ribbon, (C) providing a plurality of heating elements in a position where the heating elements are operable to shape the heat profile of the heat sink. And (D) transferring heat from this at least a portion of the glass ribbon to the heat sink to absorb at least a portion of the heat to the heat sink.

  In certain embodiments of the first aspect of the invention, the second temperature of step (B) is lower than the first temperature, so that at least a portion of the glass ribbon is cooled by a heat sink.

  In certain embodiments of the first aspect of the invention, the second temperature in step (B) is higher than the first temperature, so that at least a portion of the glass ribbon is preferentially heated by the heat sink.

  In certain embodiments of the first aspect of the invention, in step (C), the heating element is embedded in a heat sink.

In certain embodiments of the first aspect of the present invention, the method selectively adjusts the output of each heating element so that heat is differentially absorbed by the heat sink in (E) step (D). Forming a thermal profile of the heat sink in a particular embodiment of the first aspect of the invention, in step (E), from each of a plurality of areas on this at least a portion of the glass ribbon, The output of each heating element is selectively adjusted so that an amount of heat that is inversely proportional to the thickness is transferred.

  In certain embodiments of the first aspect of the present invention, in step (E), heat transferred from the thinner area of this at least a portion of the glass ribbon is more than that of this at least a portion of the glass ribbon. The output of each heating element is selectively adjusted so that more heat is transferred from the thicker area.

  In certain embodiments of the first aspect of the present invention, in step (E), an amount of heat proportional to the temperature of each area is transferred from each of the plurality of areas on this at least a portion of the glass ribbon. The output of each heating element is selectively adjusted.

  In certain embodiments of the first aspect of the present invention, in step (E), heat transferred from a higher temperature area of this at least part of the glass ribbon is more of this at least part of the glass ribbon. The output of each heating element is selectively adjusted so that more heat is transferred from the cooler area.

  In a particular embodiment of the first aspect of the invention, the method comprises (F) monitoring the heat profile of the heat sink and further utilizing the results of this monitoring to output the output of each heating element in step (E). The method further includes the step of selectively adjusting.

  In certain embodiments of the first aspect of the invention, the method further comprises (G) supplying a cooling fluid to selected points of the heat sink to alter the shape of the heat profile of the heat sink.

  In certain embodiments of the first aspect of the invention, the method further comprises the step of (H) moving the glass ribbon relative to the heat sink.

  In certain embodiments of the first aspect of the invention, step (H) is performed simultaneously with step (D).

  In a particular embodiment of the first aspect of the present invention, step (A) comprises (A1) providing a separate flow of molten glass and further fusing the separate flow of molten glass at the wedge bottom of the forming member. To form a glass ribbon.

  In certain embodiments of the first aspect of the invention, in step (D), this at least a portion of the glass ribbon is proximate the wedge bottom.

  In certain embodiments of the first aspect of the invention, in step (D), at least a portion of the glass ribbon is below the wedge bottom.

  According to a second aspect of the present invention, there is provided an apparatus for producing a glass sheet, the apparatus comprising: (i) a forming member for forming a glass ribbon comprising a wedge-shaped portion having a wedge bottom; A molded member that forms a glass ribbon by fusing a separate stream of molten glass at the wedge bottom, (ii) a heat sink, such that the heat sink can absorb heat from at least a portion of the glass ribbon. A heat sink, and (iii) a plurality of heating elements in contact with or adjacent to the heat sink, and further operable to shape the heat profile of the heat sink, A plurality of heating elements. The surface of the heat sink has a thermal field that covers at least a portion of the surface of the glass ribbon.

  In certain embodiments of the second aspect of the present invention, the apparatus further comprises a plurality of tubes that supply cooling fluid to selected points of the heat sink. Advantageously, the tube is located behind the heat sink and not in the thermal field of view of the glass ribbon.

  In a particular embodiment of the second aspect of the invention, the heat sink is placed at a position below the wedge bottom. In certain embodiments, the plate has a flat surface facing the glass ribbon.

  In a particular embodiment of the second aspect of the present invention, the heat sink comprises a plate comprising a ceramic material having a thermal conductivity of at least 1/3 of silicon carbide at the operating temperature of the heat sink.

  In certain embodiments of the second aspect of the invention, the apparatus comprises a plate comprising silicon carbide and / or silicon nitride.

  In certain embodiments of the second aspect of the present invention, the heating element is embedded in a heat sink.

  In certain embodiments of the second aspect of the present invention, the heating element is located behind the heat sink and not within the thermal field of view of the glass ribbon.

  In certain embodiments of the second aspect of the invention, the heating element is a resistance heating element.

  In certain embodiments of the second aspect of the present invention, the apparatus further comprises a plurality of temperature sensors coupled to the heat sink for monitoring the heat profile of the heat sink.

  In certain embodiments of the second aspect of the invention, the temperature sensor is a thermocouple.

  In certain embodiments of the second aspect of the invention, the apparatus further comprises a controller that selectively adjusts the output of each heating element based on the output of each temperature sensor.

  In certain embodiments of the second aspect of the present invention, the apparatus further comprises a sensor for collecting ribbon thickness distribution information before the ribbon enters the heat field of the heat sink, and the thickness distribution information. Are sent to a controller that selectively adjusts the output of each heating element and / or each cooling tube.

  These and other aspects of the invention are described in more detail below.

  The following is a description of the figures contained in the accompanying drawings. The figures are not necessarily drawn to scale, and certain features and figures may be illustrated on an enlarged scale or schematic for clarity and brevity.

Schematic showing an apparatus for producing a glass sheet having a controlled thickness in an embodiment of the present invention. Schematic which shows the cross section of the heat sink for differentially absorbing heat from the glass ribbon part in one embodiment of the present invention Schematic showing a cross-section of a coated heating element used with the heat sink of FIG. 2 in one embodiment of the present invention. 2 is a block diagram of an apparatus for controlling the thermal profile of the heat sink of FIG. 2 in one embodiment of the invention. Schematic illustrating a technique that can differentially absorb heat from the glass ribbon portion using the heat sink of FIG.

  The present invention will now be described in detail with reference to the accompanying drawings. In this detailed description, numerous specific details will be set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well-known features and / or process steps may not be described in detail so as not to unnecessarily obscure the present invention. Further, similar or identical reference numerals may be used to identify common or similar elements.

  As used herein, “heat sink” refers to a device that regulates the temperature of a device or system by absorbing and / or irradiating heat from and to the environment.

  FIG. 1 shows an apparatus 100 for forming a glass ribbon 113 having a width W and a thickness T. The apparatus 100 includes a downdraw molding member 101 with a wedge-shaped portion having merging surfaces 103, 105 that terminate at a wedge bottom 107. First, the glass ribbon 113 starts as two molten glass streams 109 and 111 that flow down the joining surfaces 103 and 105 of the molding member 101, and then fuses at the position of the wedge bottom 107 to form a glass sheet. For example, molten glass is fed into the groove of molded member 101 and melted in a known manner as described in US Pat. Nos. 1,829,641 and 3,338,696. By causing the glass to overflow from the grooves, molten glass streams 109, 111 are formed. As indicated by an arrow 108, the glass ribbon 113 is drawn from the wedge bottom 107 into a sheet shape. When the glass ribbon 113 is drawn from the wedge bottom portion 107, the glass ribbon 113 is cooled and the glass transitions from a viscous state to an elastic state. The cooling pattern of the glass ribbon 113 in the viscous state affects the thickness profile of the glass ribbon 113 in the elastic state. Therefore, it is important to control the cooling of the glass in the viscous state in order to obtain a desired thickness profile in the elastic state.

  The apparatus 100 includes a cooling device 115 made of a heat sink 201, a plurality of heating elements 207 for heating the heat sink 201, a plurality of temperature sensors 209 that monitor the temperature distribution in the heat sink 201, and a cooling fluid jet on the heat sink 201. A plurality of pipes 120 to be supplied are included. In operation, the heat sink 201 is positioned adjacent to a portion 121 of the glass ribbon 113. The heat sink 201 is kept at a lower temperature than the glass ribbon portion 121, so that heat moves from the glass ribbon portion 121 to the heat sink 201 and is absorbed into the heat sink 201. The heating element 207 is used to shape the heat profile of the heat sink 201. How to shape the heat profile of the heat sink 201 depends on the temperature profile (or thickness profile) of the glass ribbon portion 121.

  Consider the hypothetical example shown in FIG. The glass ribbon portion 121 has areas 501, 503, 505, and 506, and the temperatures are T501, T503, T505, and T506, respectively. T501, T503, T505, and T506 can vary along three dimensions, but for simplicity, T501, T503, T505, and T506 are considered to be single values. Here, it is assumed that T501> T503> T505> T506, that is, the temperature distribution of the glass ribbon portion 121 is not uniform, and further that it is a problem to make the temperature distribution in the glass ribbon portion 121 uniform. . In this case, the heat profile of the heat sink 201 can be shaped so that the heat sink 201 differentially absorbs heat from the glass ribbon portion 121 until T501≈T503≈T505≈T506. At this time, it is assumed that the heat sink 201 has areas 507, 509, 511, and 513, and the temperatures are T507, T509, T511, and T513, respectively. Each heat sink area 507, 509, 511, 513 has one or more associated heating elements 207 and one or more associated temperature sensors 209. Further assume that the heat sink is sufficiently close to the glass ribbon 121 so that the area 507 absorbs heat from the glass ribbon area 501 as indicated by arrows 515, 517, 519, and 520, respectively. The heat sink area 509 absorbs heat from the glass ribbon area 503, the heat sink area 511 absorbs heat from the glass ribbon area 505, and the heat sink area 513 absorbs heat from the glass ribbon area 506. In order to achieve T501≈T503≈T505≈T506 in the glass ribbon portion 121, T501, T503, T505, and T506 are each set to some quantity a, b, c with a relationship of a> b> c> d. , And d must be reduced. Heating element 207 in heat sink areas 507, 509, 511, 513 so that T507, T509, T511, T513 are appropriately set to absorb the desired amount of heat from glass ribbon areas 501, 503, 505, and 506, respectively. The output of can be adjusted. Typically, the following relationship applies: T507 <T509 <T511 <T513. Adjusting the temperature distribution across the heat sink 201 so that the heat sink 201 can differentially absorb heat from the glass ribbon portion 121 is referred to as shaping the heat profile of the heat sink 201.

  Another way of thinking about the glass ribbon portion 121 is that the glass ribbon portion 121 has a high temperature area and a low temperature area. In order to make the temperature profile of the glass ribbon portion 121 constant, it is necessary to transfer more heat from the high temperature area than from the low temperature area. A heat sink 201 can be used to control this heat transfer. By providing the heat sink 201 with a relatively low temperature area and a relatively high temperature area, the heat sink 201 heats the glass ribbon portion 121 in a differential manner so that the temperature distribution in the glass ribbon portion 121 becomes more constant. Can be absorbed. Alternatively, the glass ribbon portion 121 can be considered to have a thick area and a thin area. To keep the thickness profile of the glass ribbon portion 121 constant, more heat is transferred from the thin area and less heat is transferred from the thick area. Again, the heat sink 201 can be designed to differentially absorb heat from the glass ribbon portion 121 so that the thickness across the glass ribbon portion 121 is more uniform.

  Since the heat sink 201 has a molded thermal profile, heat can be differentially absorbed from the glass ribbon portion 121. The heat profile of the heat sink 201 can be actively shaped through control of the heating element 207. For example, a particular heating element 207 can be controlled to make a particular area of the heat sink 201 relatively hot, while a particular heating element 207 can be controlled to make a particular area of the heat sink 201 relatively cold. . A tube (120 in FIG. 1) may be used to further supply a cooling fluid jet to several points on the heat sink 201 to affect the shaping of the heat profile of the heat sink 201. However, the profile shaping resolution that can be obtained when the cooling fluid jet is used alone is not as fine as the resolution possible with the heating element 207.

  The heat sink 201 is a mass of a material having a high heat capacity and a low thermal expansion. The surface of the heat sink 201 is continuous in a facing relationship with the glass ribbon portion 121. Therefore, the heat sink 201 can generate a heat dump without being disturbed by the glass ribbon portion 121. In certain embodiments, the heat sink 201 is plate-shaped, which may be flat as shown. Alternatively, the heat sink 201 may have other shapes as further described below. In certain embodiments, the material of the heat sink 201 is a ceramic material, examples of which include, but are not limited to, silicon nitride and silicon carbide. Silicon carbide is an excellent heat spreader. Silicon nitride has excellent high temperature strength, creep resistance, and oxidation resistance. Silicon nitride also has excellent thermal shock resistance when compared to most ceramic materials including silicon carbide. The thermal conductivity of silicon nitride is less than half that of silicon carbide. Therefore, silicon nitride has the potential to provide a finer temperature profile than silicon carbide. Other types of heat sink materials that are not based on ceramic, such as materials based on alloys or nanomaterials, may be used for the heat sink 201.

  FIG. 2 shows a cross section of the heat sink 201. The illustrated heating element 207 is embedded in the heat sink 201. The heating element 207 may be embedded in the heat sink 201 by, for example, forming a hole in the heat sink 201 and inserting the heating element 207 into the hole. In an alternative embodiment, the heating element 207 may be adjacent to and in close proximity to the surface of the heat sink 201 rather than embedded within the heat sink 201. This alternative embodiment facilitates replacement of defective heating elements. In certain embodiments, the heating element 207 is a resistive heating element made from a high temperature material. The high temperature material may be an inert material, ie a material that resists oxidation. Examples of suitable high temperature materials include platinum, platinum alloys, and noble metal alloys. In certain embodiments, each heating element 207 is a conductive wire made from a high temperature material. These heating elements 207 may be linear heating elements or non-linear heating elements. If the heating element 207 is a linear heating element, fine adjustment of the temperature profile across the heat sink 201 can be achieved by reducing the spacing between adjacent heating elements 207.

  When the heating element 207 is embedded in the heat sink 201, the heating element 207 may be embedded together with the coating material or may be embedded without the coating material depending on the material of the heat sink 201. For example, if the material of the heat sink 201 is an electrical insulator such as silicon nitride, the heating element does not require a coating material. On the other hand, when the material of the heat sink 201 is an electrical conductor such as silicon carbide, a coating material is required for the heating element. FIG. 3 illustrates an example coated heating element 207 that includes a high temperature conductor (or wire) 300, surrounded by a high temperature insulator 302 and further surrounded by a high temperature coating 304. It is a thing. For example, the high temperature conductor 300 may be made of platinum, a platinum alloy, a noble metal alloy, or the like. The high temperature insulator 302 may be made of magnesium oxide, aluminum oxide, hafnium oxide, beryllium oxide, or the like. The high temperature coating 304 may be made from a platinum alloy or other high temperature metal or alloy. Other materials suitable for use as high temperature conductors, high temperature insulators, and high temperature coatings can also be used.

  In FIG. 2, the temperature sensor 209 is at least partially embedded in the heat sink 201. The temperature sensor 209 may be embedded in the heat sink 201 by, for example, forming a hole in the heat sink plate 201 and inserting the temperature sensor 209 at least partially into the hole. In an alternative embodiment, the temperature sensor 209 may be mounted on the surface of the heat sink 201. The temperature sensor 209 may be, for example, a thermocouple or a thermistor. Typically, the temperature sensor 209 is desirably made from a material that is inert in an oxidizing atmosphere and resistant to high temperatures. When the temperature sensor 209 is a high temperature thermocouple, the thermocouple may be made of platinum, a platinum alloy, or a noble metal alloy. As with the heating element 207, electrical isolation may or may not be required between the temperature sensor 209, such as a thermocouple, and the heat sink 201, depending on the material of the heat sink 201. There is also. When electrical isolation is required, such as when the material of the heat sink 201 is silicon carbide, a technique similar to coating the heating element 207 can be used for the temperature sensor 209.

  The heating element 207 is designed to generate heat. For example, if the heating element 207 is a resistance heating element, power can be supplied to the heating element 207 to cause the heating element 207 to generate heat. The heat generated by the heating element 207 is dissipated to the heat sink 201. FIG. 4 shows the temperature sensor 209 and the heating element 207 connected to the controller 400. The controller 400 has three functions: temperature reading, power teaching, and power output. The controller 400 receives the output signal from the temperature sensor 209 and uses this output signal to create the current heat profile of the heat sink 201. The current thermal profile of the heat sink 201 is compared with the desired thermal profile of the heat sink 201. Controller 400 then adjusts the output power to heating element 207 accordingly. Through the signal output control feedback loop, the controller 400 adjusts the current thermal profile to match the desired thermal profile. The desired thermal profile of the heat sink 201 is determined by the temperature or thickness profile of the glass ribbon portion (121 in FIG. 1) as described above.

  In FIG. 2, the heat sink 201 is illustrated as a flat rectangular plate. In an alternative embodiment, the surface of the heat sink 201 facing the heat sink 201, ie, the glass ribbon portion (121 in FIG. 1), is a radial shape factor between the heat sink 201 and the glass ribbon portion (121 in FIG. 1). In order to maximize the above, it may have a non-flat shape, for example, a curved shape. The radiation shape factor is the ratio of thermal energy that leaves the surface of the glass ribbon portion (121 in FIG. 1) and reaches the surface of the heat sink 201, and is exclusively between the heat sink 201 and the glass ribbon portion (121 in FIG. 1). Determined from geometric considerations. The thickness of the heat sink 201 depends on the conductivity of the heat sink material. In general, the lower the thermal conductivity of the heat sink material, the thinner the heat sink needs to be. For example, a heat sink made of silicon nitride can provide a heat flux (q) equivalent to silicon carbide at half the thickness of a heat sink made of silicon carbide. Where q = KΔT / X, K is the thermal conductivity, ΔT is the temperature difference, and X is the thickness of the substrate. For example, if 1 inch (2.54 cm) thick silicon carbide is required to supply a particular q, then 0.5 inch (1.27 cm) silicon nitride to supply the same q Will be necessary.

  Referring to FIG. 1, the method of making a glass sheet includes forming a glass ribbon 113 as described above. While the glass ribbon 113 is being molded, the heat sink 201 is positioned adjacent to the portion 121 of the glass ribbon 113 such that heat is transferred from the glass ribbon portion 121 to the heat sink 201 by radiation. The heat sink 201 essentially serves as a heat dump for the glass ribbon portion 121. The temperature of the glass ribbon portion 121 is typically the temperature at which the glass exhibits viscous behavior, while the temperature of the heat sink 201 is lower than the temperature of the glass ribbon portion 121. The position of the glass ribbon portion 121 is typically in the vicinity of the wedge bottom 107 (above or below the wedge bottom 107), and at this position the glass is still likely to be viscous. The width of the heat sink 201 determines the width of the glass ribbon portion 121 that is a target when the heat sink 201 functions as a heat dump. Typically, the width of the heat sink 201 is equal to the width of the glass ribbon 113, but in other examples it may be shorter or longer than the width of the glass ribbon 113.

  The heat sink 201 differentially absorbs heat from the glass ribbon portion 121. This differential absorption is determined by the heat profile of the heat sink 201, which is controlled by the heating element 207 and optionally by the cooling fluid jet from the tube 120 as described above. Can do. In certain embodiments, the heat profile of the heat sink 201 is such that it transfers an amount of heat from a different area of the glass ribbon 121 to the heat sink 201 in an amount that is inversely proportional to the glass thickness of that area. In certain embodiments, the heat profile of the heat sink 201 is such that the heat transferred from the thinner area of the glass ribbon portion 121 to the heat sink is greater than the heat transferred from the thicker area of the glass ribbon portion 121 to the heat sink 201. The thermal profile is such that it increases. The net result will be that the heat sink 201 differentially absorbs heat from the glass ribbon portion 121 so that the temperature profile or thickness profile of the glass ribbon portion 121 is more uniform.

  As the glass ribbon 113 moves away from the wedge bottom 107 of the forming member 101, the glass ribbon portion 121 having the modified temperature profile or thickness profile moves with the glass ribbon 113. A new glass ribbon portion replaces the previous glass ribbon portion 121. Similar to that described above with respect to the previous glass ribbon portion 121, the heat sink 201 can be used to differentially absorb heat from the new glass ribbon portion. This process may be repeated for all new glass ribbon portions positioned adjacent to the heat sink 201 as the glass ribbon 113 continuously moves away from the wedge bottom 107. In certain embodiments, a sensor or sensors are introduced to monitor the thickness of the glass ribbon over the heat sink and across the width of the glass ribbon before the ribbon enters the heat sink thermal field of view. The thickness distribution information is sent to the heating element and / or cooling fluid tube control system to preferentially adjust the temperature distribution of the heat sink. This effectively adjusts the temperature and / or thickness of the glass ribbon as it passes through the heat sink thermal field of view.

  The heat sink 201 having a molded thermal profile may be used alone to control the thickness of the glass ribbon portion 121. Alternatively, a heat sink 201 having a shaped thermal profile may be used with a cooling fluid jet from the tube 120 to control the thickness of the glass ribbon portion 121. As previously described, the cooling fluid jet will affect the shape of the heat profile of the heat sink 201, but this effect can be of an overall nature, while the heating element 207 reduces the shape of the heat profile. It would be worth it as a fine adjustment. The tube 120 may be similar to the fluid conduit described in U.S. Pat. No. 3,682,609, and is connected to a manifold (not shown) via a flow meter (not shown) and a control valve (not shown). None) may be connected. The fluid supplied by the tube 120 may be air. The heat sink 201 is used in place of the intervening wall in US Pat. No. 3,682,609. Note that shaping the thermal profile of heat sink 201 to achieve thickness control of glass ribbon portion 121 requires some information regarding the temperature distribution or thickness profile of glass ribbon portion 121. This may include active measurements on the glass ribbon portion 121 or may be based on past data obtained using a specific set of process settings and parameters.

  The heat sink 201 may be a single unit having a width that sufficiently includes the width of the glass ribbon portion 121, and the width of the glass ribbon portion 121 may be the same as the width W of the glass ribbon 113, or May be different. Alternatively, the heat sink 201 may have a modular structure. In this case, a plurality of modules may be arranged next to each other to form a heat sink 201 having a desired width. Alternatively, a plurality of modules may be arranged separately only in a portion where the thickness control of the glass ribbon 113 is required.

  In certain embodiments, the temperature of the heat sink may be controlled so that at least the portion of the heat sink surface facing the glass ribbon has a higher temperature than the corresponding area of the glass ribbon within the heat sink thermal field of view. Is possible. In these embodiments, heat is transferred from the heat sink to the glass ribbon, effectively increasing the temperature of the exposed area and the viscosity of the glass, and its thickness while the glass ribbon is being stretched. Decrease.

  Although the present invention has been described above with reference to a limited number of embodiments, it will benefit from the present disclosure that other embodiments may be devised that do not depart from the scope of the invention disclosed herein. It will be apparent to those skilled in the art. Accordingly, the scope of the invention should be limited only by the attached claims.

DESCRIPTION OF SYMBOLS 101 Molding member 113 Glass ribbon 120 Tube 121 Glass ribbon part 201 Heat sink 207 Heating element 209 Temperature sensor

Claims (12)

A method of manufacturing a glass sheet,
(A) providing a glass ribbon at a first temperature at which at least a portion of the glass ribbon exhibits viscous behavior;
(B) providing a heat sink at a second temperature adjacent to the at least a portion of the glass ribbon;
(C) providing a plurality of heating elements in a position where the heating elements are operable to shape a heat profile of the heat sink; and
(D) transferring heat from the at least a portion of the glass ribbon to the heat sink to absorb at least a portion of the heat to the heat sink;
A method comprising the steps of:   The method of claim 1, wherein in step (C), the heating element is embedded in the heat sink. (E) shaping the thermal profile of the heat sink by selectively adjusting the output of each heating element such that heat is differentially absorbed by the heat sink in step (D);
The method according to claim 1 or 2, further comprising:   In step (E), more heat is transferred from a thinner area of the at least part of the glass ribbon than heat transferred from a thicker area of the at least part of the glass ribbon. The method of claim 3, wherein the output of each heating element is selectively adjusted.   In step (E), the heat transferred from the hotter area of the at least part of the glass ribbon is more than the heat transferred from the cooler area of the at least part of the glass ribbon. 4. The method of claim 3, wherein the output of each heating element is selectively adjusted to increase. (F) monitoring the thermal profile of the heat sink and further using the result of the monitoring to selectively adjust the output of each heating element in step (E);
The method of claim 3, further comprising:   The method of claim 1 or 2, wherein in step (D), the at least a portion of the glass ribbon is in the vicinity of the wedge bottom. In an apparatus for producing a glass sheet,
A molding member for forming a glass ribbon, comprising a wedge-shaped portion having a wedge bottom, wherein the glass ribbon is formed by fusing a separated flow of molten glass at the wedge bottom,
A heat sink, positioned near the wedge bottom, such that the heat sink can absorb heat from at least a portion of the glass ribbon; and
A plurality of heating elements in contact with or adjacent to the heat sink, and further operable to shape a heat profile of the heat sink;
A device characterized by comprising:   9. The apparatus of claim 8, wherein the heat sink is a plate comprising a ceramic material having a thermal conductivity of at least 1/3 of silicon carbide at an operating temperature of the heat sink.   The apparatus according to claim 8 or 9, further comprising a plurality of temperature sensors coupled to the heat sink for monitoring the thermal profile of the heat sink.   The apparatus of claim 10, further comprising a controller that selectively adjusts the output of each heating element based on the output of each temperature sensor.   The ribbon further comprises a sensor for collecting ribbon thickness distribution information before entering the heat sink thermal field of view, and the thickness distribution information is output from each heating element and / or each cooling tube. 10. A device according to claim 8 or 9, wherein the device is sent to a controller that selectively adjusts.

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