KR20120086709A - Method and apparatus for controlling sheet thickness - Google Patents

Abstract

A method of making a thickness profile of a glass ribbon is presented. For a selected strip of glass ribbon that exhibits viscous action, one or more regions in the strip are found that have a thickness that is outside the target thickness for the strip. Radiant heat is then applied to one or more regions of the strip to reduce the viscosity of the glass in the one or more regions.

Description

Sheet thickness control method and apparatus therefor {Method and apparatus for controlling sheet thickness}

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

U.S. Patent No. 3,682,609 discloses a system for controlling the thickness of sheets molded from molten glass. In the system of US Pat. No. 3,682,609, molten glass flows down both sides of the molding member and merges in the wedge-shaped root of the molding member to form a glass sheet. The glass sheet passes between a pair of opposing housings having a front wall facing the glass sheet. The front wall is made of a material having high conductivity against heat, low expansion, and low emissivity, such as silicon carbide. The fluid conduit tube is disposed in the housing with the nozzles of the fluid conduit tube positioned in a spaced apart relationship at the rear of the front wall. Each fluid conduit has an associated flow meter, which includes a control valve and is connected to the manifold. Each fluid conduit tube transfers cooling or heated fluid to the back region of the adjacent front wall. Typically, the conveyed fluid is air. Heat exchange by heat radiation is performed between the glass sheet and the front wall to control the thickness of the glass sheet. If it has been found by thickness tracking of the glass sheet that a particular area across the width of the glass sheet is thicker than necessary, tracking by the cooling zone of the glass sheet adjacent to the thicker area, ie by cooling the thinner area Thickness is corrected. The fluid conduit tube corresponding to the adjacent zone is actuated to cool the adjacent zone (ie, the thinner region). The patent also proposes to transfer the heated fluid to the rear side of the front wall as an alternative to transferring the cooling fluid. In this case, the heated fluid may be transported by the fluid conduit tube corresponding to the thicker area. This will reduce the viscosity in the thicker areas and make the thicker areas thinner. The heated fluid may be provided by an electrical winding associated with the fluid conduit tube.

The system described above has long been used to control the thickness of shaped sheets from molten glass. Although the system is effective, there are several problems with using the system. For example, cooling fluid, typically air, carried by a fluid conduit tube may sometimes leak into the draw where the glass sheet is located. This leakage can lead to uncontrollable heat loss of the glass sheet and uneven thickness of the glass sheet. The system cannot be easily applied to numerical control systems and feedback systems, which are necessary for automatic control. The resolution of the field of view of the system is limited by the use of convective cooling of the intermediate wall, which spreads the effects of thermal conduction. Attempts to produce the formed thermal representation are ineffective because of this diffusion.

Thus, in accordance with one aspect of the present invention, a method for controlling the thickness profile of a glass ribbon is presented. The present invention provides a method for making selected strips of glass ribbon exhibiting viscous action, the method comprising: finding one or more regions in a strip having a thickness that is outside the target thickness for the strip; And (B) applying radiant heat to said one or more regions of said strip to reduce the viscosity of the glass in one or more regions.

In a particular embodiment of the first aspect of the invention, the method further comprises repeating steps (A) and (B) for different strips of glass ribbon exhibiting viscous action.

In a particular embodiment of the first aspect of the invention, in step (A), the thickness of each of the one or more regions is thicker than the target thickness, and in step (B) of each region of the one or more regions The thickness is reduced.

In a particular embodiment of the first aspect of the invention, step (B) comprises positioning the radiant heater adjacent to the strip and operating the radiant heater to direct radiant heat to one or more regions.

In a particular embodiment of the first aspect of the invention, in step (B), the radiant heater comprises an array of radiant heating elements, wherein step (B) comprises: It further comprises the step of polymerizing.

In a particular embodiment of the first aspect of the invention, in step (D), the radiant heating member is linear and inclined with respect to the conveying direction of the glass ribbon.

In a particular embodiment of the first aspect of the invention, in step (B), the radiant heater has a non-linear shape to maximize the radiation view factor between the radiant heater and one or more regions.

In a particular embodiment of the first aspect of the invention, the method further comprises (E) combining the separate stream of molten glass in the wedge-shaped root of the forming member to form the glass ribbon.

In a particular embodiment of the first aspect of the invention, in step (B), the radiant heater is located in the vicinity of the wedge-shaped route.

In a particular embodiment of the first aspect of the invention, in step (B), the radiant heater is an infrared heater.

According to a second aspect of the invention, a system for controlling the thickness profile of a glass ribbon is presented. The system includes a shaping member and a radiant heater for shaping a glass ribbon, the shaping member having a wedge-shaped route in which a separate stream of molten glass is joined to form the glass ribbon and the radiant heater has a viscous action. And to selectively apply radiant heat to a selected area of the glass ribbon representing the thickness and thickness outside the target thickness.

In a particular embodiment of the second aspect of the invention, the radiant heater is located near the wedge-shaped route.

According to a third aspect of the invention, a glass sheet manufacturing method is:

(i) providing a glass ribbon having a width formed by two both edges at a temperature at which the glass exhibits viscoelastic action;

(Ii) moving the glass ribbon while the glass exhibits a viscoelastic action; And

(Iii) heating the glass ribbon with the array of heater elements while the power of the heater element can be adjusted separately.

In a particular embodiment of the third aspect of the invention, step (i) comprises fusion molding the glass ribbon from the glass melt using an isopipe.

In a particular embodiment of the third aspect of the invention, in step (iii), the heater element is arranged to have an overlapping field of view.

In a particular embodiment of the third aspect of the invention, in step (iii), the heater member heats the ribbon differently from one edge to another across the width of the ribbon.

In a particular embodiment of the third aspect of the invention, step (iii) is:

(Iii-1) determining a change in thickness of the ribbon within the width;

(Vi-2) heating the ribbon differently within the width in accordance with the change in thickness such that the ribbon is drawn to a substantially constant thickness.

In a particular embodiment of the third aspect of the invention, in step (iii-2), the heater member further heats the area of the ribbon within the maximum thickness width rather than the minimum thickness area.

In a particular embodiment of the third aspect of the invention, in step (iii), the heater array is necessarily a linear array.

In a particular embodiment of the third aspect of the invention, in step (iii), the array of heater elements may apply heat to the full width of the glass ribbon.

In a particular embodiment of the third aspect of the invention, in step (iii), the heater member applies heat by irradiation of an infrared beam.

In a particular embodiment of the third aspect of the invention, step (i) comprises shaping the glass ribbon from the glass melt using an isopipe, wherein in step (iii) the heater member is routed to the isopipe. Is located nearby.

In a particular embodiment of the third aspect of the invention, in step (iii), the heater member is positioned to apply heat to the glass ribbon before the glass ribbon reaches the root of the isopipe.

In a particular embodiment of the third aspect of the invention, in step (iii), an array of heater elements is positioned on each side of the isopipe such that two glass ribbons on the two sides of the isopipe form a single glass. Heated separately before joining at the root to form a ribbon.

In a particular embodiment of the third aspect of the invention, in step (iii), an array of heater elements is positioned to apply heat to the glass ribbon under the root of the isopipe.

In a particular embodiment of the third aspect of the invention, in step (iii), an array of heater elements is positioned on each side of the isopipe to heat each side of the glass ribbon under the root of the isopipe. do.

Advantages and features of the present invention will become apparent from the description set forth below and the appended claims.

Description of the drawings of the accompanying drawings is described. BRIEF DESCRIPTION OF THE DRAWINGS The drawings of the present invention are schematically illustrated in order to facilitate a clear understanding of the present invention, and the accumulation and time points may be slightly exaggerated.

1 is a schematic diagram of a system for forming a thickness controlled glass ribbon.
2 is a side view of the system of FIG. 1.
3 is a cross-sectional view of the system of FIG. 2 along line 3-3.
4 is a view of a radiant heater with an array of radiant heating elements.
FIG. 5 is a view of a radiant heater having a controller for selectively operating the radiant heating element and an array of radiant heating elements arranged to remove the four sections.
6 is a cross-sectional view of the system of FIG. 5 showing an overlapping radiation beam.
7 shows a non-linear radiant heating member.

The invention has been described in detail with reference to the accompanying drawings. In this detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may not be described only by these specific details. In many instances, well known features and / or process steps have been described in detail to clarify the invention. Moreover, the same or similar reference numbers are used to indicate the same or similar components.

1 shows a glass ribbon 113 forming system and process with controlled thickness. The down draw molded member 101 of known construction, as shown in US Pat. Nos. 1,829,641 and 3,338,696, has converging surfaces 103 and 105 that terminate at the wedge-shaped root 107. The glass ribbon 113 commences with two streams 109, 111 of molten glass flowing down the converging surfaces 103, 105 of the forming member 101 and coalescing in the wedge-shaped root 107 to form a glass sheet. do. Molten glass 115 is transferred to the channel 117 of the forming member 101 and the molten glass 115 is transferred to the channel 117 in a known manner as described in US Pat. Nos. 1,829,641 and 3,338,696. ) Can be overflowed to form streams 109 and 111 of molten glass. The glass ribbon 113 is drawn out of the wedge-shaped root 107 into a sheet-shape. As the glass ribbon 113 is drawn, the glass ribbon 113 is cooled to change the glass from the viscous state to the 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. Uneven cooling in the viscous state results in uncontrolled thickness (eg, non-constant) in the elastic state. The process of FIG. 1 uses the reduction of heat loss from selected areas of the glass ribbon 113 to modify the cooling pattern of the glass ribbon 113 and to control the thickness of the glass ribbon 113 as described below. do.

In FIG. 1, a radiant heater 119 is provided adjacent the surface 121 of the glass ribbon 113. Radiant heater 119 acts radiant heat, indicated by line 123, on the selected area of glass ribbon 113. Criteria for selecting a region to which radiant heat is applied are described below. Radiant heat 123 moves with the glass ribbon 113 as the glass ribbon 113 is drawn from the wedge-shaped route 107, as indicated by the cross-hatched region 125. An imprint of radiant heat on the glass ribbon 113 determines the width 127 of the heated region 125. The spacing between the radiant heater 119 and the surface 121 and the appearance and output of the radiant heater 119 are appropriately selected to transfer the required amount of radiant heat to the surface 121. In FIG. 1, the radiant heater 119 is positioned where radiant heater 119 can exert radiant heat on the glass ribbon 113 on the wedge-shaped root 107. As an alternative arrangement, the radiant heater 119 may be located below the wedge-shaped route 107 or where it may exert radiant heat on the glass ribbon 113 at the wedge-shaped route 107. In general, the radiant heater 119 will be positioned where radiant heat acts on the area of the glass ribbon 113 exhibiting viscous action. In general, the area of the glass ribbon 113 exhibiting viscous action may be near the wedge-shaped root 107. A second radiant heater (not shown separately) may be provided on the opposite side of the glass ribbon 113 and may be used in the same manner to act on the glass ribbon 113 with radiant heat with the first radiant heater 119.

In order to control the thickness of the glass ribbon 113, a strip of glass ribbon (taken along the width of the glass ribbon 113) is selected. Typically, this strip of glass ribbon 113 may be part of the glass ribbon 113 adjacent to the radiant heater 119 at any given time during the forming process of the glass ribbon 113. To illustrate, FIG. 2 is a side view of the system of FIG. 1. In FIG. 2, strip 201 is shown in dashed lines, and radiant heater 119 is positioned opposite strip 201. 3 is a cross-sectional view of the system of FIG. 2 taken along strip 201. For strip 201, there is an out of thickness region 301 having a thickness that is outside the target thickness for the strip 201 or outside the standard thickness. Typically, region 301 is said to be "outside" because it has a thickness that is thicker than the target or standard thickness for the strip. Strip 201 may or may not have one or more such out of regions in general. The process of controlling the thickness of the glass ribbon 113 includes finding any out of the area on the strip 201. Finding out-of-area may include valid measurements on strip 201 or may be based on historical data obtained using a particular set of process setups and parameters.

Once the out-of-area is found on the strip 201, the radiant heater 119 is controlled to act on the out-of-area radiant heat. In the embodiment shown in FIG. 3, the radiant heater 119 may apply radiant heat to the out of zone 301, as indicated by the cross section 303. Radiant heat transferred to the off-area 301 will heat up the area 301. This reduces the viscosity in the off region 301 and reduces the thickness of the off region 301. The thickness may be reduced so that the modified out of region 301 thickness matches the target thickness or standard thickness of the strip 201. Typically, such heating results in an altered temperature distribution across strip 201, for example, the altered temperature distribution may be more constant than before region 301 is heated with radiant heater 119. This altered or more constant temperature distribution will move with the strip 201 along the direction of movement of the glass ribbon 113. Thereafter, another strip of glass ribbon 113 will be adjacent to the radiant heater 119. The process described above may be repeated for any one of these strips and for several future strips adjacent to the radiant heater 119 to locate the out-of-area and act on the out-of-area. However, this configuration does not mean that the radiant heater 119 needs to be stationary. The radiant heater 119 may be repositioned as needed to heat-treat various portions of the glass ribbon 113 having these off regions if these off regions exhibit viscous action.

1 through 3, chimneys on the surface of the glass ribbon 113 due to leakage of fluid to the draw, by using "direct" radiant heat to control the thickness of the glass ribbon 113 as described above. The chimney effect can be avoided because the fluid is not used to control the thickness of the glass ribbon 113. The expression “directly” means that heat exchange between the radiant heater 119 and the glass ribbon 113 is not impeded by the structure, such as the front wall used in the system described in the background. The radiant heater 119 can be positioned very close to the surface of the glass ribbon 113 to maximize heating efficiency. In addition, the appearance of the radiant heater 119 and the spacing of the radiant heater 119 from the glass ribbon 113 surface can be used to achieve a high-resolution clock for radiation. 1 to 3, the system described above is also well suited for automatic control as described below.

1 to 3, the radiant heater 119 generates electromagnetic radiation at a wavelength compatible with the absorption characteristics of the glass ribbon 113, so that radiant heat can be absorbed by the glass to affect viscosity reduction. have. Typically, radiant heater 119 may be an infrared radiant heater. The radiant heater 119 may comprise a single radiant heating element or may comprise an array of radiant heating elements. The radiant heating member may be made of a refractory metal such as Pt, Pt alloy, tungsten, MoSi ₂ or the like, or a ceramic material such as SiC. The heating member may take the form of a filament wire (eg tungsten wire) or a radiator plate (eg ceramic plate). Typically, a radiant heating member made of filament wire may include a wire in a loop that is wound to increase the surface area that generates radiant heat. The radiant heating member may be disposed in a transparent enclosure, such as a quartz enclosure. The enclosure may be coated with a reflective material to increase the amount of radiant heat transferred to the glass ribbon 113. The radiant heater 119 may be an electric radiant heater or an induction radiant heater. The radiant heater 119 may or may not extend across the width of the glass ribbon 113 (No. 203 in FIG. 2). A plurality of radiant heaters 119 may be provided across the width of the glass ribbon 113 (abstract 203 in FIG. 2) and be operated to act on radiant heat to a number of out of the areas.

4 shows a radiant heater 119 including an array of radiant heating elements 401. The radiation heating member 401 is a linear radiation heating member. These heating elements are spaced apart and aligned with the direction of movement of the glass ribbon 113, as indicated by arrow 403 (only the relative portion of the glass ribbon 113 is briefly shown in FIG. 4). Because of the spacing between the radiant heating members 401 and the alignment of the radiant heating members 401 and the movement direction 403 of the glass ribbon 113, the gap 404 between the radiant heating members 401 which does not receive direct radiant heat ( There is a portion of the glass ribbon). These parts are referred to below as "dead zones". In order to eliminate the quadrilateral, the radiant heating member 401 may be arranged such that the field of view of the heating member (or imprint of radiant heat on the glass ribbon 113) overlaps. 5 shows how this configuration is done. In FIG. 5, the four radiant heating elements 501, 503, 505, 507 are spaced apart and inclined with respect to the direction of movement of the glass ribbon 113, indicated by arrow 508, so that the radiant beam made of one radiant heating element The radiation beams created by the adjacent radiation heating elements overlap, for example, the radiation beams created by the radiation heating elements 501 will overlap the radiation beams produced by the radiation heating elements 503 and the like. 6 shows overlapping radiation beams 601, 603, 605, 607 corresponding to radiant heating elements 501, 503, 505, 507. It will be appreciated that the social density of the radiation beam was used only as a visual tool to distinguish one radiation beam from the side radiation beam.

An array of radiant heating elements can be connected with the controller. This configuration is shown in FIG. 5 in which the radiant heating elements 501, 503, 505, 507 are connected (or in communication) with the controller 509. The controller 509 can be operated to individually turn on or turn off the radiant heating elements 501, 503, 505, 507. The controller 509 may receive the outside input, as indicated by the reference number 511. An example outer input 511 may be a thickness profile or a temperature profile across a strip of glass ribbon 113. The controller 509 uses the information to determine whether the radiant heating elements 501, 503, 505, 507 are to be turned on and off, to achieve a target thickness across the strip of glass ribbon 113 or to distribute the temperature. Can be achieved. This configuration is based on the glass ribbon 113 based on the thickness or temperature profile at which the thickness or temperature profile is measured at a particular position across the glass ribbon 113 and the radiant heating elements 501, 503, 505, 507 are measured. It will be appreciated that it may be an ongoing process that is controlled to transfer heat to a given strip of. Additional or thermal sensors can be used to measure the thickness or temperature profile, respectively. The glass ribbon 113 can also be visually inspected and the turn on or turn off of the radiant heating elements 501, 503, 505, 507 can be determined. Information obtained by visual inspection can be used to operate the controller 509.

It will be appreciated that the radiant heater 119 shown in FIG. 1 includes a single radiant heating element or an array of radiant heating elements. Multiple radiant heaters 119 may be used as the system, or a single radiant heater 119 with an array of radiant heating elements may be used as the system. The radiant heater 119 may have a width spaced by the width of the glass ribbon 113 or may have a width smaller than the width of the glass ribbon 113. If an array of radiant heating elements is used, the controller can be used to individually control the radiant heating elements that operate at any time. A controller can also be used to adjust the output of the radiant heating element. For example, in FIGS. 4, 5 and 6, it will be appreciated that the radiant heating member is not limited to the linear radiant heating member as shown. Nonlinearly shaped radiant heating elements can be used to maximize or increase the radiant form factor. The radiation form factor is a fraction of thermal energy that leaves the surface of the first object and reaches the surface of the second object, determined entirely from geometric considerations. 7 shows an elliptical radiant heating member 701 and an arbitrary radiant heating member 703. The member 703 is indefinite and is intended to show how the invention produces a shape that takes the shape of a feature that particularly requires correction. For example, an “L” shaped member may be positioned such that the L-shaped vertical segment exhibits a concentrated heating effect for the wider, more diffused effect of the horizontal segment. The final conclusion may be the asymmetric effect on the glass. In general, the nonlinear shape can be selected based on the typical shape of the glass ribbon region to be heated by the radiant heater.

Although the present invention has been described in a limited number of embodiments, those skilled in the art will understand that various changes and modifications to the present invention can be made within the scope of the present invention. . Accordingly, the invention is limited only by the appended claims.

Claims (26)

As a thickness profile control method of a glass ribbon,
(A) for a selected strip of glass ribbon exhibiting viscous action, finding one or more regions on the strip having a thickness that is outside the target thickness for the strip; And
(B) acting to radiate heat to said at least one region of said strip to reduce the viscosity of the glass in at least one region. The method according to claim 1,
(C) further comprising repeating steps (A) and (B) for different strips of the glass ribbon exhibiting viscous action. The method according to claim 1,
In step (A), the thickness of each of the one or more areas is thicker than a target thickness, and in step (B) the thickness of each of the one or more areas is reduced. How to control the thickness profile of the ribbon. The method according to claim 3,
And said step (B) comprises positioning a radiant heater adjacent said strip and operating said radiant heater to direct radiant heat to said one or more regions. The method of claim 4,
In step (B), the radiant heater comprises an array of radiant heating elements, and step (B) comprises:
(D) overlapping the field of view of adjacent radiant heater elements in said array. The method according to claim 5,
In the step (D), the radiant heating member is linear and inclined with respect to the moving direction of the glass ribbon. The method of claim 4,
The method of controlling the thickness profile of a glass ribbon of claim (B), wherein the radiant heater has a non-linear shape to maximize radiant form factor between the radiant heater and the one or more regions. The method of claim 4,
(E) combining the separate streams of molten glass in the wedge-shaped root of the forming member to form a glass ribbon. The method according to claim 8,
In the step (B), the radiant heater is located in the vicinity of the wedge-shaped root, the thickness profile control method of the glass ribbon. The method of claim 4,
The method of controlling the thickness profile of a glass ribbon according to step (B), wherein said radiant heater is an infrared heater. As a thickness profile control system of glass ribbon,
A forming member for forming the glass ribbon, the wedge-shaped route having a separate stream of molten glass joined to form the glass ribbon; And
And a radiant heater disposed to selectively radiate heat to a selected area of the glass ribbon that exhibits viscous action and to a thickness that is outside of a desired thickness. The method of claim 11,
And the radiant heater is positioned near the wedge-shaped route. As a glass sheet manufacturing method,
(i) providing a glass ribbon having a width formed by two opposite edges at a temperature at which the glass exhibits viscoelastic action;
(Ii) moving the glass ribbon wherein the glass exhibits a viscoelastic action; And
(Iii) heating the glass ribbon with an array of heater elements,
The power of the heater member is adjusted separately. The method according to claim 13,
Wherein step (i) comprises fusion molding the glass ribbon from the glass melt using an isopipe. 14. The method according to claim 13 or 14,
In the step (iii), the heater member is arranged to have an overlapping field of view. The method according to any one of claims 13 to 15,
In the step (iii), the heater member heats the ribbon differently across the width of the ribbon from one edge to the other edge. The method according to any one of claims 13 to 16,
Step (iii)
(Iii-1) determining a change in thickness of the ribbon within the width;
(Vi-2) heating the ribbon differently in width in accordance with the change in thickness such that the ribbon is drawn to a substantially constant thickness. 18. The method of claim 17,
In the step (iii-2), the heater member applies more heat to an area of the ribbon within a width having a maximum thickness than an area having a minimum thickness. The method according to any one of claims 13 to 18,
In the step (iii), the heater array is essentially a linear array. The method according to any one of claims 13 to 19,
In the step (iii), the array of heater elements is capable of applying heat to the entire width of the glass ribbon. The method according to any one of claims 13 to 20,
In the step (iii), the heater member applies heat by irradiating an infrared beam. The method according to any one of claims 13 to 21,
Said step (i) comprises shaping said glass ribbon from a glass melt using an isopipe, wherein in said step (iii) said heater member is located near the root of said isopipe. Method for manufacturing glass sheet. 23. The method of claim 22,
And wherein said heater member is positioned such that said heater member heats said glass ribbon before said glass ribbon reaches said root of said isopipe. 24. The method of claim 23,
In said step (iii), each of said isopipes is arrayed so that two glass ribbons on two sides of said isopipe are heated separately before they are joined at said root to form a single glass ribbon. Glass sheet manufacturing method, characterized in that located on the side of. 23. The method of claim 22,
And wherein said array of heater elements is positioned to apply heat to said glass ribbon under said root of said isopipe. 23. The method of claim 22,
In the step (iii), the array of heater elements is located on each side of the isopipe to heat each side of the glass ribbon under the root of the isopipe. Manufacturing method.

Images