WO2018132348A1

WO2018132348A1 - Pulling roll, apparatus and method for drawing glass ribbon

Info

Publication number: WO2018132348A1
Application number: PCT/US2018/012887
Authority: WO
Inventors: Ji-Wan BAEK; Kyung-Seok CHAE; Duck Kyo SEO; Ho-Jin SONG; Moo Seop SONG
Original assignee: Corning Incorporated
Priority date: 2017-01-12
Filing date: 2018-01-09
Publication date: 2018-07-19
Also published as: KR20180083151A; KR101951440B1; JP2020504071A; CN110612273A; TW201829328A

Abstract

A pulling roll for drawing a glass ribbon is disclosed. The pulling roll comprises a roll body comprising a central passage extending in the longitudinally therethrough, a shaft extending through the central passage and spaced apart from the body, a first flange movably positioned on the shaft, the first flange movable in a longitudinal direction of the shaft, and a spring configured to push the first flange in the longitudinal direction of the shaft.

Description

PULLING ROLL, APPARATUS AND METHOD FOR DRAWING GLASS RIBBON

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Korean Patent Application Serial No. 10-2017-0005315 filed on January 12, 2017 the contents of which are relied upon and incorporated herein by reference in their entirety as if fully set forth below.

FIELD

[0002] The present disclosure relates to a pulling roll, an apparatus and a method for drawing a glass ribbon.

BACKGROUND

[0003] In a glass sheet manufacturing process, a pulling roll is used to draw a glass ribbon to a desired final thickness. For example, the pulling roll is positioned below a tip or root of a fusion pipe to draw a glass ribbon, thereby controlling the speed of the glass ribbon leaving the fusion pipe and thus determining the final thickness of the glass ribbon.

[0004] A conventional pulling roll comprises a plurality of compressed ceramic discs that are stacked in a longitudinal direction of a shaft. The discs are locked in place and maintained under compression by collars on the shaft. The plurality of discs are components for contacting and drawing a glass ribbon and made of a ceramic composite (typically including ceramic fibers, mica, and clay).

[0005] However, such ceramic discs are susceptible to thermal shock and thus prone to releasing an excessive number of particles when they contact the glass ribbon at high temperature. These particles may attach to a surface of the glass ribbon to cause a surface defect known as an onclusion. In particular, when sheet glass is manufactured as a substrate for a flat panel display, the sheet glass should have no onclusions. That is because each onclusion becomes a defect area (for example, one or more defective pixels) of the final product (e.g., display panel). Accordingly, a pulling roll that minimizes or even prevents the formation of onclusions is needed in the art.

SUMMARY

[0006] The present disclosure provides a pulling roll, an apparatus and a method for drawing a glass ribbon that can minimize or prevent the formation of onclusions. For example, the pulling roll can be made of shock-resistant materials, thereby further preventing onclusions from forming.

[0007] In one embodiment, a pulling roll for drawing a glass ribbon is described wherein the pulling roll comprises a roll body comprising a central passage extending longitudinally therethrough, a shaft extending through the central passage and spaced apart from the roll body, a first flange movably positioned on the shaft, the first flange movable in a longitudinal direction of the shaft, and a spring configured to push the first flange in the longitudinal direction of the shaft. The spring is a coil spring positioned inside or outside the shaft. The coil spring positioned outside the shaft is extendable while surrounding at least a portion of the shaft. The roll body is one piece and comprises a fused silica material. The pulling roll can be a full length pulling roll or a stub pulling roll.

[0008] According to embodiments described herein, the first flange may further comprise a sleeve slidably engaged with the shaft and a cap extending outward from the sleeve. The cap contacts the roll body so that the first flange supports the roll body. The roll body and the cap may comprise a convex portion and a concave portion which receives the convex portion. The convex portion and the concave portion comprise complementary inclined surfaces that contact each other.

[0009] In some embodiments, the pulling roll may further comprise a rod installed inside the shaft and engaged with the spring, and a pin coupling the first flange to the rod, the shaft including at least one slot extending in the longitudinal direction of the shaft within which the pin is movable in the longitudinal direction of the shaft. The pulling roll further comprises a second flange fixed on the shaft, wherein the roll body is positioned between the first flange and the second flange.

[0010] In another embodiment, an apparatus for drawing a glass ribbon is disclosed. The glass ribbon drawing apparatus comprises at least a pair of first pulling rolls, and at least a pair of second pulling rolls positioned downstream of the pair of first pulling rolls in a draw direction along a pulling path, wherein the first pulling roll is the above described full length pulling roll and the second pulling roll is the above described stub pulling roll.

[0011] In yet another embodiment, a method for drawing a glass ribbon is described. The glass ribbon drawing method comprises drawing the glass ribbon with at least a pair of pulling rolls. The pulling rolls include a shaft, a roll body rotatable with the shaft, a movable flange positioned on the shaft and supporting the roll body, and a spring installed with the shaft and applying a force against the movable flange in a longitudinal direction of the shaft, wherein the roll body comprises a fused silica material and is spaced apart from the shaft. The drawing step comprises moving the movable flange in the longitudinal direction of the shaft relative to the shaft by means of the spring, so that the movable flange maintains the support of the roll body while drawing the glass ribbon.

BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1 schematically shows a glass manufacturing apparatus, which forms a glass ribbon from molten glass;

[0013] Fig. 2 schematically shows a glass ribbon drawing apparatus according to one embodiment;

[0014] Fig. 3 is a cross-sectional view showing an example where a glass ribbon is drawn by a pulling roll in the glass ribbon drawing apparatus shown in Fig. 2;

[0015] Fig. 4 is a plan view showing a pulling roll according to a first embodiment;

[0016] Fig. 5 is a cross-sectional view taken along a line VI -VI in Fig. 4;

[0017] Fig. 6 is an enlarged view of a portion A in Fig. 5;

[0018] Fig. 7 is a plan view showing a pulling roll according to a second embodiment; [0019] Fig. 8 is a cross-sectional view taken along a line VH-VH in Fig. 7;

[0020] Fig. 9 is an enlarged view of a portion B in Fig. 8;

[0021] Fig. 10 is a plan view showing a pulling roll according to a third embodiment, in which a coil spring is installed inside a shaft;

[0022] Fig. 11 is a plan view showing a pulling roll according to a fourth embodiment;

[0023] Fig. 12 is a plan view showing a pulling roll according to a fifth embodiment;

[0024] Fig. 13 is a cross-sectional view taken along a line XII- XII in Fig. 12;

[0025] Fig. 14a schematically shows a part of a pulling roll according to a sixth embodiment, which is not thermally expanded at a room temperature; and

[0026] Fig. 14b schematically shows a part of the pulling roll according to the sixth

embodiment, which is thermally expanded at a high temperature.

DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0028] Fig. 1 schematically shows a glass manufacturing apparatus according to an embodiment for forming glass ribbons from molten glass. Referring to Fig. 1, a glass manufacturing apparatus lOOincludes a melting vessel 101, a fining vessel 103, a mixing vessel 104, a delivery vessel 108, and a fusion draw machine (FDM) 120. Glass batch materials are introduced into the melting vessel 101 as indicated by arrow 102. The batch materials are melted in the melting vessel 101 to form molten glass 106. The fining vessel 103 has a high temperature processing area that receives the molten glass 106 from the melting vessel 101, and in the fining vessel 103, bubbles are removed from the molten glass 106. The fining vessel 103 is in fluid

communication with the mixing vessel 104 by a connecting tube 105. That is, molten glass 106 flows from the fining vessel 103 to the mixing vessel 104 through the connecting tube 105. The mixing vessel 104 stirs the molten glass 106 and is, in turn, in fluid communication with the delivery vessel 108 by a connecting tube 107 such that molten glass flows from the mixing vessel 104 to the delivery vessel 108 through the connecting tube 107. [0029] The delivery vessel 108 supplies the molten glass 106 through a downcomer 109 into the FDM 120. The FDM 120 comprises an enclosure 122 in which an inlet 110, a forming vessel 111 and a glass ribbon drawing apparatus 150 according to one embodiment are positioned. As shown in Fig. 1, the molten glass 106 flows from the downcomer 109 into the inlet 110 to thereby lead to the forming vessel 111. The forming vessel 111 includes an opening 112 that receive the molten glass 106 which flows into a trough 113. The molten glass 106 overflows the trough 113 and runs down two converging sides 114a, 114b as separate flows of molten glass. The separate flows fuse together along a bottom edge, or root 116, where the two sides 114a, 114b meet. The converged molten glass 106 is then drawn in a draw direction 151 by the glass ribbon drawing apparatus 150 to form a continuous glass ribbon 148. The glass ribbon drawing apparatus 150 comprises at least a pair of pulling rolls and an actuator for rotating and driving the pulling rolls.

[0030] Fig. 2 schematically shows an exemplary glass ribbon drawing apparatus (150), and Fig. 3 illustrates a glass ribbon drawn by the pulling roll in the glass ribbon drawing apparatus 150. Referring to Figs. 2 and 3, the glass ribbon drawing apparatus (150) comprises a plurality of pairs of pulling rolls for drawing a glass ribbon, the pairs of pulling rolls positioned along a pulling path (that is, along the draw direction (151), which is a direction in which the glass ribbon is drawn). Each pair of pulling rolls comprises two pulling rolls, wherein the glass ribbon 148 is drawn therebetween. Each pulling roll of each pair of pulling rolls contacts a first major surface of the glass ribbon 148 and a second major surface opposite the first major surface in a thickness direction of the glass ribbon 148, respectively, and the glass ribbon 148 is drawn by a rotation of the pulling rolls. In some embodiments, the glass ribbon drawing apparatus 150 comprises a pair of pulling rolls 161, which comprise two opposing full length pulling rolls 200, and a plurality of pairs (e.g., 162, 163, 164, 165, 166, 167) of pulling rolls, which comprise two opposing cantilevered stub pulling rolls 600, respectively. The full length pulling rolls 200 extend over a full width of the glass ribbon 148, and the stub pulling rolls 400 extend over only a part of the full width of the glass ribbon 148.

[0031] As shown in Figs. 2 and 3, the full length pulling roll 200 is positioned upstream of the stub pulling roll 600 and temporarily contacts the glass ribbon 148 over most of the full width of the glass ribbon to thereby draw the glass ribbon 148 and form the glass ribbon 148 during an initial stage of the drawing process. The stub pulling rolls 600 are positioned downstream from the full length pulling rolls 200 in the draw direction 151, and contact an edge of the glass ribbon 148 to draw the glass ribbon 148 in the draw direction 151. The speed at which the glass ribbon is drawn 148 is controlled by controlling an angular speed of each stub pulling roll 600 so that the final thickness of the glass ribbon 148 can be obtained.

[0032] Figs. 4 to 9 show embodiments of the above described full length pulling roll 200, and Figs. 10 to 13 show embodiments of the above described stub pulling roll 600. Features of the pulling rolls disclosed herein can be applied to any of the full length pulling roll and the stub pulling roll.

[0033] Figs. 4 to 6 show an exemplary full length pulling roll 200 according to a first embodiment. Fig. 4 is a plan view of the pulling roll, Fig. 5 is a cross-sectional view of the pulling roll of FIG. 4 taken along a line VI-VI, and Fig. 6 is an enlarged view of a portion A shown in Fig. 5. As shown in Figs. 4 and 5, the pulling roll 200 according to the first embodiment comprises a shaft 210, a roll body 220, a fixing flange 230, a movable flange 240, and a coil spring 250.

[0034] The shaft 210 comprises an approximately cylindrical shape and extends in a longitudinal direction of the shaft 210 (that is, an axial direction of the shaft 210). The roll body 220 is a portion of the pulling roll, which contacts the glass ribbon 148. The roll body 220 comprises an approximately cylindrical shape and defines a central passage 222 extending therethrough between a first end and an opposing second end of the roll body in a longitudinal direction of the roll body. A diameter Dl of the central passage 222 is greater than the outer diameter D2 of the shaft 210. That is, there is a predetermined gap Gl between the roll body 220 and the shaft 210.

[0035] The shaft 210 is inserted into the central passage 222 of the roll body 220 and the roll body 220 is installed on the shaft 210 by the fixing flange 230 and the movable flange 240, which will be explained below.

[0036] The roll body 220 of the pulling roll 200 according to the first embodiment may be made of fused silica, a non-crystalline form of silicon dioxide. Since fused silica has a coefficient of thermal expansion (CTE) of nearly zero (for example, 5.5 ^χ 10^" m/^°C at room temperature), fused silica is resistant to thermal shock. Fused silica also exhibits a very high heat-resistance. Thus, since the roll body 220 is made of fused silica, the pulling roll 200 can significantly reduce particle generation and release by thermal shock.

[0037] A conventional pulling roll structure is not suitable for material having a low coefficient of thermal expansion such as fused silica. For example, in a conventional pulling roll ceramic discs are compressed and fixed on the shaft by collars. The collars are fixed on the shaft.

They move together with the shaft if the shaft is thermally expanded.

[0038] Thus, if the shaft is thermally expanded at a high temperature, such as the temperature to which it is exposed during the operation of the pulling roll, the ceramic discs not only thermally expand, but because the collars move as the shaft also expands, compression force on the ceramic discs is reduced, causing the ceramic discs to further expand. Accordingly, the ceramic discs are not removed from the shaft, even though the fixed collars move due to the thermal expansion of the shaft. However, when the coefficient of thermal expansion of the roll body 220 is very low, such as in the embodiments disclosed herein, if the roll body 220 is fixed to the shaft 210 by a conventional fixing manner, the roll body 220 will elongate very little due to thermal expansion, but because the coefficient of thermal expansion of the shaft is significantly greater than the coefficient of thermal expansion of the roll body 220, the compression force applied to the roll body 220 may be significantly affected.

[0039] According to the embodiments disclosed herein, the roll body 220 as one piece is spaced apart from the shaft 210, and the roll body 220 is fixed in place since the movable flange 240, which will be explained below, moves relative to the shaft 210 and pushes the roll body 220. Thus, it is possible to fix the roll body 220 in place, even though the roll body 220 is made of a material with a coefficient of thermal expansion of that is significantly less than the coefficient of thermal expansion of the shaft 210 (such as fused silica). This will be explained in detail below.

[0040] As shown in Figs. 4 and 5, the roll body 220 of the pulling roll 200 according to the first embodiment is inserted and fixed between the fixing flange 230 and the movable flange 240 positioned on the shaft 210. Further, a step S is shown to be formed on the roll body 220 in Fig. 6, but, in order to prevent thermal stress from being concentrated on the indented area to cause any crack, such a step may not be formed on the roll body 220 (see a second embodiment of Figs. 7-9).

[0041] As shown in Fig. 6, the movable flange 240 comprises a sleeve 242 extending in the longitudinal direction of the shaft 210 and a cap 244 extending outward from the sleeve 242 in a radial direction. The sleeve 242 defines a hole 246 through which the shaft 210 passes, and is movable on the shaft 210.

[0042] Since the sleeve 242 is configured to extend in the longitudinal direction of the shaft 210, the sleeve 242 allows the movable flange 240 to smoothly move on the shaft 210 in the longitudinal direction of the shaft 210. In order to make the movable flange 240 movably engaged with the shaft 210, there should be a small gap between the movable flange 240 and the shaft 210. Due to this gap, the movable flange 240 may be inclined relative to the shaft 210, while the movable flange 240 is moving on the shaft 210. The bigger the inclination angle, the more likely the movable flange 240 is caught by the surface of the shaft 210 thereby disrupting the movement of the movable flange 240. However, since the movable flange 240 disclosed herein includes the sleeve 242 extending in the longitudinal direction of the shaft 210, the maximum inclination angle of the movable flange 240 relative to the shaft 210 is reduced (compared to when the movable flange 240 is not equipped with the sleeve 242). Thus, the movable flange may smoothly move on the shaft 210. Further, in order to facilitate the smooth movement of the movable flange 240 on the shaft 210, the ends of the sleeve 242 may be rounded or chamfered.

[0043] A space 214, which extends in longitudinal direction of the shaft 210, is formed within the shaft 210 at an end thereof. A coil spring 250 and a rod 260 are installed in the space 214, with one end of the coil spring 250 contacting an inner wall of the shaft 210 within space 214 and the other end contacting the rod 260. Through-holes 264 are formed in one end 262 of the rod 260, a slot 216 is formed in the shaft 210, and through-holes 246 are formed in the movable flange 240. Pins 270 pass through the slot 216 of the shaft 210 to be engaged with the through- holes 264 of the rod 260 and the through-holes 246 of the movable flange 240. Since the slot

216 extends in the longitudinal direction of the shaft 210, the pins 270 are movable in the longitudinal direction of the shaft 210 within the slot 216.

[0044] With the roll body 220 fixed between the fixing flange 230 and the movable flange 240, the coil spring 250 is compressed such that the coil spring 250 pushes the rod 260 away from an end 212 of the shaft 210 in the longitudinal direction of the shaft 210.

[0045] According to the above described features of the shaft 210, the movable flange 240 is movable relative to the shaft 210 in the longitudinal direction of the shaft 210. At the same time, the movable flange 240 pushes the roll body 220 away from the end 212 of the shaft 210 in the longitudinal direction of the shaft 210 by an elastic restoring force of the coil spring 250. Thus, not only does the movable flange 240 contact and support the roll body 220 at room temperature but the movable flange 240 also moves relative to the shaft 210 to maintain the contact and support of the roll body 220 even though the shaft 210 is thermally expanded in the longitudinal direction at a high temperature.

[0046] The roll body 220 is spaced apart from the shaft 210 and is fixed in place by only the movable flange 240 so that the roll body 220 rotates with the shaft 210. In embodiments, a convex portion may be formed at the end of the roll body 220, and a concave portion which receives the convex portion of the roll body 220 may be formed at the cap 244. Thus, even if the roll body 220 is subject to a radial force when contacting and drawing the glass ribbon 148 during the operation of the pulling roll 200, the roll body 220 is prevented from running out from the movable flange 240.

[0047] If the roll body 220 and the shaft 210 are not concentric, the roll body 220 will wobble as the shaft 210 rotates. As a result, a uniform drawing force may not be provided to the glass ribbon 148. In order to prevent this, the concave portion of the cap 244 may comprise an inclined surface 248 which is inclined radially and inwardly. The convex portion of the roll body 220 comprises an inclined surface 224 which is complementary to and contacts the inclined surface 248. The convex and concave portions are designed so that the roll body 220 and the shaft 210 are positioned to be concentric when the inclined surfaces 224, 248 contact each other. Thus, even if the inclined surfaces 224, 248 do not contact each other temporarily (due to a reaction force provided by the glass ribbon 148), the inclined surfaces 224, 248 will shortly return to the contacting status since the inclined surface 248 is pushing against the inclined surface 224. As a result, the cap 244 centers the roll body 220 about the shaft 210 and the outer surface of the roll body 220 becomes concentric with the axis of rotation of the shaft 210.

[0048] Further, in order to make the roll body 220 rotate with the shaft 210 (i.e., in order to prevent any slip from occurring between the roll body 220 and the movable flange 240) when the roll body 220 contact and draw the glass ribbon 148, a sufficient force should be applied to the movable flange 240 by the coil spring 250. The force may be calculated based on a torque applied to the roll body 220 by the glass ribbon 148, the friction coefficient between the movable flange 240 and the roll body 220. The coil spring 250 should maintain an elastic force even at a high temperature, and may, for example, be made of NIMONIC 90 material.

[0049] Further, in order to ensure that there no slippage between the roll body 220 and the movable flange 240, additional complementary grooves 226 and protrusions 249 may be formed on the inclined surfaces 224, 248. Further, in order to prevent any slip from occurring between the roll body 220 and the moving flange 240, the end of the roll body 220 may be non-circular (for example, elliptical), when viewed in the axial direction of the roll body 220.

[0050] The fixing flange 230 may be designed identically to the movable flange 240 in terms of the shape, except that the fixing flange 230 is fixed on the shaft 210. The fixing flange 230 can be integrally formed with the shaft 210 or the fixing flange 230, which may be a separate member, can be fixed on the shaft 210. The fixing manner may include various known fixing methods such as a thread engagement, a pin engagement, etc. Further, the end of the roll body 220, which is engaged with the fixing flange 230, is also designed identically to the end of the roll body 220 which is engaged with the movable flange 240. That is, the roll body 220 with the ends complementary to the flanges 230, 240 identical in terms of the shape is positioned between the two flanges 230, 240, thereby centering the roll body 220 and preventing the ends of the roll body 220 from running out from the flanges or slipping on the flanges 230, 240.

[0051] The roll body 220 has an inner diameter Dl greater than the outer diameter D2 of the shaft 210 and the outer diameter D3 of the sleeve 242. That is, there is a predetermined gap Gl between the roll body 220 and the shaft 210 and a predetermined gap G2 between the roll body 220 and the sleeve 242. The predetermined gaps Gl, G2 are set such that even though the shaft

210 or the sleeve 242 is at its greatest thermal expansion radially and outwardly, the shaft 210 or the sleeve 242 does not contact the roll body 220.

[0052] Figs. 7 to 9 show a pulling roll 300 according to a second embodiment. Fig. 7 is a plan view of the pulling roll 300 according to the second embodiment, Fig. 8 is a cross-sectional view taken along a line VII- VII in Fig. 7, and Fig. 9 is an enlarged view of a portion B in Fig. 8.

[0053] As shown in Figs. 7 to 9, in the pulling roll 300 according to the second embodiment, a roll body 320 is inserted and fixed between a fixing flange 330 and a movable flange 340 positioned on a shaft 310, and a coil spring 350 is installed outside the shaft 310. The movable flange 340 in the second embodiment has a design and function similar to the movable flange 240 in the first embodiment. That is, the movable flange 340 may also comprise a sleeve 342 and a cap 344 (similarly to the movable flange 240 in the first embodiment) to move on the shaft 310 and support the roll body 320.

[0054] The shaft 310 comprises a first spring seat 360 and a second spring seat 370 for mounting the coil spring 350. The first spring seat 360 is positioned on one end 312 of the shaft 310 and the second spring seat 370 is spaced apart from the first spring seat 360 in a longitudinal direction of the shaft 310. The first spring seat 360 can be integrally formed with the shaft 310 or the first spring seat 360, which can be a separate member, can be fixed to the shaft 310 by known fixing methods such as a thread engagement, a pin engagement, welding, etc. The second spring seat 370 includes a hole 372, and the second spring seat 370 is mounted to be movable to the shaft 310 in such a manner that the shaft 310 passes through the hole 372.

[0055] The coil spring 350 is positioned between the first spring seat 360 and the second spring seat 370. While the roll body 320 is fixed between the fixing flange 330 and the movable flange 340, the coil spring 350 is compressed and thus the coil spring 350 pushes the second spring seat 370 away from the end 312 of the shaft 310 in the longitudinal direction of the shaft 310. Thus, the movable flange 340 which is in contact with the second spring seat 370 is also pushed away from the end 312 of the shaft 310. The second spring seat 370 is optionally provided for a more stable seating of the coil spring 350. A pulling roll of another embodiment may not comprise the second spring seat 370, and in this case, the coil spring 350 may directly contact the movable flange 340.

[0056] While the movable flange 340 is movable relative to the shaft 310 in the longitudinal direction of the shaft 310, the roll body 320 is pushed away from the end 312 of the shaft 310 in the longitudinal direction of the shaft 310 by an elastic restoring force of the coil spring 350. Thus, not only does the movable flange 340 contact and support the roll body 320 at room temperature but the movable flange 340 also moves relative to the shaft 310 to maintain contact with and support the roll body 320 even though the shaft 310 is at its greatest thermal expansion in the longitudinal direction at high temperature.

[0057] The roll body 320 has an inner diameter D5 greater than the outer diameter D4 of the shaft 310. That is, there is a predetermined gap G3 between the roll body 320 and the shaft 310. The predetermined gap G3 is set such that even though the shaft 310 is at its greatest thermal expansion radially and outwardly, the shaft (310) does not contact the roll body 320.

[0058] Figs. 10 and 11 show pulling rolls 400, 500 according to a third embodiment and a fourth embodiment, respectively. The pulling rolls 400, 500 according to the third embodiment and the fourth embodiment are cantilevered stub pulling rolls, which extend over only a part of the full width of the glass ribbon 148 and have features similar to the above described pulling rolls 200, 300 according to the first embodiment and the second embodiment. More

specifically, the pulling roll 400 according to the third embodiment shown in Fig. 10 comprises a shaft 410, a roll body 420, a fixing flange 430, a movable flange 440 and a coil spring 450. The coil spring 450 is position inside the shaft 410. The pulling roll 500 according to the fourth embodiment shown in Fig. 11 comprises a shaft 510, a roll body 520, a fixing flange 530, a movable flange 540 and a coil spring 550. The coil spring 550 is positioned outside the shaft 510. The coil spring 550 is positioned between the first spring seat 560 and the second spring seat 570.

[0059] In the glass ribbon drawing apparatus of one embodiment, a portion of the shaft 210, 310, 410, 510 that includes the coil spring 250, 350, 450, 550, whether the coil spring 250, 350, 450, 550 is positioned inside or outside the shaft 210, 310, 410, 510, is positioned outside the FDM 120 and only a remainder of the pulling roll 200, 300, 400, 500 except for the portion positioned outside is positioned inside the FDM 120. That is, the above described portion of the shaft 210, 310, 410, 510 is not exposed to high temperature. Thus, performance of the coil springs 250, 350, 450, 550 is less influenced by temperature. [0060] In the pulling rolls 200, 400 according to the first embodiment and the third embodiment wherein the coil spring 250, 450 is installed inside the shaft 210, 410, the coil spring 250, 450 is not exposed to the outside so there is no risk that the hands of the operator will be caught in the coil spring 250, 450, thereby providing greatly improved safety to the operator. Meanwhile, since the pulling rolls 300, 500 according to the second embodiment and the fourth embodiment comprise the coil spring 350, 550 installed outside the shaft 310, 510, it would be advantageous in view of the simple structure and ease of manufacturing.

[0061] The above described pulling rolls 200, 300 according to the first embodiment and the second embodiment are full length pulling rolls positioned upstream of the stub pulling rolls 400, 500. Since the temperature of the glass ribbon 148 is reduced as the glass ribbon 148 is drawn in the draw direction 151, the full length pulling roll 200, 300 positioned upstream of the stub pulling rolls 400, 500 is exposed to considerably high temperatures, whereas the stub pulling rolls 400, 500 are exposed to relatively low temperatures. Thus, if the coil spring positioned outside the shaft of the stub pulling roll is positioned inside the FDM 120, then the coil spring will not be exposed to the operator and, at the same time, the performance of the coil spring will not be significantly influenced by temperature compared to the upstream full length pulling roll. Figs. 12 and 13 illustrate such a pulling roll.

[0062] Fig. 12 is a plan view showing a pulling roll according to a fifth embodiment, and Fig. 13 is a cross-sectional view taken along a line XII- XII in Fig. 12.

[0063] The stub pulling roll 600 of the fifth embodiment comprises a shaft 610, a roll body 620, a fixing flange 630, a movable flange 640, a coil spring 650 and a spring seat 660. The coil spring 650 is positioned outside the shaft 610 and between the spring seat 660 and the movable flange 640. The spring seat 660 is positioned on a portion of the shaft 610, which is positioned inside the FDM 120. Thus, since the coil spring 650 is positioned between the spring seat 660 and the movable flange 640, the coil spring 650 is also positioned inside the FDM 120. With the roll body 620 fixed between the fixing flange 630 and the movable flange 640, the coil spring 650 is compressed such that the coil spring 650 pushes the movable flange 640 away from an end 612 of the shaft 610 in the longitudinal direction of the shaft 610.

[0064] Since the spring seat 660 of the fifth embodiment is positioned closer to the roll body 620 (compared to the first spring seat 410 of the fourth embodiment), no spring seat is provided between the coil spring 650 and the movable flange 640. However, the technical idea of the present disclosure is not limited to this embodiment, and it is also possible to provide a spring seat between the coil spring 650 and the movable flange 640, for example, by adjusting the length of the coil spring 650 while providing a sufficient force to the roll body 620.

[0065] In the glass ribbon apparatus 150 according to one embodiment shown in Fig. 2, since the pulling roll 200 according to the first embodiment and the pulling roll 600 according to the fifth embodiment are advantageous in view of their safety, they may be adopted for the full length pulling roll and the stub pulling roll, respectively. However, the glass ribbon drawing apparatus according to other embodiments may adopt the pulling roll 300 according to the second embodiment as the full length pulling roll and the pulling roll 400, 500 according to the third or fourth embodiment as the stub pulling roll.

[0066] In the pulling roll 200 according to the first embodiment, the movable flange 240 moves on the shaft 210 relative to the shaft 210. When glass condensate drops and accumulates at a region of the shaft 210 where the movable flange 240 moves, unnecessary stress may be exerted on the roll body 220. That is, in a state that the shaft 210 has been thermally expanded at a high temperature, the glass condensate may drop and accumulates on a portion of the shaft 210 moved relative to the movable flange 240. Then, if the shaft 210 contracts to its original length as the pulling roll 200 returns to room temperature, the accumulated glass condensate on the shaft 210 moves toward the movable flange 240 and is caught in the movable flange 240. Accordingly, a contraction force of the shaft 210 is transmitted via the movable flange 240 to the roll body 220 so that the roll body 220 may be damaged or destroyed.

[0067] Figs. 14a and 14b show a part of a pulling roll according to a sixth embodiment. Fig. 14a shows a part of the pulling roll, which is not thermally expanded at a room temperature. Referring to Fig. 14a, the sleeve 242 of the movable flange 240 extends to at least a portion of a region C of the shaft 210 where the glass condensate is likely to drop. The sleeve 242 of the movable flange 240 comprises an inner surface 252 facing an outer peripheral surface of the shaft 210, and a recess 258 is formed at an end 254 of the inner surface 252, which is the end farthest from the roll body 220. [0068] Fig. 14b shows a part of the pulling roll, which is thermally expanded at a high temperature. Referring to Fig. 14b, as the shaft 210 is thermally expanded in the longitudinal direction of the shaft 210, the shaft 210 moves in a direction indicated by an arrow T, relative to the movable flange 240. However, since the sleeve 242 of the movable flange 240 extends to the region C of the shaft 210 where the glass condensate is likely to drop, the glass condensate drops on the sleeve 242 and the accumulated glass G is formed on the sleeve 242. Thus, the accumulated glass is prevented from being formed on the shaft 210. Further, although the glass condensate drop and is accumulated on the shaft 210 (beyond the region C), the accumulated glass merely enters into the recess 258 but is not caught in the movable flange 240 when the shaft contracts. Thus, stress is not exerted to the movable flange 240 and the roll body 220.

[0069] The technical idea of the present disclosure is not limited to the above described embodiments and the examples shown in the accompanying drawings. It would be obvious to a person of ordinary skill in the art that various substitutions, modifications, and changes are possible within the scope of the technical idea of the present disclosure.

Claims

WHAT IS CLAIMED IS:

1. A pulling roll for drawing a glass ribbon, comprising:

a roll body comprising a central passage extending longitudinally therethrough;

a shaft extending through the central passage and spaced apart from the roll body;

a first flange movably positioned on the shaft, the first flange movable in a longitudinal direction of the shaft; and

a spring configured to push the first flange in the longitudinal direction of the shaft.

2. The pulling roll according to Claim 1 , wherein the pulling roll is a full length pulling roll.

3. The pulling roll according to Claim 1 , wherein the pulling roll is a stub pulling roll.

4. The pulling roll according to any one of Claims 1 to 3, wherein the roll body comprises a fused silica material.

5. The pulling roll according to Claim 4, wherein the first flange comprises:

a sleeve slidably engaged with the shaft; and

a cap extending outward from the sleeve, the cap contacting the roll body so that the first flange supports the roll body.

6. The pulling roll according to Claim 5, wherein the roll body and the cap comprise a convex portion and a concave portion which receives the convex portion.

7. The pulling roll according to Claim 6, wherein the convex portion and the concave portion comprises complementary inclined surfaces that contact each other.

8. The pulling roll according to Claim 7, wherein the inclined surfaces comprise a groove and a protrusion that are complementary to each other.

9. The pulling roll according to Claim 5, wherein the cap is configured to center the roll body about the shaft.

10. The pulling roll according to Claim 5, wherein the sleeve comprises an inner surface facing the shaft and a recess positioned at one end of the inner surface.

1 1. The pulling roll according to Claim 1 , wherein the spring is a coil spring positioned inside the shaft.

12. The pulling roll according to Claim 1 , wherein the spring is a coil spring installed outside the shaft.

13. The pulling roll according to Claim 11, further comprising:

a rod installed inside the shaft and engaged with the spring; and

a pin coupling the first flange to the rod, the shaft including at least one slot extending in the longitudinal direction of the shaft within which the pin is movable in the longitudinal direction of the shaft.

14. The pulling roll according to any one of Claims 1 to 3, further comprising:

a second flange fixed on the shaft, the roll body positioned between the first flange and the second flange.

15. The pulling roll according to Claim 12, wherein the spring is extendable while surrounding at least a portion of the shaft.

16. An apparatus for drawing a glass ribbon, comprising:

at least a pair of first pulling rolls; and

at least a pair of second pulling rolls positioned downstream of the pair of first pulling rolls along a pulling path,

wherein the at least a pair of first pulling rolls are full length pulling rolls and the at least a pair of second pulling rolls are stub pulling rolls.

17. A method for drawing a glass ribbon, comprising:

drawing the glass ribbon with at least a pair of pulling rolls, the pulling rolls including a shaft, a roll body rotatable with the shaft, a movable flange positioned on the shaft and supporting the roll body, a spring installed with the shaft and applying a force against the movable flange in a longitudinal direction of the shaft, the roll body comprising a fused silica material and spaced apart from the shaft, the drawing step further comprising moving the movable flange in the longitudinal direction of the shaft by means of the spring, so that the movable flange maintains the support of the roll body while drawing the glass ribbon.

18. The method according to Claim 17, wherein the movable flange comprises:

a sleeve slidably engaged with the shaft; and

a cap extending from the sleeve in an outward direction, the cap contacting the roll body so that the movable flange supports the shaft.

19. The method according to Claim 18, wherein the roll body and the cap comprise a convex portion and a concave portion which receives the convex portion.

20. The method according to Claim 18 or 19, wherein the sleeve comprises an inner surface facing the shaft and a recess positioned at one end of the inner surface.