JP5974145B2 - Apparatus and method for controlling thickness of flowing molten glass ribbon - Google Patents

Description

Explanation of related applications

  This application claims the benefit of US Provisional Patent Application No. 61 / 348,512, filed May 26, 2010. The contents of this document and the entire disclosure of the publications, patents, and patent documents mentioned in this document are incorporated by reference.

  The present invention relates to a method and apparatus for controlling the thickness of a molten glass stream, and more particularly to controlling the thickness of a continuous molten glass stream in a downdraw glass sheet forming process.

  When the molten glass is drawn into a sheet, the glass is stretched, ie weakened, from the initial delivery thickness to the final sheet thickness. In the overflow downdraw process, the molten glass flows down along the opposing mating surfaces of the forming member and is drawn from its bottom or bottom edge as a single glass ribbon. The initial thickness of the glass ribbon is measured near the lower edge of the molded member. This lower end edge corresponds to a stretching line in this operation. Thereafter, the glass sheets are divided one by one from the free end of the stretched ribbon.

  In the updraw and downdraw processes, the final sheet thickness characteristics are determined during the weakening process by both the initial thickness uniformity and the glass viscosity uniformity. In both of these processes, obtaining a ribbon with a uniform thickness has always been a challenge. That is, the final sheet thickness variation is due to inaccurate measurement, incomplete glass contact surface of the molded member, or unstable temperature environment of the glass toward the drawing line. This can be caused by an incomplete viscosity profile of the flowing glass.

  Glass sheet thickness variation is a problem that has been considered to be inherent in the sheet drawing process in the industry, such as wedge shape, long period wavy variation, and short period wavy variation. Can appear as a kind of defect. The wedge shape is a significant variation in thickness where one edge of the ribbon or sheet is thicker than the other edge. Long undulations are undulations with significant amplitude and spread, such as over a few inches, and can be evaluated by measuring the ribbon along a path in a direction across the stretch direction. Short undulations are of small amplitude and pitch, for example about 3 inches or less, and generally overlap with long undulations.

  In order to produce an undistorted glass sheet, it has been found necessary to minimize or compensate for local temperature fluctuations or fluctuations in and around the glass in the ribbon forming zone. Such local fluctuations in the vicinity of the draw line produce waves or other thick or thin portions that extend in the longitudinal direction within the vertically stretched ribbon. This longitudinal wave or thickness variation causes aberrations that are very undesirable from an optical point of view, especially when viewing an object through the glass from an acute angle to the wave.

  A conventional method for controlling such a thickness variation includes a step of flowing air to the molten glass from the cooling tubes arranged along the longitudinal direction of the molded body. Straight cooling pipes were arranged at the same intervals along the longitudinal direction of the molded body, and were positioned so that the central longitudinal axis of each pipe was perpendicular to a vertical plane passing through the bottom. In addition, the cooling tube was covered with a tubular outer shield. That is, these tubes were fixed and positioned in a state associated with the forming body and the glass flow.

  Unfortunately, the position of the glass ribbon thickness defect may not be stable over time, or the lateral position of the ribbon itself may not be constant. That is, if the cooling tube is a pre-positioned fixed one, it can be properly positioned in the first case, but because the defect or ribbon has moved, the second time can effectively control the thickness. There is a possibility that the position is not suitable.

  Other methods include the step of using a cooling tube attached to a fixture, the fixture extending the range of one tube by swinging the cooling tube about one or more axes. It was provided to enhance the cooling effect by the cooling gas flow.

  The present invention relates to an improved method and apparatus therefor that significantly reduces the general type of local thickness variation, which is perceived as short wavy variations having a width of a few inches or less.

  In forming a glass sheet from molten glass, a heat sink is positioned in the forming area in close proximity to the surface of the flowing molten glass to absorb heat energy from individual local portions of the molten glass. In particular, the heat sink is positioned close to the draw line or bottom to control local thickness variations in the sheet, thereby achieving a uniform glass thickness. The heat sink or cooling member may be disposed within a fixture configured to rotate or pivot the heat sink (ie, the cooling member) about at least one axis, thereby against the flowing glass (and molded body). It becomes possible to change the way the cooling member is presented. This aids in removing heat from the flowing molten glass and helps change the magnitude of this removed heat depending on properties, such as thickness, downstream of the glass. The amount of thermal energy extracted by the cooling member (and thereby cooled by the cooling member) by inserting the cooling member towards the flowing molten glass or pulling it away from the flowing molten glass. The viscosity and thickness of the local region) can be varied, or the cooling member can be rotated or pivoted about an axis. This cooling can be accomplished without directing the cooling gas from the cooling member towards the flowing molten glass as was done in conventional local cooling methods.

  According to one embodiment of the present invention, an apparatus for forming a continuous molten glass ribbon in a downdraw glass manufacturing process is disclosed, and a forming body having a confluence forming surface that merges at the bottom is disposed around the forming body. Enclosure, at least one thickness control unit connected to the enclosure for changing the local temperature of the molten glass, which extends close to the molten glass stream flowing over the molded body A thickness control unit with an elongated cooling member, wherein the thickness control unit does not include a mechanism for supplying an air flow through the cooling member (i.e., from the cooling member to molten glass). The airflow is not directed towards the The cooling member is preferably rotatable with respect to the vertical axis, which means that the cooling member can be pivoted or swung with respect to the vertical axis, thereby changing the angular orientation of the cooling member with respect to the forming body. The cooling member has a tip closest to the molten glass flow and a proximal end farthest from the molten glass (relative to the tip). It is preferable that the distance between the tip of the elongated cooling member and the molded body can be changed, for example, by pulling the cooling member away from the molten glass or inserting it closer to the molten glass. . Such a distance between the tip and the molded body (and the molten glass flow) can also be realized by turning the cooling member with respect to the vertical axis described above. The cooling member may be a tube having a hollow interior or a solid bar. However, with a solid bar, there is no danger of air leakage between the interior of the enclosure and the environment outside the enclosure through the hollow interior, and better heat conduction can be realized. In this document, a rod is intended to mean an elongated body and is not to be construed to mean only a cylindrical rod. Indeed, the elongate body may have another shape, and the shape of the bar may vary along the length of the body. In some cases, the tip of the elongated body (cooling member) may be I-shaped, different from the area of the elongated body immediately adjacent to the tip. For example, the width of the tip is larger than the width of the base end of the cooling member. The tip may be bulbous, but may have a uniform cylindrical shape as the elongated body is moved longitudinally away from the bulbous tip. In other words, the shape of the tip is different from the shape of the cooling member adjacent to the tip.

  The apparatus may further include a plurality of thickness control units and a plurality of elongate cooling members arranged horizontally adjacent to the longitudinal direction of the molded body, wherein the array is relative to the bottom of the molded body. And has a substantially uniform height. In other embodiments, the distance between the tips of the plurality of cooling members and the molded body may not be uniform. This can occur by varying the vertical height of the individual thickness control units, or by changing the tip of each cooling member by rotating the cooling member with respect to a non-vertical rotation axis, eg, a horizontal axis. Can result. The tip of the cooling member has a viscosity of the molten glass close to the tip within a range between 35,000 poise (about 3,500 Pa · s) and 1,000,000 poise (100,000 Pa · s). As such, it is preferably positioned.

  In some embodiments, the apparatus may further comprise a temperature corrector positioned near the cooling member, the temperature corrector changing the temperature of the cooling member and thereby the tip of the cooling member. And the temperature difference between the continuous ribbons of molten glass. For example, the temperature corrector may be an electric heating coil or a cooling coil in which a coolant flow is flowing. A temperature corrector is used to change the temperature of the cooling member, thereby changing the temperature difference between the cooling member (and in particular the tip of the cooling member) and the molten glass stream proximate to the tip of the cooling member. .

  According to another embodiment, a method for controlling the thickness of a continuous glass ribbon in a fusion downdraw process is described, the method comprising flowing molten glass over a merged molding surface at the bottom of a molded body, Forming a glass ribbon, changing a viscosity of a localized area of the flowing molten glass using an elongated cooling member placed in close proximity to the flowing molten glass, and further comprising: It is characterized in that the viscosity of this local area of molten molten glass is changed without flowing a cooling gas flow from the elongated cooling member towards the flowing molten glass. The elongate cooling member has a proximal end and a distal end, the distal end being closer to the molten glass flow than the proximal end, and the shape of the distal end is different from the shape of the elongate cooling member adjacent to the distal end. The method may include a plurality of elongate cooling members, wherein the distance between the tips of the plurality of elongate cooling members and the flowing molten glass is not uniform. This can occur, for example, when individual cooling members are rotated or swiveled with respect to a rotational axis such as a vertical axis. In some embodiments, the distance between the elongate cooling member (its tip) and the flowing molten glass is such that the elongate cooling member is inserted toward or away from the flowing glass. It can be changed by pulling.

  In certain embodiments, the angle between the longitudinal axis of the elongated cooling member and the vertical plane including the bottom is varied. That is, the cooling member may be rotated or swiveled with respect to an axis passing through the cooling member that is perpendicular to the central longitudinal axis of the cooling member, whereby the central longitudinal axis and the molded body that is proximate to the cooling member ( Therefore, the angle with the flowing molten glass) is changed.

  In certain embodiments, the central longitudinal axis of the at least one cooling member is perpendicular to the vertical plane including the bottom. In other words, the central longitudinal axis of the cooling member is perpendicular to the bottom.

  In certain other embodiments, depending on the measured thickness of the glass sheet obtained from the glass ribbon, the temperature of the cooling member is adjusted to vary the amount of heat extracted from the flowing molten glass. Change. For example, a cooling coil or heating coil may be in contact with or in close proximity to the cooling member, thereby changing the temperature of the cooling member and further between the tip of the cooling member and the molten glass stream proximate to the tip. Change the temperature difference. This may be performed in response to a thickness measurement performed downstream of the bottom of the molded body. In yet another embodiment, depending on the measured thickness of the glass sheet obtained from the glass ribbon, the angular position of the cooling member is changed to change the amount of heat extracted from the flowing molten glass. It may be changed.

  In yet another embodiment, depending on the measured thickness of the glass sheet obtained from the glass ribbon, the tip of the cooling member and the melt are used to vary the amount of heat extracted from the flowing molten glass. Change the distance between the glass flow.

  The angular position, the distance from the tip of the molten glass stream, or the temperature of the cooling member may be changed independently, or may be changed in various combinations as required.

  Additional features and advantages of the invention will be apparent from the detailed description that follows, and in part will be readily apparent to those skilled in the art from the description, or the invention may be as described herein. It will be recognized by doing. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. It should be understood that the various features of the invention disclosed in this document and in the drawings can be used in any and all combinations.

FIG. 3 is a cross-sectional view of an exemplary fusion downdraw apparatus for producing glass sheets, showing the arrangement of cooling members for controlling the local thickness of the glass ribbon flowing from the forming body. FIG. 2 is a side view of the apparatus of FIG. 1 wherein a plurality of thickness control units with elongated cooling members are horizontally disposed over at least a portion of the apparatus length, i.e., within the length of the molded body. A figure showing that it is arranged in an array FIG. 2 is a side view of the apparatus of FIG. 1 wherein a plurality of thickness control units with elongated cooling members are horizontally disposed over at least a portion of the apparatus length, i.e., within the length of the molded body. Arranged in an array state, where the vertical height of each thickness control unit with respect to the bottom of the molded body is not uniform FIG. 2 is a cross-sectional view of a portion of a cooling member used in the apparatus of FIG. 1, showing the arrangement of the cooling member within a fixture that helps at least laterally roll the elongated cooling member. FIG. 2 is a front view of a fixture for manipulating an elongated cooling member, showing a bracket for attaching the fixture to the apparatus of FIG. 1 is a perspective view showing a swivel member connected to an elongated cooling member forming a swivel member-cooling member unit according to an embodiment of the present invention; FIG. 7 is a view of the swivel member-cooling member unit of FIG. 6 viewed straight from the end of the elongated cooling member, showing the arrangement of keys in the keyway for connecting the swivel member to the platform. Partial cross section of the platform showing the placement of the key in the platform keyway FIG. 7 is a perspective view of the swivel member-cooling member unit of FIG. 6, showing a lateral roll of the elongated cooling member due to rotation of the swivel member about the vertical axis. FIG. 7 is a perspective view of the swivel member-cooling member unit of FIG. 6, showing a vertical pitching of the elongated cooling member due to the rotation of the swivel member with respect to the horizontal axis. Cylindrical revolving member-perspective view of cooling member unit FIG. 6 is a cross-sectional view of a portion of the fixture of FIG. 5 showing a complementary mating surface of the receptacle member. FIG. 5 illustrates an exemplary pivot member-cooling member unit according to an embodiment of the present invention with an elongate cooling member having an arcuate sheet-like tip. The top view of the several cooling member arranged in the array, Comprising: The figure which showed that the distance between the front-end | tip of each cooling member and the flowing molten glass is not uniform over an array A top view of a plurality of cooling members arranged in an array, showing that the angular orientation of each cooling member is not uniform across the array

  In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art who has benefited from the present disclosure that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods, and materials may be omitted so as not to obscure the description of the present invention. Finally, wherever applicable, the same reference numbers indicate similar elements.

  Illustrated in FIG. 1 is an apparatus 10 for drawing a glass ribbon by an exemplary fusion downdraw process. The apparatus 10 includes a molded body 12 with an upper groove or trough 14 disposed therein. The molded body 12 includes merged molding surfaces 16a, 16b that meet at a lower edge, ie, a drawing line 18, and the molten glass is drawn from the molding body from the position of the drawing line. The lower edge 18 is sometimes referred to as the bottom 18. When the molten glass 20 is supplied to the trough 14, the molten glass overflows from the trough so as to flow over the upper edge of the trough, and descends the merge forming surfaces 16a and 16b as two separated flows of the molten glass. The separated flow of molten glass recombines or fuses at the bottom of the molded body and continues downward from the bottom in direction 21 as a single glass ribbon 22. Thus, this process is sometimes referred to as a fusion process or a fusion downdraw process. The portion of the molten glass that is in contact with the forming surface of the forming body 12 is positioned inside the ribbon that extends from the bottom 18 and the outer surface of the ribbon remains uncontaminated. The glass ribbon 22 is transferred from the viscous liquid in the molded body 12 to the viscoelastic material, and finally transferred to the elastic material. When the ribbon reaches an elastic state, the ribbon is divided by, for example, scoring and folding to form individual glass sheets or panes 23.

  In order to control the thermal environment surrounding the molten glass, the molded body 12 is positioned within a refractory enclosure or muffle 24. The muffle 24 includes a structural support member 26 disposed around the muffle refractory material. A muffle door 28 is positioned below the muffle 24 along the opposing surface of the glass ribbon 22, and the muffle door 28 can move inward or outward along the support rail 30. Any space between the muffle 24 and the muffle door 28 may be filled with a suitable refractory insulation 32, such as inorganic wool fibers, to prevent air leakage or ventilation. An outer shielding member 34 is attached to the muffle 24 and extends downwardly like a skirt from the muffle 24 to the top of the muffle door 28. The outer shielding member 34 is typically formed from a metal such as stainless steel. The shielding member 34 helps to further eliminate the possibility of ventilation due to the exchange of air between the atmosphere inside the muffle and the atmosphere outside the muffle. However, since each muffle door is configured to move inward or outward relative to the glass ribbon, the outer shielding member 34 is not permanently attached to the muffle door 28. In some embodiments, the shielding member 34 may be an integral part of the muffle 24, for example, an extension of the support member 26.

  A plurality of thickness control units 38 are positioned near the bottom 18 along the side surface of the molded body 12. For example, the thickness control unit 38 may be connected to the outer shielding member 34. Each thickness control unit 38 includes an elongate cooling member 40, which is spaced from an adjacent elongate cooling member of an adjacent thickness control unit, preferably a substantially horizontal plane 41 (FIG. 2). However, the positions of the elongate cooling members need not all be in the same horizontal plane. For example, in some embodiments, the elongate cooling members may be displaced vertically if desired (FIG. 3). Each cooling member is vertically adjacent to a region of the glass ribbon that is in a viscosity range between about 35,000 poise (about 3,500 Pa · s) and 1,000,000 poise (100,000 Pa · s). It is preferable that it is located in. Each thickness control unit may further include a fixture 42 (FIG. 4) that surrounds a portion of each cooling member and optionally connects the cooling member to the outer shielding member. Each thickness control unit can be coupled to the outer shielding member 34 using a bracket 44 of the fixture 42 and the elongated cooling members are maintained in spaced relation on the outer shielding member 34 by the bracket. The The end of each elongate cooling member 40 is in close proximity to the molded body 12 and more particularly in close proximity to the bottom 18. For example, each elongate cooling member may be within about 6 cm to about 13 cm of the molded body.

  Each elongate cooling member 40 is formed of a material that can withstand deformation at a high temperature in the volume 36, for example, greater than 1250 ° C. The cooling member, when in its simplest form, is an elongate body that extends close to the forming body, particularly close to the bottom of the forming body, preferably less than about 10 cm from the surface of the molten glass. It is. The cooling member may be a solid rod or a hollow member such as a hollow tube. In some embodiments, the cooling member may be glass or quartz, ceramic or glass ceramic. In another embodiment, the cooling member may be made of metal such as a metal rod. The solid cooling element can prevent heated air present in the muffle from escaping through the cooling element, thereby affecting the overall thermal environment inside the muffle. Is advantageously reduced. However, this can also be achieved with a hollow tube having a baffle or barrier inside the tube. Furthermore, the thermal mass of the solid cooling member is larger than that of the hollow tube, and it is more effective for extracting thermal energy from the flowing molten glass. Metal cooling elements generally have greater heat transfer properties (conduct more heat energy from the molten glass) than ceramic or glass cooling elements, but melt larger temperature and viscosity variations than required This rapid heat extraction may be undesirable because it produces in glass. In addition, in some glass manufacturing processes, metal cooling members may not actually be used due to the high temperatures experienced when in close proximity to the molten glass.

  The elongate cooling member 40 is typically circular in cross-section perpendicular to the longitudinal axis of the cooling member (see, eg, FIG. 7), but may have other geometric shapes. For example, the cooling member may have an oval cross section, a square cross section, a triangular cross section, or the like. Further, the cooling member may be substantially flat, which may form a generally rigid strip having a predetermined finite horizontal width. The thickness of each strip may vary over the length of the strip. The appropriate vertical thickness of each strip can be easily determined to help prevent strip bending and other deformations.

  Each cooling element, when brought in close proximity to the molten glass stream descending from the forming body, affects the temperature of the small localized area of the flowing molten glass, thereby causing the viscosity of the molten glass and the final It acts as an adjustable heat sink that affects the local thickness of the molten glass. By local thickness is meant the thickness of a flowing molten glass along a horizontal strip of glass that is less than about 2 cm wide. The cooling member according to embodiments disclosed herein simply adjusts the degree of proximity of the cooling member to the glass flow without using a flowing gas emanating from the cooling member, as used in conventional methods. Note that the thickness control is achieved by. That is, the cooling member acts by utilizing the thermal conductivity of the cooling member. This is largely due to radiant heat loss from the flowing glass to the cooling member.

  Referring to FIG. 7, each cooling member 40 may be coupled to a pivot member 46, wherein each pivot member includes a passage 48 that extends through the passage. The cooling member may be tightly bonded within the swivel member passage 48, for example using high temperature cement, or it may be moved inward and outward relative to the molten glass stream descending from the forming body. The cooling member may be held using other methods such as a compression joint or a clamp. For example, in certain embodiments, the cooling member 40 may be closer to the surface of the glass that flows closest to the cooling member, or the cooling member may be pulled away from the surface of the flowing molten glass. May be. The degree of proximity from the front end of the cooling member to the surface of the flowing glass material affects the amount of heat energy that the cooling member removes from the molten glass. The cooling member may be oriented such that the vertical axis of the cooling member is perpendicular to the vertical plane 47 passing through the bottom of the molded body, or the vertical axis of the cooling member is inclined with respect to the vertical plane 47. May be. If the cooling member 40 is a flat strip, the longitudinal axis of the strip extends longitudinally through the strip and is equidistant from both side edges of the strip, and between the upper and lower surfaces of the strip Interpreted as equidistant axes (assuming that the strip has uniform properties, ie, uniform thickness and width).

  According to one embodiment, best shown in FIGS. 5 and 6, each pivot member 46 may be substantially spherical, for example, a metal sphere defining the aforementioned passage 48. . Substantially spherical means that the majority of the outer surface of the swivel member is spherical, or at least that contact portion that is in contact with the mating surface of the receptacle member, more fully described herein below, is spherical. means. Other parts of the swivel member that do not contact the complementary mating surfaces of the receptacle member are spherical (or complementary shapes) unless these other surface portions prevent movement of the swivel member along the desired rotation. It can not be.

  The pivot member 46 may be coupled to the platform 50, which includes a high precision rotary stage 51 that allows the pivot member to accurately move with respect to the platform rotation axis 52. The pivot member 46 may be fixed to the platform 50 with a key so that no relative rotational movement about the vertical axis 52 occurs between the pivot member and the platform. Accordingly, the key 54 may be positioned between the pivot member 46 and the platform 50 using corresponding slots or keyways 56, 58 provided in the platform and pivot member, respectively (see FIGS. 7 and 8 for clarity). To remove the key). The key 54 may be secured in either (or both) the platform keyway or the pivot member keyway. Alternatively, the key 54 may be firmly fixed to one of the keyway of the platform or the keyway of the pivot member, and in the other, it may be simply slidably fitted. For example, the key 54 may be secured within the keyway 58 of the spherical pivot member and slidably aligned within a corresponding complementary keyway 56 on the platform 50 so that the spherical pivot member is vertical. It is possible to rotate not only with respect to the rotating shaft 52 but also with respect to the horizontal rotating shaft 53, and two rotational degrees of freedom are given to the turning member and the cooling member. FIGS. 9 and 10 show the motions related to these two degrees of freedom, ie, FIG. 9 shows horizontal swing or roll, and FIG. 10 shows vertical swing or pitch. However, since the space between the muffle doors is generally very narrow, the rotation of the pivoting member about the horizontal axis of rotation, i.e. pitch, is generally limited by contact between the cooling member and the muffle elements and / or the muffle door. . As will be further described below, it is easy to see that pivoting member 46 can be moved in various directions by removing the key and relying on the clamping force and cannot be limited to simple pitch or roll. Let's go.

  If the swivel member 46 and the cooling member 40 are integrated into a single unit and this unit is not permanently connected to the platform 50, then the swivel member and cooling member combination can be easily replaced. For example, a particular cooling member can be easily replaced by removing the damaged swivel member-cooling member combination and simply inserting a new swivel member-cooling member unit. If a key-keyway connection is used between the platform and the new pivot member-cooling member, this connection will place the new pivot member and cooling member in the same exact angular orientation as the first pivot member. Can do. That is, the swivel member-cooling member unit can be removed without disturbing the positions of the platform 50 and the key 54, and a new swivel member-cooling member unit can be reinstalled at the same horizontal angular position as the damaged unit. it can.

  If only rotation about the vertical axis of rotation is desired (rolling), the pivot member 46 may be cylindrical, with the central longitudinal axis of the cylindrical pivot member coinciding with the platform axis of rotation 52 (FIG. 11). In this case, the mating surface of the receptacle member, which will be described in more detail below in this document, should be cylindrical, complementary to the cylindrical pivot member.

  The elongate cooling member 40 extends through the passage 48 of the pivot member 46, wherein the first portion 60 of the cooling member 40 extends from the pivot member in a direction toward the flowing molten glass and The two portions 62 extend from the pivot member 46 away from the glass ribbon. The cooling member 40 includes two ends, a proximal end 64 disposed furthest from the molten glass stream and a distal end 66 closest to the molten glass stream. The proximal end 64 may be heated or cooled using a suitable temperature modifier 67 if desired. Thereby, the thickness control provided by a particular cooling member can be adjusted by changing the temperature of the cooling member, and the tip of the cooling member and the molten glass flow close to the tip The temperature difference between can also be changed. For example, the proximal end of the cooling member 40 may be coupled to an optional heating coil or cooling coil (FIG. 1). The coil uses current to heat the cooling member or to cool the cooling member using a flowing coolant that circulates in the cooling coil and carries heat away from the cooling member. For example, cold water may be circulated through the cooling coil. The coolant may then flow through a heat exchanger to remove heat from the coolant. By increasing the temperature difference between the cooling member and the flowing glass and / or molded body, the cooling effect of the cooling member can be increased.

  Conversely, the cooling member may be heated using electrical windings or coils, thereby delaying the ability of the cooling member to absorb heat from the flowing glass and molded body. By reducing the temperature difference between the cooling member and the flowing glass and / or molded body, the cooling effect of the cooling member can be reduced.

  The heating and cooling of individual cooling members by temperature modifiers such as the heating and cooling coils described above may be incorporated into the feedback loop. In this feedback loop, the local thickness of the glass ribbon is measured near the bottom of the ribbon downstream of the cooling member, or in a glass sheet divided from the ribbon, and the thickness data obtained is used to determine one or more cooling members. May be adjusted. The glass thickness can be determined using, for example, laser triangulation. A suitable measuring instrument for measuring thickness is the GTS2 thickness and profile measurement sensor from LMI Technologies. For example, if the thickness of the local area of the glass ribbon is less than the target thickness, the coolant to the cooling coil is moved by moving the cooling member closer to the glass or thermodynamically coupled to the cooling member The effectiveness of the cooling member can be increased by increasing the flow or by reducing the temperature of the coolant flow. If desired, a controller 71 may be provided to automate the feedback loop. The controller 71 communicates with the thickness measurement detector via the control line 73 and further communicates via the control line 75 with one or more actuators (not shown) connected to the cooling member of each thickness control unit. (See FIG. 3). It should be noted that other temperature modifiers, such as electrical strip heaters, thermoelectric cooling elements, etc. may be used to vary the temperature of the cooling member, and the cooling coil diagram of FIG. 1 is not intended to be limiting.

  As best seen in FIG. 12, the fixture 42 further comprises a front or first receptacle member 74 and a rear or second receptacle member 76. Here, for the sake of clarity, the swivel member 46 is omitted. The first receptacle member 74 includes an inner surface 78, at least a portion of which is complementary to a portion of the pivot member. When the opening 80 extends through the thickness of the first receptacle member and the pivot member 46 is in contact with a complementary portion of the interior surface 78 of the receptacle, the cooling member 40 passes through the opening 80. Extend. The opening 80 is sized to allow movement of the pivoting member and cooling member without interfering with its intended range of movement. That is, the size of the opening 80 is such that the pivoting member can rotate at least about the shaft 52 so that the cooling member 40 can swing or roll within the opening. The cooling member 40 preferably swings freely over an angle of at least about 40 degrees. Similarly, the second receptacle member 76 includes an inner surface 82 that is at least partially complementary to the pivot member 46 and a second opening 84 through which the cooling member 40 extends. Thus, the second portion of the cooling member 40 can swing when the turning member 46 rotates.

  The rear receiving member 76 is connected to the front receiving member 74 so that the swiveling member 46 disposed between the front receiving member and the rear receiving member is stably held. For example, the front receptacle member and the rear receptacle member may be coupled together using bolts, screws, clips, or other suitable connection method so that the pivot member 46 is clamped between the receptacle members. For example, in FIG. 12, the illustrated receptacle members 74 and 76 are connected by bolts. The swivel member 46 is initially positioned so that the cooling member 40 is within a predetermined proximity and position range from the flowing molten glass, and the clamping element (such as a bolt) is tightened to secure the swivel member and the cooling member. It may be locked in the desired orientation.

  The ability of the pivot member according to this embodiment to rotate about the axis 52 and thereby “swing” the cooling member 40 through a horizontal arc is the width of the molten glass compared to the fixed cooling member. Helps to reduce the number of thickness control units 38 required to reach For example, the elongate cooling member 40 can be rotated through the pivot member 46 over at least about 10 °, 20 °, 30 °, or more than 40 °. In addition, relying on the heat transfer characteristics of the cooling member rather than the release of the cooling gas makes it easier to install and maintain the cooling member (eg, an external pipe for delivering cooling gas, Gas measurement is not used).

  Compared to the conventional cooling method, according to the present embodiment, the cooling member 40 can be spaced more than the fixed cooling member. If cooling is required in a specific area of the flowing molten glass due to thickness disturbances, the cooling member closest to the defect is cooled by rotating the platform 50, ie thereby By rotating the member 40, the cooling member can be brought into close proximity to the defect area by swinging it laterally to a predetermined position. Furthermore, each cooling member is pulled (away from the molten glass flow) or inserted (toward the molten glass flow) to change the distance between the molten glass flow and the tip of the cooling member. Also good. As a result, the number of openings to the volume within the muffle is reduced. As the number of openings decreases, the risk of uncontrolled ventilation due to leakage into (or out of) volume 36 surrounding muffle 24 is reduced. Each elongate cooling member need not align its movement with the other cooling members, either with respect to rotation through the pivot member 46, or with respect to inward or outward movement toward or away from the molten glass stream. .

  In some embodiments, the elongate cooling member 40 is straight and has a uniform cross-sectional shape perpendicular to its longitudinal axis. However, in other embodiments, each cooling member may have a modified tip that has a different shape than the portion of the cooling member adjacent to the tip. The pivot member may include, for example, a crescent tip, a partially cylindrical tip, or a disc tip. FIG. 13 shows an elongate cooling member 40 having an arcuate end, similar to a portion of a cylindrical wall. The cooling member may include a more complex tip, such as a combination of different geometric shapes, which is desirable to control the local area of the flowing glass. The tip of such a modified cooling member is wider (in the direction perpendicular to the longitudinal axis 88 of the elongate cooling member) than the proximal end of the cooling member.

  From the previous disclosure, using the positioning of the individual cooling elements, the local thickness of the glass ribbon drawn from the molten glass, and finally the thickness of the individual glass sheet or pane divided from this ribbon. It should be clear that it can be controlled effectively. According to embodiments described herein, individual cooling members can be rotated (turned) about one or more axes to change the angular orientation of the cooling member relative to the molded body and molten glass. For example, individual cooling members can be pivoted about a vertical axis, thereby creating a lateral swing. Individual cooling members can also be inserted closer to the molten glass stream to shorten the distance between the tip of the cooling member and the molten glass stream. Alternatively, individual cooling members can be pulled, which increases the distance between the molten glass stream and the tip of the cooling member. Thus, the angular orientation of individual cooling members, and the distance from the tip to the molten glass flow of each individual cooling member, is the angular orientation and tip distance of another cooling member contained within the array of these cooling members. Can be obtained independently. That is, it can provide a cooling profile across the width of the flowing glass that is suitable for individual glass production settings. FIG. 14 depicts an exemplary array of cooling members viewed from above, where the individual cooling members are positioned at different distances from the molten glass stream (in this case, the downward molten glass stream). Is represented by an edge view of the plane 100). Although each cooling member is represented as a straight rod in FIG. 14, the size and shape of each cooling member can be varied as required by the above description. Similarly, FIG. 15 depicts an array of cooling members having different angular orientations to produce different cooling profiles across the width of the molten glass stream, which is also viewed from above. It is what I saw. In FIG. 15, the cooling members are shown adjusted with respect to both the distance from the tip of each cooling member to the molten glass flow and the angular position.

  Exemplary, non-limiting embodiments are shown below.

C1. An apparatus for forming a continuous ribbon of molten glass in a downdraw glass manufacturing process,
A molded body with a merged molding surface that merges at the bottom,
An enclosure disposed around the molded body;
At least one thickness control unit connected to the enclosure for changing the local temperature of the molten glass, elongate extending very close to the molten glass stream flowing over the forming body Thickness control unit with cooling member,
And an air flow is not directed from the cooling member toward the molten glass.

  C2. The apparatus of C1, wherein the cooling member is rotatable about a vertical axis.

  C3. The apparatus according to C1 or C2, wherein the cooling member has a tip closest to the molten glass flow and is capable of changing a distance between the tip of the elongate cooling member and the molded body.

  C4. The apparatus according to any one of C1 to C3, wherein the cooling member is a solid bar.

  C5. C1 to C4, wherein the cooling member has a tip closest to the molten glass flow, and the shape of the tip is different from the shape of the cooling member adjacent to the tip. Equipment.

  C6. The apparatus according to C5, wherein a width of the distal end is larger than a width of a proximal end of the cooling member.

  C7. The apparatus according to any one of C1 to C6, further comprising a plurality of elongate cooling members, wherein the plurality of elongate cooling members are arranged horizontally adjacent to a longitudinal direction of the molded body.

  C8. The apparatus according to C7, wherein a distance between the tips of the plurality of cooling members and the molded body is not uniform.

  C9. The viscosity of the molten glass in which the tip of the cooling member is close to the tip is in a range between 35,000 poise (about 3,500 Pa · s) and 1,000,000 poise (100,000 Pa · s). The apparatus according to any one of C1 to C8, wherein the apparatus is positioned so as to be within.

  C10. A temperature corrector, wherein the temperature corrector is configured to change the temperature of the cooling member and thereby change the temperature difference between the tip of the cooling member and the continuous molten glass ribbon. The apparatus according to any one of C1 to C9, characterized in that

  C11. A plurality of cooling members are further provided, and a vertical height of the first cooling member of the plurality of cooling members with respect to the bottom portion is different from a vertical height of the second cooling member of the plurality of cooling members with respect to the bottom portion. The apparatus according to any one of C1 to C10, characterized in that:

C12. A method for controlling the thickness of a continuous ribbon of molten glass in a fusion downdraw process,
A step of forming a glass ribbon by pouring molten glass onto a merged molding surface intersecting at the bottom of the molded body;
Changing the viscosity of a localized area of the flowing molten glass using an elongated cooling member placed in close proximity to the flowing molten glass;
And further changing the viscosity of the local area of the flowing molten glass toward the flowing molten glass without diverting a cooling gas flow from the elongated cooling member. .

  C13. The elongated cooling member has a proximal end and a distal end, the distal end is closer to the molten glass flow than the proximal end, and the shape of the distal end is different from the shape of the elongated cooling member adjacent to the distal end. The method according to C12, wherein:

  C14. The method of C12 or C13, wherein the distance between the elongate cooling member and the flowing molten glass is varied.

  C15. The method according to any one of C12 to C14, wherein the angle between the longitudinal axis of the elongate cooling member and the vertical plane including the bottom is varied.

  C16. The method according to any one of C12 to C15, wherein a part of the longitudinal axis of the at least one cooling member is perpendicular to a vertical plane including the bottom.

  C17. The method further includes changing the temperature of the cooling member in order to change the amount of heat extracted from the flowing molten glass according to the measured thickness of the glass sheet obtained from the glass ribbon. The method according to any one of C12 to C16, characterized in that:

  C18. Changing the angular position of the cooling member to change the amount of heat extracted from the flowing molten glass according to the measured thickness of the glass sheet obtained from the glass ribbon. A method according to any one of C12 to C17, characterized in that it comprises.

  C19. In order to change the amount of heat extracted from the flowing molten glass according to the measured thickness of the glass sheet obtained from the glass ribbon, the tip of the cooling member and the flowing molten glass The method according to any one of C12 to C18, further comprising the step of changing a distance between and.

  C20. The changing step includes a plurality of elongated cooling members, each cooling member having a proximal end and a distal end, and a distance between the distal ends of the plurality of elongated cooling members and the flowing molten glass. The method according to any one of C12 to C19, wherein is not uniform.

  It should be emphasized that the above-described embodiments of the present invention, particularly any "preferred" embodiments, are merely possible examples and are merely illustrative for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without substantially departing from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.

DESCRIPTION OF SYMBOLS 12 Molding body 22 Glass ribbon 24 Muffle 38 Thickness control unit 40 Cooling member 42 Fixing tool 46 Turning member 47 Vertical plane 50 Platform 52 Vertical axis 54 Key 56, 58 Key groove 64 Base end 66 Tip 67 Temperature corrector

Claims (9)

A method for controlling the thickness of a continuous ribbon of molten glass in a fusion downdraw process,
A step of forming a glass ribbon by pouring molten glass onto a merged molding surface intersecting at the bottom of the molded body;
Changing the viscosity of the local area of the flowing molten glass using an elongated cooling member that is rotatable about a vertical axis and placed in close proximity to the flowing molten glass;
And further changing the viscosity of the local area of the flowing molten glass toward the flowing molten glass without diverting a cooling gas flow from the elongated cooling member. .   The elongated cooling member has a proximal end and a distal end, the distal end is closer to the molten glass flow than the proximal end, and the shape of the distal end is different from the shape of the elongated cooling member adjacent to the distal end. The method of claim 1 wherein:   3. A method according to claim 1 or 2, wherein the distance between the elongated cooling member and the flowing molten glass is varied.   4. A method according to claim 1, wherein the angle between the longitudinal axis of the elongate cooling member and the vertical plane including the bottom is varied.   The method according to claim 1, wherein a part of the longitudinal axis of at least one cooling member is perpendicular to a vertical plane including the bottom.   The method further includes changing the temperature of the cooling member in order to change the amount of heat extracted from the flowing molten glass according to the measured thickness of the glass sheet obtained from the glass ribbon. 6. A method according to any one of claims 1 to 5, characterized in that   Changing the angular position of the cooling member to change the amount of heat extracted from the flowing molten glass according to the measured thickness of the glass sheet obtained from the glass ribbon. 7. The method according to any one of claims 1 to 6, comprising:   In order to change the amount of heat extracted from the flowing molten glass according to the measured thickness of the glass sheet obtained from the glass ribbon, the tip of the cooling member and the flowing molten glass The method according to any one of claims 1 to 7, further comprising the step of changing the distance between the two.   The changing step includes a plurality of elongated cooling members, each cooling member having a proximal end and a distal end, and a distance between the distal ends of the plurality of elongated cooling members and the flowing molten glass. 9. A method according to any one of claims 1 to 8, characterized in that is not uniform.

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