TW201332906A - Apparatus and method for removing edge portions from a continuously moving glass ribbon - Google Patents

Abstract

Disclosed is an apparatus and method for thinning a portion of a glass ribbon drawn from a forming body. The thinning is produced by directing a flow of heated gas from a heating nozzle at a predetermined position on the glass ribbon. As the glass ribbon descends from the forming body, the thinned portion gross lengthwise along the glass ribbon edge portions of the glass ribbon may be removed from the glass ribbon as the glass ribbon descends from the forming body by propagating a crack along the thinned portion.

Description

Apparatus and method for removing edge portions from continuously moving glass ribbon

The present invention relates to an apparatus and method for producing a partially thinned continuous moving glass ribbon, and more particularly to the use of an edge portion for removing a glass ribbon by extending a crack along the thinned portion. Equipment and methods.

High-yield, continuous glass is known for use in display systems such as liquid crystal displays or organic light-emitting diode display technology, as components of optoelectronic devices, or as cover sheets for various types of covers for handheld devices and televisions. The sheet manufacturing process (such as a float process or a melt down process) is produced, but in some specific cases it can be produced using a slit stretching process.

The glass ribbon produced by the above process exhibits an increased thickness near the edge of the belt and is generally referred to as a "ball". It is generally observed that the bead thickness is 3 to 4 times the nominal thickness of the central portion of the glass ribbon. This ratio tends to increase when a very thin glass ribbon is produced, and when the central portion of the glass ribbon is considered to be on the order of 0.1 mm, the ratio may reach a value up to 10 times the thickness of the central portion of the glass ribbon.

The presence of these beads may be desirable in earlier manufacturing processes where the glass ribbon is formed and stretched by viscous deformation by means of sheet stabilization, sheet width loss control, thickness control contribution, and the like. However, the effects of these beads on internal stresses and the shape of the sheets in subsequent processes may not be required and may be detrimental to the process and the final product under certain circumstances.

In order to achieve a low level of internal stress in the glass ribbon, the cooling rate must be carefully controlled during the molding process. Significant thickness differences between different regions of the strip can result in different cooling rates, resulting in a temperature gradient that reduces the ability to achieve low stress. This is the case in the bead region where a large thickness gradient causes large temperature and stress gradients.

In the production of very thin sheets, it is desirable to wind the glass ribbon on a reel instead of cutting into separate glass sheets to accommodate high stretching speeds. The presence of these thicker beads limits the ability to bend the sheet into a sufficiently small radius of curvature without causing crack propagation and product loss.

Disclosed herein is a method and apparatus for selectively removing a portion of a glass ribbon by applying localized heating to continuously remove the beads from a continuously moving glass ribbon.

For the melt down process, the most desirable location for maximizing the thinning of the ribbon is near the root of the shaped body. For the slit stretching process, the most desirable position is near the slit. Local modification of the glass viscosity is performed in the viscous region of the process using a local heat generator. When traveling in the downward direction, by heat exchange by radiation and convection, the thin section of the glass ribbon will develop thermomechanical stress induced by a thermal gradient, which can be used To extend the crack that initiates in the elastic region (usually under the pull rolls) and reach up to the top of the viscoelastic region, thus effectively separating the beads from the remainder of the glass sheet. Once the crack is initiated, this separation can be supported and controlled by adjusting the local viscosity near the root and adjusting the cooling rate in the thinned area below the stretch leaving the root. Adjusting the local viscosity near the root of the shaped body can be done using a forced air heated nozzle.

The heated nozzle contains a small heat generator that can be used to transfer energy to the glass near the root, primarily by convection, and to some extent by radiation. Heat transfer efficiency is achieved by high velocity hot air jet impingement on the glass surface, which provides a localized and adjustable viscosity gradient by controlling air flow, air velocity, air temperature, and air to glass flow direction.

Although crack initiation can occur spontaneously, it can be caused by, for example, local heating/cooling (eg, first CO ₂ laser followed by air jet or air/water mist) to promote a very high stress gradient or by damaging the glass surface (eg, Mechanically, the glass cutter is used, or a very local twist is applied by the pair of rolls, and the initiation is controlled at a predetermined position in the stretch.

Accordingly, disclosed herein is an apparatus for forming a glass ribbon, the apparatus comprising a shaped body and a heated nozzle, the shaped body comprising a converging forming surface joined at a bottom of the shaped body, the heated nozzle comprising a refractory tube And a heating element located around the refractory tube, the refractory tube comprising: a plurality of channels extending longitudinally between the first end and the second end of the refractory tube, wherein at least one of the plurality of channels and the gas flowing fluid Connected, the gas flow is directed through the at least one passage, the first end and the The bottom of the body is adjacent; the heating element is located around the refractory tube and is configured to heat the gas flow. Preferably, the refractory tube is located within the refractory sleeve, wherein the heating element is then positioned between the refractory tube and the refractory sleeve.

The apparatus can further include a cooling door positioned below the bottom of the molded body, and wherein the heated nozzle is positioned between the bottom of the molded body and the cooling door. The function of the cooling door is to adjust the thickness of the glass ribbon over the entire width of the glass ribbon by directing the cooling gas to a hot plate adjacent to the lowered glass ribbon.

Preferably, the heated nozzle is positioned to direct the heated gas flow to a portion of the glass ribbon, and the portion of the glass ribbon has a distance from the edge of the glass ribbon that is equal to or less than about 100 mm. For example, the heated nozzle can be positioned to direct the heated gas flow to a portion of the glass ribbon, and the portion of the glass ribbon has a distance from the edge of the glass ribbon that is equal to or less than about 50 mm. Preferably, the refractory tube is located within the insulated shield.

In another embodiment, a method of locally thinning a continuously moving glass ribbon is described, comprising the steps of flowing molten glass from a shaped body, the shaped body comprising a converging forming surface, the converging forming surfaces being bonded at a root, the molten glass Forming a continuously moving glass ribbon from which the continuously moving glass ribbon is drawn; directing a flow of heated gas from the heated nozzle to the glass ribbon, the heated gas striking the glass ribbon adjacent the root, the heating of the impact The gas produces a partially thinned portion of the glass ribbon that extends along the length of the glass ribbon; and the edge portion is separated from the glass ribbon by extending a crack along the thinned portion. The temperature of the heated gas is preferably in the range of from about 1450 ° C to about 1650 ° C. Preferably, by using a laser The thinned portion is heated, and then the thinned portion is cooled using a cooling fluid to extend the crack.

In some embodiments, the heated gas impinges on the glass ribbon between the edge director and the centerline of the glass ribbon. For example, the heated gas can impinge closer to the edge director and less near the centerline. Preferably, the heated gas impinges on the glass ribbon within about 100 mm from the edge of the glass ribbon, such as within about 50 mm from the edge of the glass ribbon. Preferably, the thinned portion comprises a tensile stress that is bound by a thickened portion that includes a compressive stress.

Additional features and advantages of the invention will be set forth in the <RTIgt; The invention, including the following embodiments, the scope of the claims, and the accompanying drawings, are to be understood as the invention.

It is to be understood that the foregoing general description and the embodiments of the present invention The drawings are included to provide a further understanding of the invention and constitute a part of this specification. The drawings illustrate various embodiments of the invention and, together,

10‧‧‧Fused glass manufacturing equipment

15‧‧‧Fusing furnace

20‧‧‧Refining containers

25‧‧‧Stirring container

30‧‧‧ Receiving container

35‧‧‧ downflow tube

40‧‧‧ entrance

45‧‧‧Forming body

50‧‧‧Mobile belt

55‧‧‧Connecting tube

60‧‧‧Connecting tube

65‧‧‧Connecting tube

70‧‧‧ batch materials

75‧‧‧ arrow

80‧‧‧Solid glass

90‧‧‧Open channel

95‧‧‧Molded surface

100‧‧‧ root

105‧‧‧Scoring/Dash

106‧‧‧Edge director

110‧‧‧ Puller

115‧‧‧Edge section

120‧‧‧balls

125‧‧‧Quality section

130‧‧‧dotted line

135‧‧‧ Shell

140‧‧‧heating elements

145‧‧‧ interior wall

150‧‧‧Cooling door

155‧‧‧Cooling nozzle

160‧‧‧ arrow

165‧‧‧ front board

170‧‧‧heating nozzle

180‧‧‧Refractory body

185‧‧‧ channel

190‧‧‧heating gas

195‧‧‧ first end

200‧‧‧ second end

205‧‧‧Fireproof sleeve

210‧‧‧ heating element

220‧‧‧ thermocouple components

225‧‧‧Insulation shield

226‧‧‧ edge

230‧‧‧ center line

235‧‧‧ Thinned area

236‧‧‧Local thickening

240‧‧‧Laser

245‧‧‧Cooling fluid

F‧‧‧ force

V‧‧‧ vector

1 is a schematic view of an exemplary molten glass manufacturing apparatus; and FIG. 2 is a front view of a molten glass forming body included in the apparatus of FIG. 1; Fig. 3 is a perspective view showing the edge director of the molded body shown in Fig. 2; Fig. 4 is a cross-sectional view showing the width of the glass ribbon (stretched from the molded body of Fig. 2); Fig. 5 is the second drawing FIG. 5 is a cross-sectional view of a molded body viewed from one end of the molded body, FIG. 5 is a view showing a configuration of a heating nozzle according to an embodiment of the present invention; and FIG. 6 is a cross-sectional side of the heated nozzle in the protected refractory sleeve and the heat shield. Figure 7 is a cross-sectional view of a portion of the glass ribbon of Figure 4, Figure 7 illustrates the effect of a heated nozzle adjacent the bead of the glass ribbon; and Figure 8 shows the molten glass per unit volume and shows the effect The force on the unit volume of molten glass; Figure 9 shows the strip thickness across the central portion of the ribbon; and Figure 10 shows the strip thickness near the glass ribbon when struck by the heated gas from the heated nozzle. .

In the following embodiments, the exemplary embodiments are set forth to provide a It will be apparent, however, to those skilled in the art that the present invention may be practiced in other embodiments that deviate from the specific details disclosed herein. In addition, descriptions of well-known devices, methods, and materials may be omitted to avoid obscuring the description of the invention. Finally, the same reference symbols refer to the same elements throughout the application.

1 and 2 illustrate an exemplary embodiment of a molten glass manufacturing apparatus 10 for molding a glass sheet, the molten glass manufacturing apparatus 10 including a melting furnace 15, a refining vessel 20, a stirring vessel 25, a receiving vessel 30, and a downflow The tube 35, the inlet 40, and the molded body 45 in which the thin continuous moving belt 50 of the molten glass molding material descends from the molded body 45. The glass manufacturing system 10 further includes various other containers or conduits for transporting the molten glass forming material, including the furnace to the refining vessel connecting pipe 55, the refining vessel to the agitating vessel connecting pipe 60, and the agitating vessel to the receiving vessel connecting pipe 65. While the melting furnace and the forming body are typically formed from a ceramic material, such as ceramic tiles containing alumina or zirconia, the various vessels and intervening conduits often contain an alloy of platinum or platinum, such as a platinum-rhodium alloy. Although the following description relates to an exemplary melt down process, such as the process illustrated in FIG. 1, the embodiments disclosed herein are equally applicable to other variations of the drop down glass fabrication process, such as a one-sided overflow process or slit. Stretching processes, which are well known to those skilled in the art.

According to the exemplary melting process of Fig. 1, the melting furnace 15 is equipped with a batch material 70 which, as indicated by arrow 75, melts the batch material 70 by a melting furnace to produce a glass forming material (hereinafter molten glass 80). The molten glass 80 is sent from the melting furnace 15 to the refining vessel 20 via the melting furnace to the refining vessel connection pipe 55. The molten glass is heated in the refining vessel 20 to a temperature higher than the temperature of the melting furnace, and then the polyvalent oxide material contained in the molten glass releases oxygen, and the oxygen rises through the molten glass. The high temperature oxygen release in this refining vessel 20 helps to remove small bubbles within the molten glass produced by the molten batch material.

Then, the molten glass enters the agitating vessel 25 from the refining vessel 20 via the refining vessel to the agitating vessel connecting pipe 60, wherein the rotary agitator mixes and both The molten glass is sized to ensure uniform consistency. The homogenized molten glass from the agitating vessel 25 then flows through the agitating vessel to the receiving vessel connecting pipe 65 and is collected in the receiving vessel 30. The molten glass from the receiving container 30 is conveyed to the molding main body 45 via the downflow pipe 35 and the inlet 40, and the molten glass is molded into the glass ribbon 50 by stretching the molten glass from the molding main body.

The shaped body 45 includes an open channel 90 on the upper surface of the shaped body and a pair of converging forming surfaces 95, as best seen in Figures 2 and 3, the pair of converging forming surfaces 95 converge on the shaped body Bottom or root 100. The molten glass supplied to the molded body flows into the open passage 90 formed on the upper surface of the molded body 45, and overflows from the wall of the open passage 90, thereby being separated into two separate molten glass streams which are concentrated on the shaped surface Flowing on. When the separated molten glass stream reaches the root, the separated molten glass stream is recombined (or fused) to form a glass ribbon 50 that is lowered from the root of the shaped body. As best seen in Figure 3, the edge director 106 positioned on the shaped body 45 functions to effectively extend the width of the root, thereby facilitating the expansion of the glass ribbon, or at least minimizing the effect of the glass ribbon. Narrowing. FIG. 3 is a perspective view showing a partially molded body 45 of the edge director 106. In operation, there are typically four edge directors, two edge directors facing each other at one end of the forming body, and another pair of opposing edge directors being positioned at opposite ends of the forming body.

As the glass ribbon is lowered from the root 100, the pull roll 110 contacts the viscous glass ribbon along the edge of the glass ribbon and assists in stretching the glass ribbon at a velocity vector V on a downward path, the velocity vector V including both direction and velocity. . The pull roller 110 includes opposing, counter-rotating rollers that grip the edge portions of the glass ribbon And stretch the glass strip down. Additional drive or non-drive rollers located above or below the pull rolls (not shown) may also contact the edges of the glass ribbon to assist in guiding the glass ribbon and maintaining the width of the glass ribbon against the naturally occurring surface tension that is maintained. The effect is to shorten the width of the glass ribbon in other ways.

Once the lowered glass ribbon has cooled through the glass transition temperature range and a portion of the glass ribbon has been converted from a viscous liquid to an elastic solid, a separate glass sheet can be produced from the glass ribbon. Producing a separate glass sheet from a continuous and continuously moving glass ribbon typically involves first scribing the entire width or partial width of the glass ribbon. Tensile stress can then be applied over the entire score (indicated by dashed line 105) to create a crack that extends through the thickness of the glass ribbon and the width of the entire ribbon. The score 105 can be formed by any existing method. For example, the score 105 can be created by contacting the glass ribbon with a score wheel, a scribe, or an abrasive member that creates a surface damage on the glass ribbon. The glass ribbon can be bent in a direction in which the scored side of the glass ribbon is in tension to apply the tensile stress throughout the score line. The tension then drives the crack formed in the score line through the thickness of the glass ribbon and the entire width of the glass ribbon.

In a pull-down process (such as a melt or slot drawing process), the result of the relatively free hanging band of the glass forming material is that surface tension and high flow density near the edge portion 115 of the glass ribbon may cause the glass ribbon to be in the belt. Thickening near the end edge, as illustrated in Figure 4. These thickened regions are commonly referred to as balls 120. Figure 4 is a cross-sectional illustration of the edge portion 115 of a glass ribbon (including balls 120) formed by a melt process (such as the melt process described above). Since the intent of the process is to form a high purity glass sheet, the high purity glass sheet has a clean surface and a substantially parallel major surface (substantially uniform) The thickness of the ball 120, which is present in the edge portion 115 of the glass ribbon, is detrimental to the commercial value of the glass sheet cut from the glass ribbon. Therefore, the beads are usually removed.

Although the current practice is to remove the glass from the continuously moving glass ribbon and then remove the beads from the glass, this approach has significant drawbacks. In particular, there is a disadvantage in that it is difficult to reliably score the glass ribbon over the entire width of the glass ribbon while maintaining a clean, straight break. The uneven thickness of the edge portion of the glass ribbon causes uncontrolled cracking of the glass, wherein the score line or, more often, the subsequent separated cracks may deviate from the predetermined path. To overcome this tendency, scoring is often performed on the inner quality portion 125 (between the dashed lines 130) of the glass ribbon without scoring the beads. The quality portion 125 is located between the edge portions 115 on either side of the glass ribbon and is typically a portion of the glass ribbon that is a marketable product. However, the energy required to extend the separation crack across the un-scored ball can cause large disturbances to the glass ribbon during the separation process, which can extend into the glass transition zone of the glass ribbon and cause undesirable defects on the glass ribbon. influences. For example, stress may be frozen in the glass ribbon to affect the final shape of the glass sheet.

Figure 5 illustrates an end cross-sectional view of an exemplary molded body 45 for a melt down process (such as the melt down process illustrated in Figure 1). According to Fig. 5, the molded body 45 is housed in the outer casing 135 which maintains a stable thermal environment around the molded body. Heating element 140 is used to control the temperature within housing 135. Heating element 140 can be, for example, a resistively heated metal coil or rod. The inner wall 145 diffuses the heat generated by the heating element 140 and assists in providing more uniform heating of the shaped body and the molten glass. The inner wall 145 may be formed of, for example, tantalum carbide. Since the glass ribbon is stretched from the molding main body 45 by the pulling roller 110, the thickness of the glass ribbon is thick. The degree (e.g., the thickness within the quality portion 125) is controlled by the cooling gate 150. The cooling door 150 is configured to be movable such that the cooling door can be retracted in a direction toward the glass ribbon or away from the glass ribbon. The cooling door extends across all or a significant portion of the ribbon width (i.e., in a direction perpendicular to the stretch vector V, the stretch vector V represents the direction and speed at which the ribbon is stretched).

Accommodating each of the cooling doors is a plurality of cooling nozzles 155 that supply cooling gas, typically air. Air may be cooled before being delivered to the cooling nozzle 155. Cooling gas exiting the cooling nozzle 155 (as indicated by arrow 160) is directed to the front plate 165 of each of the cooling doors. The front plate 165 may be formed of, for example, tantalum carbide. Local cooling can be obtained on the front panel of the cooling door so that a varying temperature distribution can be produced over the entire width of the front panel. The local cooling of the front panel affects the viscosity of the glass ribbon and thus the thickness of the glass ribbon directly adjacent to a particular portion of the front panel. Thus, the thickness of the glass ribbon across the width of the glass ribbon can be controlled by varying the temperature and/or flow of the cooling gas through the cooling nozzle 155. By directing the cooling gas to the plate between the cooling nozzle and the glass ribbon, the effect of the cooling nozzle on the overall stretch can be mitigated.

In accordance with various embodiments described herein, a plurality of heating nozzles 170 are positioned above the cooling door 150 and are configured to direct heated air to a particular portion of the continuously moving glass ribbon. The following description will be directed to one such heating nozzle 170, and it is understood that the description is equally applicable to the remaining heating nozzles 170.

As illustrated in FIG. 6, each heating nozzle 170 includes a refractory body 180 that includes a plurality of channels 185. A heated gas 190, such as air, is delivered to at least one of the plurality of channels 185 at a first end 195 of the refractory body 180 and exits the channel from the second end 200 of the refractory body 180. The second end 200 is located adjacent to the glass ribbon 50. The refractory body 180 can be positioned within the refractory sleeve 205 such that the refractory sleeve 205 substantially concentrically surrounds the refractory body 180. The refractory sleeve 205 can be made, for example, of alumina (Al ₂ O ₃ ).

A high temperature heating element 210 (eg, a wire coil) is disposed around the refractory body 180. For example, if the heating element 210 is a coil, the heating element 210 can be wrapped around the refractory body 180. Heating element 210 is preferably positioned between refractory body 180 and refractory sleeve 205. Heating element 210 can be formed, for example, from a platinum-containing wire or other suitable refractory metal. For example, the wire can be a platinum alloy such as platinum-ruthenium. The heating element 210 is supplied with a current to heat the heating element 210 and thereby heat the refractory body 180 with the heated gas 190 traveling within the at least one passage 185. For example, a single heated nozzle may require power equal to or greater than about 400 watts to adequately heat the heated gas flowing through the refractory body 180. The heating gas 190 flowing in the at least one passage 185 is preferably heated to a temperature equal to or greater than 1450 °C. For example, the heating gas can be heated to a temperature ranging from about 1450 ° C to about 1650 ° C, and the heating gas can be heated to a temperature ranging from about 1500 ° C to about 1650 ° C, and the heating gas can be heated to The temperature in the range from about 1550 ° C to about 1650 ° C, or the heated gas may be heated to a temperature in the range from about 1600 ° C to about 1650 ° C. In order to ensure adequate heating of the gas flow, at least one of the channels 185 should have a suitable internal diameter. For example, the inner diameter of at least one of the channels 185 can be equal to or greater than 1 millimeter (mm). Other passages of the refractory body 180 may include instruments or other means for measuring the temperature of the heated gas. For example, as illustrated in the embodiment of FIG. 6, other channels 185 housed within the refractory body 180 can include thermocouple elements 220. refractory The sleeve 205 can be located within a suitable insulating shroud 225 that is disposed about the refractory sleeve 205.

As best seen by Figures 2-3, the heating nozzle 170 is preferably located at or near the root 100 and inside the edge 226 of the glass ribbon 50 (e.g., between the edge 226 of the glass ribbon and the centerline 230). . For example, the heating nozzle 170 can be positioned vertically between the root 100 and the cooling door 150, and the heating nozzle 170 can be positioned laterally such that the heated gas ejected by the nozzle is directed to the edge portion 115 to be removed from the quality portion 125. position. Preferably, the position of the heated nozzle 170 is such that the heated gas 190 is directed to a position between the inner edge of the edge director 106 and the centerline 230 of the glass ribbon 50. The heated gas ejected from the heating nozzle 170 strikes the glass ribbon and locally reduces the viscosity of the glass, thereby causing local thinning of the glass ribbon. As the continuously moving glass ribbon continues to descend from the contoured body 45, the localized thinning forms a narrow, thinned region 235 that travels longitudinally along the length of the glass ribbon (see Figure 7).

Figure 8 shows the idealized infinitely wide-band glass cell volume at a vertical pull-down force F. In equilibrium, two sets of adjoint forces appear, each force equaling F/2: a set of forces perpendicular to the glass ribbon and thinning the glass ribbon The other group is in the plane of the glass and is balanced with the volume of the glass unit adjacent in the horizontal direction. The force described hereinafter is responsible for the reduction in the width of the glass ribbon because the edges of the glass ribbon cannot be in equilibrium due to the absence of directly adjacent glass volumes. With such a distribution of forces, the thinning of the glass occurs only in the vertical direction (the thickness variation due to stretching only in the vertical direction).

The change in the magnitude of the tensile force F is a function of viscosity, fluid density, and length reduction (in inverse proportion to the cooling rate and the stretching speed), and can be approximated by the following expression. Where η is the viscosity, Q is the fluid density, and L is the length reduction. For example, if a negative viscosity gradient is locally introduced using a heated nozzle 170 but away from the edge, a reduction in the tensile force F occurs, and thus the horizontal force component contained within the plane of the belt is reduced. In order to maintain the internal balance, horizontal glass flow occurs in the direction of adjacent glass volume units, inducing local thinning of the belt. However, the cost of forming the thinned regions 235 is a local thickening (236) of adjacent glass volume cells, as illustrated in FIG. The thickness response illustrated in Figure 7 represents what happens if, for example, the heated nozzle is directed toward the center of the glass ribbon.

On the other hand, if a negative viscosity gradient is introduced near the edge 226 of the glass ribbon, this horizontal flow will not cause local thickening, or at least reduce local thickening 236, as this will (at least in part) be slightly increased. The width of the glass ribbon is offset, as illustrated by Figure 10. This happens because the edge portion of the glass ribbon (where the beads are formed) is usually balanced in horizontal force by the shortening of the width of the glass ribbon. If the horizontal force component is reduced, the width of the glass ribbon is increased.

When localized thickness control is achieved near the bead using the heated nozzle 170, such as within about 100 mm of the edge 226 of the glass ribbon, the edge portion can then be separated from the glass ribbon. Thermomechanical stress induced by a thermal gradient can be used to extend the crack in the elastic region of the glass ribbon (usually under the tension roller) and up to the top of the viscoelastic region, effectively separating the edges from the rest of the ribbon. Part 115 with the ball. The crack extension terminates in the viscoelastic region of the thinned section of the glass ribbon because most of the crack extension energy will Absorbed by viscous shear. It will be appreciated that the position of the viscoelastic region of the thinned section of the glass ribbon is a function of local temperature and cooling rate and can be adjusted as required by the heating nozzle 170, which in turn controls the local thickness and localized glass temperature. A heater below the molded body can also be used to adjust the local cooling rate below the stretched length (e.g., along a lengthy glass ribbon). Additional specific heating and/or cooling may also be used below the forming body to precisely adjust the cooling rate.

If the crack extends beyond the track of the thinned region 235, it will be quite disadvantageous for the glass ribbon. The extension control is performed by controlling the stress gradient in the thinned section and the section adjacent to the thinned section. As noted above, this stress may be caused by the coefficient of thermal expansion of the glass ribbon and is primarily a function of the temperature gradient and the thickness of the ribbon.

There is a thick portion on both sides of the thinned section 235, the thinned section will be under tension, and the adjacent thickened section will be in compression. This will preferentially promote crack propagation in the center of the thinned section 235 where the extension energy is minimal.

Once the crack is initiated, the local viscosity modification near the root 100 can be adjusted in terms of viscosity distribution and size by using the heating nozzle 170, and the longitudinal stretching of the thinned region can be adjusted by a function of the distance from the root. The lower cooling rate, while supporting and controlling the separation of the edge portion 115 from the glass ribbon 50 (i.e., from the quality portion 125). That is, the local viscosity of the glass ribbon can be controlled by controlling the temperature of the air leaving the heating nozzle 170.

It is also desirable to ensure that the separated edge portion 115 does not contact adjacent glass ribbons when the ribbon is lowered to the pull rolls and below, such contact can damage the quality region 125. This can be done, for example, by using a pull roller directly above, deviating from the glass An additional roller of a few centimeters of the ribbon is used to ensure that the separated beads leave the plane of the glass ribbon.

Although crack initiation can occur spontaneously, it is preferred that the crack be initiated at a predetermined location in the stretch, for example, by localized heating and/or cooling. For example, the thinning section 235 can be heated using a laser 240 (such as a CO ₂ laser) and then cooled by the use of a cooling fluid 245 (eg, air jet or air/water spray) to cause very high stress gradients (see Figure 2). Alternatively, the crack can be initiated by mechanically damaging the glass surface using a glass cutter or applying local distortion by a pair of rolls.

Various modifications and alterations of the present invention will be apparent to those skilled in the art without departing from the scope of the invention. Therefore, it is intended that the present invention cover the modifications and modifications

45‧‧‧Forming body

90‧‧‧Open channel

95‧‧‧Molded surface

100‧‧‧ root

106‧‧‧Edge director

170‧‧‧heating nozzle

195‧‧‧ first end

200‧‧‧ second end

Claims (10)

An apparatus for molding a glass ribbon, comprising: a molding body comprising a converging molding surface, the converging molding surface being combined at a bottom of one of the molding main bodies; a heating nozzle comprising: a refractory tube, the refractory The tube includes a plurality of channels extending longitudinally between the first end and the second end of the refractory tube, wherein at least one of the plurality of channels is fluidly coupled to a gas flow, the gas flow being directed Passing through the at least one passage, the first end is adjacent to the bottom of the molded body; and a heating element, the heating element is located around the refractory tube, the heating element is configured to heat the gas flow. The apparatus of claim 1 wherein the refractory tube is located within a refractory sleeve and the heating element is positioned between the refractory tube and the refractory sleeve. The apparatus of claim 1, wherein the apparatus comprises a cooling door located below the bottom of the forming body, and wherein the heating nozzle is located between the bottom of the forming body and the cooling door. The apparatus of claim 1, wherein the heating nozzle is positioned to direct the heated gas flow to a portion of the glass ribbon, and the portion of the glass ribbon has a distance from one of the edges of the glass ribbon that is equal to or less than about 100 mm . A method of locally thinning a continuously moving glass ribbon, comprising the steps of: Flowing from a molded body to a molten glass, the molded body comprising a converging forming surface joined at one portion, the molten glass forming a continuously moving glass ribbon, the continuously moving glass ribbon being pulled from the root Directing a heated gas stream from a heated nozzle to the glass ribbon, the heated gas impinging on the glass ribbon adjacent the root, the impinging heated gas producing a partially thinned portion of the glass ribbon, the partially thinned portion Extending along a length of the glass ribbon; separating an edge portion from the glass ribbon by extending a crack along the thinned portion. The method of claim 5, wherein the temperature of one of the heated gases is in a range from about 1450 ° C to about 1650 ° C. The method of claim 5, wherein the heated gas strikes between an edge director and a centerline of the glass ribbon. The method of claim 7, wherein the heated gas can impinge closer to the edge director and less near the centerline. The method of claim 5, wherein the heated gas impinges on the glass ribbon within about 100 mm from an edge of the glass ribbon. The method of claim 5, wherein the thinned portion comprises a stretch The tensile stress is bound by a thickened portion containing compressive stress.