JP2012101991A - Molten glass transfer tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve filling efficiency of molten glass in a molten glass transfer tube having a noble metal-made double tube structure in a vacant state at the time of start-up or the like, while facilitating temperature control of the molten glass during heating by applying an electric current, and saving electric power required for the heating.SOLUTION: The molten glass transfer tube 12 has a double tube structure comprising a noble metal-made outer tube 15 and a noble metal-made inner tube 16 connected to the inner peripheral surface of the outer tube 15 by a plurality of ribs 17 having through-holes 17a which communicate with one another in the tube axial direction. In a state where a space S2 between the inner surface of the outer tube 15 and the outer surface of the inner tube 16 is filled with molten glass G, the molten glass G is circulated in the internal space S1 of the inner tube 16 while heating the outer tube 15 by applying an electric current. The inner tube 16 is segmented into a plurality of pieces in the tube axial direction and made discontinuous, and the segmented separate inner tubes 16 are supported by the outer tube 15 via the ribs 17.

Description

  The present invention relates to a molten glass transfer tube made of a noble metal for transferring molten glass. Specifically, in order to reduce bubbles generated in the molten glass, the molten glass transfer tube includes an outer tube and an inner tube. The present invention relates to an improved technique for a double pipe structure.

  In general, when glass articles such as thin glass are continuously formed, for example, after the glass raw material is heated and melted in the molten glass in the glass melting chamber, the molten glass undergoes various processes such as a clarification process and a stirring process. It is continuously supplied to a molding apparatus (molded body). At this time, the molten glass melted in the glass melting chamber is transferred to a forming device by circulating the inside of a transfer pipe made of noble metal (see, for example, Patent Document 1).

  According to Patent Document 2, when molten glass is circulated inside a noble metal transfer tube, oxygen bubbles are generated in the molten glass in the process. And if this oxygen bubble is left as it is, the problem that the defect resulting from an oxygen bubble will be formed in the glass article shape | molded by a shaping | molding apparatus may arise. In particular, in the case of glass substrates for flat panel displays such as liquid crystal display panels, high product quality is required. Therefore, when defects due to oxygen bubbles are formed, the required quality is satisfied. It is easy to invite a situation that must be handled as a defective product.

  The reason why oxygen bubbles are formed in the molten glass as described above is described as follows according to Patent Document 2. That is, depending on the external environment of the transfer pipe made of noble metal (for example, when the hydrogen partial pressure in the external environment is low), hydrogen derived from moisture in the molten glass permeates through the transfer pipe made of noble metal and releases out of the pipe. It becomes easy to be done. As a result, the oxygen concentration derived from moisture in the molten glass is increased, oxygen bubbles are generated in the molten glass, and the glass bubbles are defective due to the oxygen bubbles.

  Therefore, in order to maintain the high quality of the glass article, it is indispensable to take measures to reduce oxygen bubbles in the molten glass. Therefore, for example, in Patent Document 2, a transfer pipe for circulating molten glass includes a noble metal outer pipe (outer noble metal jacket) and a noble metal inner pipe (inner noble metal jacket) connected to the inside by a web. It has been proposed to reduce the oxygen bubbles in the molten glass.

  In detail, it is the structure which distribute | circulates the molten glass used for shaping | molding of a glass article to the inside of an inner tube in the state with which the molten glass was filled in the space between an outer tube and an inner tube. In this way, the presence of the molten glass between the outer tube and the inner tube suppresses the situation in which hydrogen derived from moisture in the molten glass flowing inside the inner tube permeates to the outside. The respective concentrations of hydrogen and oxygen derived from moisture in the molten glass flowing through the inside of the tube are appropriately maintained, and oxygen bubbles are hardly formed.

  Patent Document 2 also discloses that when the molten glass is transferred by the transfer tube, the transfer tube is connected to both ends of the outer tube to electrically heat the transfer tube. This is for heating the molten glass transferred by the transfer pipe and maintaining the viscosity of the molten glass inside the transfer pipe appropriately.

JP 2007-145668 A JP 2003-95663 A

  By the way, in Patent Document 2, since the outer tube connected to the electric heating circuit and the inner tube connected via the rib are continuous in the tube axis direction, when the outer tube is energized by the electric heating circuit, Current flows over the entire length of the tube. Therefore, the outer tube and the inner tube are each heated by energization.

  However, since a complicated closed circuit is formed between the outer tube and the inner tube via a rib, it is difficult to accurately manage the current flowing through the outer tube and the inner tube. In other words, it becomes difficult to strictly control the temperature of the outer tube and the inner tube, the temperature distribution varies widely inside the transfer tube, or in some cases, the inner tube is abnormally heated and blown, and the inner tube May cause a fatal problem in production that the molten glass cannot be distributed. For this reason, the transportation of the molten glass flowing through the inner space of the inner tube becomes unstable, which causes a problem in forming the glass article.

  Also, if the current flows through both the outer tube and the inner tube, the cross-sectional area of the current-carrying region is relatively larger than when the current flows only through the outer tube, so the overall resistance value is reduced. The current value will increase. As a result, power consumption during energization heating becomes unreasonably large, and it is extremely difficult to save power.

  Furthermore, since the outer tube and the inner tube are each continuous in the tube axis direction, the inner space of the inner tube and the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube are independent from each other. It is a space. Therefore, when the molten glass is filled into the empty transfer pipe at the time of starting the transfer pipe or the like, it is necessary to separately fill the two independent spaces with the molten glass, and workability is very poor.

  In view of the above circumstances, the present invention is a molten glass transfer tube having a double tube structure made of a noble metal, which facilitates temperature management of the molten glass at the time of energization heating and saves power required for the energization heating. It is a technical problem to improve the efficiency of filling molten glass in an empty state such as when the transfer pipe is started.

  In order to solve the above problems, the present invention provides a noble metal inner pipe connected to an inner peripheral surface of the outer pipe by a noble metal outer pipe and a plurality of ribs having openings communicating in the pipe axis direction. A double tube structure comprising a tube, and while the outer tube is energized and heated while the outer tube is filled with molten glass in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube, the inner tube In the molten glass transfer pipe for circulating molten glass in the internal space of the pipe, the inner pipe is divided into a plurality of pieces in the pipe axis direction to be discontinuous, and the divided inner pipes are provided with the ribs. It is characterized by being supported by the outer tube via.

  According to such a configuration, since the inner pipe is divided into a plurality of parts in the pipe axis direction and is discontinuous, a gap is formed between the individual inner pipes adjacent to each other in the pipe axis direction. Therefore, even if each divided inner tube is supported by the outer tube via the rib, no current flows directly between the adjacent inner tubes when the outer tube is energized and heated. As a result, when the outer tube is energized and heated, a current flows mainly through the outer tube, so that the inner tube is hardly energized and heated. Therefore, the temperature of the molten glass can be easily and accurately managed during energization heating only by managing the current flowing through the outer tube. Moreover, since no current substantially flows through the inner tube when the outer tube is energized and heated, unnecessary power consumption can be suppressed, and the power supplied during energization heating can be saved. Further, since the gap is formed as described above between the inner pipes adjacent to each other in the tube axis direction, this gap is used when the empty transfer pipe is filled with molten glass at the time of starting the transfer pipe. It is possible to distribute the molten glass through Therefore, even if the molten glass is not separately filled into the inner space of the inner tube and the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube, the molten glass is efficiently introduced through the spaces in both spaces. It is possible to improve the working efficiency.

  Said structure WHEREIN: It is preferable that the said outer tube | pipe has a gas discharge part for removing the bubble contained in the molten glass which exists in the space between the inner peripheral surface and the outer peripheral surface of the said inner tube | pipe.

  If it does in this way, the bubble contained in the molten glass which exists in the space between the internal peripheral surface of an outer tube | pipe and the outer peripheral surface of an inner tube | pipe can be removed. Therefore, it is possible to efficiently heat the molten glass flowing through the inner space of the inner tube without being hindered by heat-conductive air bubbles due to heat conduction by the outer tube.

  Said structure WHEREIN: It is preferable that the outer peripheral surface of the said outer tube | cover is covered with the molten glass.

  In this way, the rate at which hydrogen derived from the moisture of the molten glass existing in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube permeates outwardly of the outer tube can be reduced. it can.

  Said structure WHEREIN: It is preferable that the said outer tube | pipe has a molten glass discharge part for discharging | emitting the molten glass which exists in the space between the inner peripheral surface of the said outer tube | pipe, and the outer peripheral surface of the said inner tube | pipe.

  In this way, the molten glass existing in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube can be discharged through the molten glass discharge unit, and new molten glass can be appropriately replenished in the space. it can.

  In the above configuration, the flow rate of the molten glass in the inner space of the inner tube is configured to be faster than the flow rate of the molten glass in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube. It is preferable. The flow rate of the molten glass in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube may be substantially zero when the molten glass in the space is stagnant. Including.

  In this way, when the molten glass is circulated in the inner space of the inner tube with the molten glass filled in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube, the tube It becomes difficult for molten glass to pass through the gap between the divided inner pipes adjacent in the axial direction. In particular, the ratio of the molten glass existing in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube invading into the molten glass that is distributed in the inner space of the inner tube and used for molding glass products Can be effectively reduced.

  In the above configuration, the outer tube and the inner tube are made of, for example, platinum or a platinum alloy.

  As described above, according to the present invention, in the molten glass transfer pipe having a double pipe structure composed of a noble metal outer pipe and an inner pipe, the inner pipe is divided into a plurality of pieces in the tube axis direction and becomes discontinuous. Therefore, the temperature management of the molten glass at the time of energization heating of the outer tube and the labor saving of the power required for the energization heating can be achieved at the same time. In addition, by utilizing the gap formed between the divided inner tubes, the empty transfer tube can be efficiently filled with molten glass at the time of starting the transfer tube.

It is a figure which shows the structure of the manufacturing apparatus of the plate glass provided with the molten glass transfer tube which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view of the molten glass transfer pipe concerning this embodiment. It is a cross-sectional view of the molten glass transfer tube according to the present embodiment. It is a cross-sectional view showing a modification of the molten glass transfer tube according to the present embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a configuration of a plate glass manufacturing apparatus including a molten glass transfer tube according to an embodiment of the present invention. In this manufacturing apparatus 1, a stirring tank 4 is connected to a downstream side of a melting chamber 2 disposed at an upstream end via a clarification chamber 3, and the viscosity of the molten glass G is adjusted to the stirring tank 4 on the downstream side. The pot 5 which is a volume part which mainly performs is connected. Furthermore, a flow path area restricting portion 6 whose diameter gradually decreases as it moves downward is formed at the lower portion of the pot 5, and a small diameter pipe 7 is connected to the downstream end of the flow path area restricting portion 6. A large-diameter pipe 9 having a bent portion 8 is provided on the downstream side of the small-diameter pipe 7. And the molten glass G is supplied to the molded object 11 from the downstream end part 10 of this large diameter pipe | tube 9, and the molten glass G is made into a plate-shaped form in this molded object 11. FIG.

  In this embodiment, the molded body 11 has a substantially wedge-shaped cross section and executes the overflow downdraw method. The molded body 11 is configured to mold the molten glass G into a plate shape as follows. . First, molten glass G is continuously supplied to an overflow groove (not shown) formed in the upper part of the molded body 11, and the molten glass G overflows from the overflow groove and flows down along the side wall surfaces on both sides of the molded body 11. . And the molten glass G which flowed down is united in the lower top part of the molded object 11, respectively, and it is set as one plate-like form. Thereafter, when the plate-shaped glass molded product of this form is solidified, it is pulled out downward while being held by a pulling roller, thereby obtaining a plate glass to finally become a product. In addition, the plate glass manufactured in this way is 0.1-1.0 mm in thickness, for example, Flat panel displays, such as a liquid crystal display and an organic EL display, Organic EL lighting, Substrates, such as a solar cell, and a protective cover Used for

  The melting chamber 2 and the clarification chamber 3, the clarification chamber 3 and the agitation tank 4, and the agitation tank 4 and the pot 5 are connected by molten glass transfer pipes 12, 13, and 14. In addition, since these molten glass transfer pipes 12, 13, and 14 have substantially the same configuration, in the following, the molten glass transfer pipe 12 that connects the melting chamber 2 and the clarification chamber 3 is taken as an example. A specific configuration will be described.

  As shown in FIG. 2, the molten glass transfer tube 12 has a double tube structure including an outer tube 15 made of noble metal and an inner tube 16 made of noble metal housed in the outer tube 15. Examples of the noble metal constituting the inner tube 16 and the outer tube 15 include platinum or a platinum alloy.

  The inner tube 16 is divided into a plurality of pieces in the tube axis direction and is discontinuous. The divided individual inner pipes 16 are supported by the outer pipe 15 in a state of being connected to the inner peripheral surface of the outer pipe 15 via ribs 17.

  One rib 17 is provided at a predetermined position in the tube axis direction of the outer peripheral surface of each inner tube 16 (for example, the central portion in the tube axis direction of each inner tube 16). As shown in FIG. It is formed in a disk shape so as to surround the entire circumference at the same position in the tube axis direction of the outer peripheral surface of 16. Furthermore, each rib 17 has a through hole 17a that forms an opening communicating with the tube axis direction. In the illustrated example, a plurality of the through holes 17a are formed at intervals (for example, equal intervals) in the circumferential direction of the ribs 17. The opening of the rib 17 is not limited to the through-hole 17a. For example, as shown in FIG. 4, the rib 17 is formed on the outer peripheral surface of the inner tube 16 at intervals in the circumferential direction. You may comprise the opening part connected to the pipe-axis direction by the space | gap between the ribs 17 adjacent to the circumferential direction. Here, in FIG.3 and FIG.4, illustration of the refractory 18 is abbreviate | omitted for convenience of explanation.

  Furthermore, as shown in FIG. 2, the periphery of the outer tube 15 is covered with a refractory 18. A rib 19 is also provided on the outer peripheral surface of the outer tube 15, and the outer tube 15 is reinforced by the rib 19 and positioned with respect to the inside of the refractory 18. As shown in FIG. 3, the rib 19 of the outer tube 15 also has a through hole 19a that forms an opening communicating with the tube axis direction. The opening of the rib 19 of the outer tube 15 is not limited to the through hole 19a. For example, as shown in FIG. 4, the rib 19 is spaced from the outer peripheral surface of the outer tube 15 in the circumferential direction. And an opening that communicates in the tube axis direction may be formed by the gaps between the ribs 19 in the circumferential direction.

  As shown in FIG. 2, when manufacturing the plate glass, the inner tube is filled with the molten glass G in the space S <b> 2 between the inner peripheral surface of the outer tube 15 and the outer peripheral surface of the inner tube 16. The molten glass G utilized for manufacture of plate glass is distribute | circulated in 16 internal space S1. The reason for this is to keep the hydrogen partial pressure outside the inner tube 16 properly and prevent hydrogen from permeating from the molten glass G flowing through the space S1.

  Furthermore, in this embodiment, the space S3 between the outer peripheral surface of the outer tube 15 and the inner wall of the refractory 18 is also filled with the molten glass G, and the outer peripheral surface of the outer tube 15 is covered with the molten glass G. It is in the state. In this way, the rate at which hydrogen derived from the moisture of the molten glass G existing in the space S <b> 2 between the inner peripheral surface of the outer tube 15 and the outer peripheral surface of the inner tube 16 permeates outward of the outer tube 15. Can be reduced.

  While the molten glass G is circulated in this way, the outer tube 15 is energized and heated by the power sources 23 and 24 connected between the electrodes 20, 21 and 22 provided at predetermined positions of the outer tube 15, and the molten glass G The viscosity is properly maintained.

  Here, as described above, since the inner tube 16 is divided into a plurality of pieces in the tube axis direction and becomes discontinuous, there is a gap S4 between the individual inner tubes 16 adjacent in the tube axis direction. It is formed. As a result, even when the divided individual inner pipes 16 are connected to the outer pipe 15 via the ribs 17, current is directly applied between the divided individual inner pipes 16 when the outer pipe 15 is energized and heated. There is no flow. Therefore, when the outer tube 15 is energized and heated, a current flows mainly through the outer tube 15, so that the inner tube 16 is not energized and heated. Accordingly, it is difficult for heating failure due to abnormal heating of the inner tube 16 or the like, and the temperature management of the molten glass G during the heating with current is easily and accurately performed only by mainly managing the heating state of the outer tube 15 by the current flowing through the outer tube 15. Can be done. In addition, it is preferable that the rib 17 is attached to only one place in the tube axis direction for each individual inner tube 16.

  Moreover, since no current substantially flows through the inner tube 16 when the outer tube 15 is energized and heated, unnecessary power consumption can be suppressed, and the power supplied during energization heating can be saved.

  Further, when the empty glass transfer pipe 12 is filled with the molten glass G at the time of starting the plate glass manufacturing apparatus 1, the gap S4 formed between the divided inner pipes 16 adjacent to each other in the pipe axis direction is formed. The molten glass G can be circulated through. For this reason, both the spaces S1, S2 can be obtained without separately filling the molten glass G into the internal space S1 of the inner tube 16 and the space S2 between the inner peripheral surface of the outer tube 15 and the outer peripheral surface of the inner tube 16. It is possible to efficiently fill the molten glass G through the gap S4, and to improve the working efficiency.

  In addition, the space | interval (tube-axis direction dimension) of the space | gap S4 between the adjacent inner tubes 16 is the inner space S1 of the inner tube 16, the inner peripheral surface of the outer tube 15, and the outer periphery of the inner tube 16 at the time of plate glass manufacture. It is preferably set so that the molten glass G does not circulate between the space S2 and the surface, and specifically, for example, it is preferably about 10 to 30 mm. Of course, even in this case, when the flow rate of the molten glass G is slower than that at the time of production of the plate glass, such as when the plate glass production apparatus 1 is started, the molten glass G is placed in the space through the gap S4 between the adjacent inner tubes 16. It is possible to circulate between S1 and space S2.

  Further, at the time of manufacturing the plate glass, the flow rate of the molten glass G in the inner space S1 of the inner tube 16 is greater than the flow rate of the molten glass G in the space S2 between the inner peripheral surface of the outer tube 15 and the outer peripheral surface of the inner tube 16. Is also set to be faster. If it does in this way, the situation where the molten glass G distribute | circulates the space | gap S4 between the adjacent inner pipes 16 by the flow velocity difference of the molten glass G can be prevented reliably. Since the molten glass G in the space S2 is arranged for the purpose of appropriately maintaining the hydrogen partial pressure outside the inner tube 16, the molten glass G in the space S2 has a substantial flow rate in a stationary state. It may be zero. For the same reason, the flow rate of the molten glass G existing in the space S3 between the outer peripheral surface of the outer tube 15 and the inner wall of the refractory 18 may be substantially zero.

  The outer tube 15 is provided with a gas discharge tube 25 for removing bubbles contained in the molten glass G in the space S2 between the inner peripheral surface thereof and the outer peripheral surface of the inner tube 16, and in the space S2 A molten glass discharge pipe 26 for discharging the existing molten glass G is provided. If the former gas discharge pipe 25 is used, bubbles contained in the molten glass G existing in the space S2 can be removed, so that heat conduction by energization heating of the outer pipe 15 is obstructed by bubbles having heat insulation performance. Without this, the molten glass G flowing through the internal space S1 of the inner tube 16 can be efficiently heated. Further, if the latter molten glass discharge pipe 26 is used, the molten glass G existing in the space S2 can be appropriately discharged to replenish the space S2 with new molten glass G. In addition, although not shown in figure, the molten glass discharge pipe 26 becomes a structure which can open and close a flow path suitably. Specifically, for example, when the molten glass discharge pipe 26 is energized and heated, the solidified glass solidified inside the molten glass discharge pipe 26 and closing the flow path is melted again, and the flow path is opened. It is configured. The gas discharge pipe 25 and the molten glass discharge pipe 26 may be provided at a plurality of locations of the outer pipe 15.

  In addition, this invention is not limited to the said embodiment, It can implement with a various form. For example, in the above-described embodiment, the case where the molten glass transfer tube is incorporated in a manufacturing apparatus that manufactures plate glass by the overflow downdraw method has been described. However, manufacture of manufacturing plate glass by another downdraw method such as the slot downdraw method is described. It may be incorporated into the device.

  Moreover, although the said embodiment demonstrated the structure which covers the outer peripheral surface of the outer tube | pipe 15 with the molten glass G, this molten glass G is abbreviate | omitted suitably according to the amount of hydrogen which permeate | transmits the exterior of the outer tube | pipe 15, etc. Can do.

DESCRIPTION OF SYMBOLS 1 Sheet glass manufacturing apparatus 2 Melting room 3 Clarification room 4 Stirrer tank 5 Pot 11 Molded body 12 Molten glass transfer pipe 15 Outer pipe 16 Inner pipe 17 Rib 17a Through hole 18 Refractory 19 Rib 19a Through hole 20, 21, 22 Electrode 23 , 24 Power supply 25 Gas discharge pipe 26 Molten glass discharge pipe G Molten glass

Claims (6)

A double pipe structure comprising a noble metal outer pipe and a noble metal inner pipe connected to the inner peripheral surface of the outer pipe by a plurality of ribs having openings communicating in the pipe axis direction; A molten glass transfer tube that circulates the molten glass in the inner space of the inner tube while energizing and heating the outer tube while the molten glass is filled in the space between the inner peripheral surface of the inner tube and the outer peripheral surface of the inner tube In
The inner pipe is divided into a plurality of pieces in the pipe axis direction to be discontinuous, and the divided inner pipes are supported by the outer pipe through the ribs. Glass transfer tube.   The said outer tube | pipe has a gas discharge part for removing the bubble contained in the molten glass which exists in the space between the inner peripheral surface and the outer peripheral surface of the said inner tube | pipe, It is characterized by the above-mentioned. The molten glass transfer tube as described.   The molten glass transfer tube according to claim 1, wherein an outer peripheral surface of the outer tube is covered with molten glass.   The said outer pipe | tube provided the molten glass discharge | emission part for discharging | emitting the molten glass which exists in the space between the internal peripheral surface and the outer peripheral surface of the said inner pipe | tube. The molten glass transfer tube according to claim 1.   The flow rate of the molten glass in the inner space of the inner tube is faster than the flow rate of the molten glass in the space between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube. The molten glass transfer tube according to any one of the above.   The molten glass transfer tube according to any one of claims 1 to 5, wherein the outer tube and the inner tube are made of platinum or a platinum alloy.

Images