TWI807047B - Method for manufacturing glass objects - Google Patents

Abstract

A method for manufacturing a glass article, comprising: a continuous production step of continuously supplying glass raw material 4 to molten glass 2 stored in a furnace 1, melting the raw material 4 to continuously produce new molten glass 2, and allowing the molten glass 2 to flow out of the furnace 1 through a tube 5 having an inner peripheral surface 5a made of platinum or a platinum alloy; and a starting step of starting the furnace 1 to a state where the continuous production step can be performed. In the temperature raising step, heating is performed by the burners 7 and 8 while reducing the contact between the ambient air in the furnace 1 and the inner peripheral surface 5 a of the tube 5 .

Description

Method for manufacturing glass objects

The present invention relates to a method of manufacturing a glass article, comprising: using a glass melting furnace to continuously generate molten glass to be a raw material of the glass article; and starting the furnace to a state where the step can be performed.

As is well known, glass articles represented by glass plates, glass tubes, glass fibers, etc. are produced by molding molten glass produced by melting glass raw materials into a predetermined shape. Here, Patent Document 1 discloses an example of a method of continuously producing molten glass using a glass melting furnace.

In the method disclosed in this document, glass raw materials are continuously supplied onto molten glass stored in a glass melting furnace, while glass raw materials are melted to continuously generate new molten glass, and the molten glass is flowed out of the furnace through an outflow passage (throat in this document). In addition, the inner peripheral surface of the outflow passage is usually made of platinum or a platinum alloy. [Prior art literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2003-183031

[Problem to be Solved by the Invention] Furthermore, when operating a glass melting furnace, it is necessary to start the furnace in a state where molten glass can be continuously produced. In order to raise the temperature inside the furnace from normal temperature at the start-up of the furnace, an air burner which mixes and burns a gaseous fuel such as natural gas with air or an oxygen burner which mixes and burns a gaseous fuel with oxygen is often used. By heating with these burners, when the temperature in the furnace rises to a temperature at which the glass raw material can be melted, the supply of the glass raw material into the furnace is started. Along with this, the glass raw material is melted, and the molten glass is gradually stored in the furnace.

However, the following problems arise in the start-up of the glass melting furnace of the above aspect.

That is, when an air burner or an oxygen burner is used to raise the temperature in the glass melting furnace, the feeding of air or oxygen into the furnace is continued, and the atmosphere in the furnace containing oxygen inevitably flows into and out of the passage along with this. As a result, the platinum or platinum alloy constituting the inner peripheral surface of the outflow passage is oxidized or volatilized.

The technical subject of the present invention made in view of the above situation is to suppress oxidation or volatilization of platinum or a platinum alloy on the inner peripheral surface of the outflow passage of the molten glass as much as possible when the temperature in the glass melting furnace is raised by heating with a burner and the furnace is started when the glass product is manufactured. [Means to solve the problem]

The present invention to solve the above-mentioned problems is a method of manufacturing glass articles, comprising: a continuous production step of continuously supplying glass raw materials to molten glass stored in a glass melting furnace, melting the glass raw materials to continuously produce new molten glass, and allowing the molten glass to flow out of the glass melting furnace through an outflow passage having an inner peripheral surface made of platinum or a platinum alloy; and a starting step of starting the glass melting furnace to a state where the continuous production step can be performed. A temperature raising step in which the burner raises the temperature in the glass melting furnace from normal temperature; and a raw material supply start step in which the glass raw material is started to be supplied to the glass melting furnace. In the temperature raising step, the ambient air in the glass melting furnace is heated with a burner while reducing the contact with the inner peripheral surface of the outflow passage.

According to this method, in the temperature raising step, the temperature in the furnace is raised from normal temperature by heating with the burner while the contact between the ambient air in the glass melting furnace and the inner peripheral surface of the outflow passage is reduced. Thereby, even when the ambient air in the furnace containing oxygen sent into the furnace with the use of the burner flows into the outflow passage or is about to flow into the outflow passage, oxidation or volatilization of platinum or platinum alloy constituting the inner peripheral surface of the outflow passage can be suppressed as much as possible.

In the method described above, it is preferable to prevent the ambient air in the glass melting furnace from contacting the inner peripheral surface of the outflow passage with a shielding material.

By preventing the ambient air in the glass melting furnace from contacting the inner peripheral surface of the outflow passage with the shielding material, the contact between the ambient air in the glass melting furnace and the inner peripheral surface of the outflow passage can be stably reduced.

In the above method, it is preferable to use a glass material as the shielding material.

The following effects can also be obtained by using the glass material to prevent the atmosphere in the furnace from coming into contact with the inner peripheral surface of the outflow passage. That is, members other than glass (for example, metal members, refractory materials, etc.) may be used as the masking material, but in this case, work for removing the masking material will be required. Moreover, there exists a possibility that a masking material may mix in a molten glass, and a malfunction may arise. If a glass material is used, as the temperature in the furnace rises, the glass material is soon melted to become a molten glass, and the molten glass obtained by melting the glass raw material is sent to a downstream step. Therefore, if a glass material is used as a masking material, the work of removing the masking material is not required, and the possibility of a problem caused by the masking material being mixed into the molten glass can be eliminated.

In this method, it is preferable to use a glass plate that covers the opening of the upstream end of the outflow passage as the glass material.

In this way, with the glass plate covering the opening of the upstream end of the outflow passage, the ambient air in the furnace containing oxygen can be reliably prevented from flowing into the outflow passage. This is more advantageous in suppressing oxidation or volatilization of platinum or platinum alloy constituting the inner peripheral surface of the outflow passage as much as possible.

In the above method, it is preferable that the composition of the glass material is the same as that of the molten glass.

In this way, the composition of the molten glass can be prevented from changing depending on the glass material, which is advantageous in utilizing the molten glass.

In the above method, preferably, the glass melting furnace includes an electrode movable between an entry position into the furnace and a retreat position retreating from the furnace, and in the continuous generating step, heating is performed by energizing the electrode at the entry position, and in the temperature raising step, heating is performed by a burner in a state where the ambient air in the glass melting furnace is prevented from contacting the electrode by covering the front end of the electrode at the retreat position with a cover member.

In this way, by covering the electrodes with the cover member, the contact between the electrodes and the atmosphere in the furnace can be reduced, and the electrodes can be protected from oxidation.

In the above method, the glass melting furnace may be used as the first glass melting furnace, and the outflow path may be used as the first outflow path. Through the first outflow path, the first glass melting furnace may be connected to a second glass melting furnace into which molten glass flowing out of the first glass melting furnace flows. The ambient air in the second glass melting furnace is in contact with the inner peripheral surface of the first outflow passage, and the ambient air in the second glass melting furnace is in contact with the inner peripheral surface of the second outflow passage for letting the molten glass flow out of the second glass melting furnace, and is heated by a burner.

In this way, not only in the first glass melting furnace but also in the second glass melting furnace, oxidation or volatilization of platinum or platinum alloy constituting the inner peripheral surface of the outflow passage (second outflow passage) can be suppressed as much as possible.

In the above method, in the continuous production step, it is preferable to heat the molten glass stored in the glass melting furnace only by electric heating.

In this way, compared with the case where the heating by the burner and the electric heating are used together, the ambient air in a glass melting furnace can be made dry. Thereby, it is easy to prevent the moisture in the ambient air in the furnace from being dissolved into the molten glass, and it is easy to reduce the β-OH value of the manufactured glass product. As a result, compaction at the time of heating a glass product can be reduced, and the glass product suitable for the alkali-free glass substrate for displays can be obtained.

Here, the term "alkali-free glass" refers to glass that does not substantially contain alkali components (alkali metal oxides), and specifically refers to glass in which the weight ratio of alkali components is 3000 ppm or less. Furthermore, the weight ratio of the alkali component is preferably not more than 1000 ppm, more preferably not more than 500 ppm, most preferably not more than 300 ppm. [Effect of the invention]

According to the present invention, when the temperature in the glass melting furnace is raised by the heating of the burner and the furnace is started up during the production of glass goods, the oxidation or volatilization of platinum or platinum alloy constituting the inner peripheral surface of the outflow passage of molten glass can be suppressed as much as possible.

<First Embodiment> Hereinafter, the manufacturing method of the glass article which concerns on 1st Embodiment of this invention is demonstrated, referring drawings.

1 and 2 show aspects in which continuous production steps are performed in a glass melting furnace 1 (hereinafter simply referred to as furnace 1 ).

In the continuous production step, while the temperature in the furnace 1 (the molten glass) is maintained at the working temperature (for example, 1450°C to 1550°C), the molten glass 2 stored in the furnace 1 is heated by electricity through the electrode 3, and the glass raw materials 4 continuously supplied to the surface 2a of the molten glass 2 are sequentially melted to continuously generate new molten glass 2, and the molten glass 2 is flowed out of the furnace 1 through the pipe 5 serving as an outflow path (first outflow path). In this continuous production step, the molten glass 2 is heated only by the energization heating of the electrodes 3 .

The molten glass 2 produced in the continuous production step is sent to downstream steps including a forming step, and through processes such as shaping the molten glass 2 in the downstream step, glass articles (such as glass plates, glass tubes, glass fibers, etc.) are manufactured.

The furnace 1 used in this embodiment has a rectangular cross-sectional shape in plan view. This furnace 1 has a front wall 1a at the upstream end in the flow direction T of the glass raw material 4 in the furnace 1, a rear wall 1b at the downstream end, a pair of side walls 1c and 1d, a top wall 1e, and a bottom wall 1f. These furnace walls 1 a - 1 f are each made of a refractory (in this embodiment, a high zirconia electroformed refractory brick).

A plurality of (three in this embodiment) screw feeders 6 for supplying glass raw materials 4 into the furnace 1 are arranged in parallel on the front wall 1 a. Each screw feeder 6 is inserted into the opening part 1aa formed in the front wall 1a without gap. In addition, tin oxide is added to the glass raw material 4 supplied from the screw feeder 6 as a clarifying agent.

Here, in this embodiment, the screw feeder 6 is used for the supply of the glass raw material 4, but the feeder other than the screw feeder 6 may be used. As an example of a feeder, a vibration feeder, a pusher, a blanket feeder, etc. can also be used. From the viewpoint of improving the airtightness in the furnace 1, it is preferable to use the screw feeder 6 or the vibration feeder. In addition, in this embodiment, although the several screw feeders 6 were used, the number of screw feeders 6 may be only one.

The pipe 5 for letting the molten glass 2 flow out is arrange|positioned on the rear wall 1b. The inner peripheral surface 5a of the tube 5 is made of platinum or a platinum alloy.

A pair of burners 9 consisting of one air burner 7 and one oxygen burner 8 are respectively arranged on the side wall 1c and the side wall 1d. In this embodiment, three pairs of burners 9 are arranged on the side wall 1c, and two pairs of burners 9 are arranged on the side wall 1d. In addition, in this embodiment, the air burner 7 and the oxygen burner 8 are arranged as a pair, but the number of the air burner 7 and the oxygen burner 8 may differ. In addition, the air burner 7 and the oxygen burner 8 may also be arranged on the top wall 1e. In the execution of the continuous generation step in this embodiment, both the air burner 7 and the oxygen burner 8 are in a state of being stopped in each of the five burner pairs 9 in total.

The air burner 7 is a burner that mixes gaseous fuel such as natural gas with air and burns it. On the other hand, the oxygen burner 8 is a burner that mixes and burns gaseous fuel and oxygen.

As shown by the two-dot chain line in FIG. 2 , the two burners 7 and 8 can inject flames 7 a and 8 a from the side wall 1 c (side wall 1 d ) to the opposite side wall 1 d (side wall 1 c ), respectively. Furthermore, the thermal power of the oxygen burner 8 is higher than that of the air burner 7 . On the other hand, the flame 7a injected by the air burner 7 is wider than the flame 8a injected by the oxygen burner 8 in plan view. In addition, in this embodiment, the air burner 7 can be detached from the side wall 1c (side wall 1d) in the state which stopped the operation. The oxygen burner 8 can also be detached from the side wall 1c (side wall 1d) in a stopped state.

The electrodes 3 arranged on the bottom wall 1f are formed in a rod shape. The electrode 3 is movable between an entry position into the furnace 1 from the bottom wall 1f (the position of the electrode 3 in FIG. 1 ) and a retracted position from the furnace 1 (the position of the electrode 3 in FIG. 3 mentioned later). The electrode 3 is made of molybdenum, for example.

During the execution of the continuous generation step, the molten glass 2 is heated by means of the electrodes 3 located in the entry position and in a state immersed in the molten glass 2 in the furnace 1 . By adjusting the voltage applied to the electrode 3 , the energy generated by the electrode 3 (heat energy given to the molten glass 2 ) can be adjusted. And as the electrode 3 heats the molten glass 2, the glass raw material 4 on the surface 2a of the molten glass 2 is indirectly heated and melt|dissolved. Thereby, new molten glass 2 is produced|generated sequentially.

Here, in this embodiment, the molten glass 2 is heated by the rod-shaped electrode 3, but in addition to the rod-shaped electrode 3, or instead of the rod-shaped electrode 3, the molten glass 2 may be heated by a plate-shaped electrode or a block-shaped electrode respectively arranged on the pair of side walls 1c and 1d.

In the present embodiment, when the furnace 1 is started up to a state where the continuous production step can be performed, the following start-up step is performed.

In the starting step, a first temperature raising step ( FIG. 3 ), a second temperature raising step ( FIG. 5 ), a raw material supply start step ( FIG. 6 ) and an electric heating start step ( FIG. 8 ) are carried out. The first temperature raising step is a step of raising the temperature in the furnace 1 from normal temperature (especially a temperature without cooling or heating, for example, 20±15° C.) by the air burner 7 , and the second temperature raising step is a step of raising the temperature in the furnace 1 by the oxygen burner 8 . Step 4, the electric heating start step is a step of starting electric heating of the molten glass 2 stored by melting the glass raw material 4 . In this embodiment, the temperature raising step is constituted by both the first temperature raising step and the second temperature raising step.

First, as a preparation for the start-up step, before starting the first temperature raising step, as shown in FIG. The first glass plate 10 is located directly above the electrode 3 , so the front end (upper end) of the electrode 3 is covered by the first glass plate 10 . In this way, the electrodes 3 are protected by the first glass plate 10 . The electrode 3 is covered with the first glass plate 10 until the first glass plate 10 melts as the temperature in the furnace 1 rises. This prevents the oxygen-containing atmosphere in the furnace 1 from coming into contact with the electrode 3 during the period from the start of the first temperature raising step to the melting of the first glass plate 10 , thereby avoiding oxidation of the electrode 3 as much as possible. In addition, the space formed between the first glass plate 10 and the electrode 3 is filled with a plurality of glasses (not shown) formed in a block shape.

Here, in this embodiment, when separating the electrode 3 from the inside of the furnace 1, the front end of the electrode 3 is covered with the first glass plate 10, but the present invention is not limited thereto. Instead of the first glass plate 10 , for example, glass shavings may be used to cover the tip of the electrode 3 . The first glass plate 10 and glass cullets are preferably those made of the same composition system as the molten glass 2 produced by melting the glass raw material 4 , more preferably the glass plates and glass cullets having the same composition as the molten glass 2 .

Furthermore, the opening 5ba of the upstream side end part 5b of the pipe 5 is covered with the 2nd glass plate 11 and the 3rd glass plate 12 which are glass materials before the start of a 1st temperature raising process. In this way, the inside of the tube 5 and the inside of the furnace 1 are separated by the two glass plates 11 and 12 . The state in which the inside of the tube 5 is separated from the inside of the furnace 1 continues until both the glass plates 11 and 12 are melted as the temperature in the furnace 1 rises. Thereby, during the period from the start of the first heating step to the melting of the two glass plates 11, 12, the communication between the gas in the furnace 1 and the tube 5 is prevented, and the contact between the oxygen-containing ambient gas in the furnace 1 and the inner peripheral surface 5a of the tube 5 is prevented. In this way, oxidation of platinum constituting the inner peripheral surface 5 a of the tube 5 is avoided as much as possible. When molten glass 2 is non-alkali glass, it is preferable to use the glass plate containing non-alkali glass for both glass plates 11 and 12 .

Hereinafter, a specific form in which the second glass plate 11 and the third glass plate 12 are provided will be described with reference to FIG. 4 . In this embodiment, a case where the channel cross section of the tube 5 is rectangular will be described as an example. Of course, the present invention can also be applied even when the flow path cross section of the tube 5 is formed in a shape other than a rectangle, for example, a circle, an ellipse, or a polygon.

As shown in FIG. 4 , one second glass plate 11 is provided, and two third glass plates 12 are provided to clamp the second glass plate 11 . In this embodiment, both glass plates 11, 12 have a rectangular shape.

The second glass plate 11 is installed in a state standing upright from the upstream end portion 5 b of the pipe 5 (rear wall 1 b of the furnace 1 ). The main surfaces (front and back) of the second glass plate 11 are in an inclined state with respect to the vertical line. The width dimension (the width dimension along the horizontal direction) of the second glass plate 11 is the same dimension as the width dimension of the tube 5 . The upper edge part of the 2nd glass plate 11 is located above the upper part of the upstream side end part 5b. On the other hand, the lower side of the second glass plate 11 is in contact with the bottom wall 1f of the furnace 1 .

The two third glass plates 12 are respectively installed in an upright state in a substantially upright posture so that their main surfaces are in contact with the end faces in the width direction of the second glass plate 11 . The upper edge portions of the third glass plates 12 are located above the upper portion of the upstream end portion 5b. On the other hand, the lower side of the third glass plate 12 is in contact with the bottom wall 1f of the furnace 1 . One of a pair of side portions extending in the vertical direction of the third glass plate 12 is in contact with the rear wall 1 b of the furnace 1 .

Although not shown in the figure, it is preferable to include a gap formed between the widthwise end surface of the second glass plate 11 and the main surface of the third glass plate 12, and the gap leading from the furnace 1 to the inside of the tube 5 is blocked with a glass sheet or glass shavings as a glass material. Furthermore, these gaps are required to be as small as possible, so they can also be blocked by the glass raw material 4, but from the viewpoint of avoiding the possibility of part of the components of the raw material 4 volatilizing before melting, it is preferable to use a glass material. In addition, the surface shape of the 2nd glass plate 11 and the 3rd glass plate 12 may be trapezoidal or triangular, for example other than rectangle, and the glass plate with a different surface shape may be used together.

Furthermore, in the present embodiment, the outer peripheral surface of the upstream end portion 5b is in a state of being in contact with the rear wall 1b without being exposed to the atmosphere in the furnace 1, but the outer peripheral surface of the upstream end portion 5b may be exposed to the atmosphere in the furnace 1. In this case, the outer peripheral surface of the upstream end portion 5b may also be included. During the execution of the continuous production step, the entire portion of the tube 5 in contact with the molten glass 2 (parts made of platinum or a platinum alloy) may be covered with glass shavings, glass plates, glass plates, glass raw materials 4, and the like. For example, the upper surface of the outer peripheral surface of the upstream end portion 5 b may be covered with a glass plate, and the side surfaces of the outer peripheral surface of the upstream end portion 5 b may be covered with the two third glass plates 12 . Furthermore, the inner peripheral surface 5 a of the tube 5 may be covered with the glass frit 4 filled in the tube 5 .

Here, in this embodiment, the front end of the electrode 3 is covered with the first glass plate 10, and the opening 5ba of the upstream end portion 5b is covered with the second glass plate 11 and the third glass plate 12 before the first temperature raising step is started, but the present invention is not limited thereto, and these operations may be performed at the beginning of the first temperature raising step.

As described above, after the preparations for executing the start-up step are completed, then, as shown in FIG. 3 , the first temperature raising step is started by operating the air burner 7 to spray the flame 7a. Furthermore, in this embodiment, when the first temperature raising step is started, the supply of the glass raw material 4 into the furnace 1 is not started, and the molten glass 2 and the glass raw material 4 are not present in the furnace 1 except for glass sheets or glass shavings that block the gap between the first to third glass plates 10, 11, 12 and the two glass plates 11, 12.

When the temperature in the furnace 1 (ambient air temperature of the ceiling wall 1e) rises to any temperature in the range of 700°C to 900°C after the first temperature increase step starts, as shown in FIG. 5, switching from the first temperature increase step to the second temperature increase step is performed. For example, the operation of the air burner 7 is sequentially stopped, and the operation of the oxygen burner 8 is sequentially started. The start of the operation of the first oxygen burner 8 is the start of the second temperature raising step.

After switching from the first temperature raising step to the second temperature raising step, when the temperature in the furnace 1 rises to a temperature at which the glass raw material 4 can be melted (hereinafter referred to as a melting temperature), as shown in FIG. A part or all of the glass raw materials 4 may be glass cullets.

In addition, the raw material supply starting step may be performed simultaneously with the completion of switching from the first temperature raising step to the second temperature raising step as long as the temperature in the furnace 1 rises to the meltable temperature. On the other hand, the raw material supply start step may be performed at any time before the temperature in the furnace 1 rises to the melting temperature. However, from the viewpoint of avoiding the possibility that the components contained in the glass raw material 4 evaporate and disappear before the raw material 4 is melted, it is preferable to perform the raw material supply start step after the temperature in the furnace 1 rises to the melting temperature.

After the raw material supply start step, as shown in FIG. 7 , the glass raw materials 4 supplied into the furnace 1 are sequentially melted, and the molten glass 2 is stored in the furnace 1 . Thereby, the height position of the surface 2a of the molten glass 2 rises gradually in the furnace 1. Furthermore, as shown by the two-dot dash line in FIG. 7 , the first glass plate 10 separating the inside of the furnace 1 from the electrode 3, the second glass plate 11 and the third glass plate 12 separating the inside of the furnace 1 from the inside of the tube 5 melt sequentially as the temperature in the furnace 1 rises.

And after the height position of the surface 2a of the molten glass 2 reaches a predetermined reference position, as shown in FIG. 8, the electrode 3 is moved from a retracted position to an advancing position. And, the electric heating start step is performed by applying a voltage to the electrode 3 . The temperature in the furnace 1 (molten glass) at this time exists in the range of 1300 degreeC - 1600 degreeC, for example.

Then, as shown in FIG. 9, when the height position of the surface 2a of the molten glass 2 reaches the position when the continuous production step is performed, and the temperature in the furnace 1 becomes substantially uniform at the operating temperature, the operation of the oxygen burner 8 is sequentially stopped in order to maintain the temperature in the furnace 1. The start-up procedure ends when all oxygen burners 8 are out of operation. Then, in the furnace 1 the continuous generation step is started.

Hereinafter, the main function and effect of the manufacturing method of the glass article which concerns on embodiment of this invention are demonstrated.

In the method for manufacturing a glass article according to the first embodiment, in the first and second temperature raising steps, heating is performed by the air burner 7 or the oxygen burner 8 in a state where the contact between the ambient air in the furnace 1 and the inner peripheral surface 5a of the pipe 5 is prevented by both glass plates 11 and 12, and the temperature in the furnace 1 is raised from normal temperature. Thereby, the ambient air in the furnace 1 containing oxygen sent into the furnace 1 accompanying the use of both burners 7 and 8 can be prevented from flowing into the pipe 5 . As a result, oxidation or volatilization of platinum or a platinum alloy constituting the inner peripheral surface 5 a of the tube 5 can be suppressed as much as possible.

<Second Embodiment> Hereinafter, with reference to FIG. 10, the manufacturing method of the glass article which concerns on 2nd Embodiment of this invention is demonstrated. In addition, in the description of the second embodiment, overlapping descriptions will be omitted by attaching the same reference numerals to elements substantially the same as those already described in the first embodiment, and only differences from the first embodiment will be described.

The second embodiment differs from the above-mentioned first embodiment in that the furnace 1 is used as a first glass melting furnace 13 (hereinafter referred to as a first furnace 13 ), and the pipe 5 is used as a first pipe 14 , and the first furnace 13 is connected via the first pipe 14 to a second glass melting furnace 15 (hereinafter referred to as a second furnace 15 ) into which molten glass 2 flowing out of the first furnace 13 flows. The second furnace 15 has the same structure as the first furnace 13 except that the screw feeder 6 is not provided. In addition, the first pipe 14 of the present embodiment is arranged in a horizontal posture in the longitudinal direction, but may also be arranged in an inclined posture in the longitudinal direction so as to increase in height as the distance from the first furnace 13 increases. In addition, in this embodiment, the bottom wall 1f of the first furnace 13 and the bottom wall 1f of the second furnace 15 have the same height, but the bottom wall 1f of the second furnace 15 may be arranged at a higher position than the bottom wall 1f of the first furnace 13, or the bottom wall 1f of the second furnace 15 may be arranged at a lower position than the bottom wall 1f of the first furnace 13.

Also in the second furnace 15, the first and second temperature raising steps of raising the temperature inside the second furnace 15 from normal temperature by the air burner 7 or the oxygen burner 8 are performed. In this embodiment, the first and second temperature raising steps of the second furnace 15 are executed simultaneously with the execution of the first and second temperature raising steps in the first furnace 13, but they do not necessarily need to be started at the same time or executed synchronously, and there may be some time lag. The first and second temperature raising steps in the second furnace 15 can be performed under the same conditions as the first and second temperature raising steps in the first furnace 13 .

In the first and second heating steps in the second furnace 15, the opening 5ca of the downstream end portion 5c in the first pipe 14 may not be covered with a glass plate, but in order to further prevent the ambient air in the second furnace 15 from contacting the inner peripheral surface 5a of the first pipe 14, as shown in FIG. The form of the opening 5ca covering the downstream end portion 5c is the same as the form of the opening 5ba covering the upstream end portion 5b.

In addition, in the first and second temperature raising steps in the second furnace 15, the ambient air in the second furnace 15 is prevented from contacting the inner peripheral surface 5a of the second pipe 16 as a second outflow passage for letting the molten glass 2 flow out of the second furnace 15. For this reason, the opening 5ba of the upstream side end part 5b of the 2nd pipe 16 is covered with the 2nd glass plate 11 and the 3rd glass plate 12 which are glass materials. The form covering the opening 5ba of the upstream end portion 5b in the second pipe 16 is the same as the form covering the opening 5ba of the upstream end portion 5b in the first pipe 14 .

In addition, this invention is not limited to the structure of the said embodiment, nor is it limited to the said operation effect. Various modifications can be made in the present invention without departing from the scope of the present invention.

In the said embodiment, molten glass was continuously produced only by the heating of the electrode 3 in a continuous production process, but it is not limited to this, You may use together the heating of the burner 7,8. In addition, in the continuous production step when the glass melting furnace is constituted by the first furnace 13 and the second furnace 15 as in the second embodiment, heating by the electrodes 3 and heating by the burners 7 and 8 may be used in combination in the first furnace 13, and only heating by the burners 7 and 8 may be used in the second furnace 15. In the case of heating using the burners 7, 8 in the continuous production steps, it is preferable to use the oxygen burner 8. From the viewpoint of reducing the β-OH value of the glass product to be produced, it is preferable to use a single melting furnace 1 and continuously produce molten glass only by heating by the electrodes 3 in the continuous production step as in the first embodiment.

1: Glass melting furnace 1a: front wall 1aa: opening 1b: rear wall 1c, 1d: side walls 1e: top wall 1f: bottom wall 2: Molten glass 2a: Surface 3: electrode 4: glass raw material 5: tube 5a: inner peripheral surface 5b: Upstream end 5ba, 5ca: opening 5c: Downstream end 6: Screw feeder 7: Air burner 7a, 8a: flame 8: Oxygen burner 9: Burner pair 10: First glass plate 11: Second glass plate 12: The third glass plate 13: The first glass melting furnace 14: First Tube 15: The second glass melting furnace 16: Second pipe T: flow direction

Fig. 1 is a longitudinal sectional view showing a continuous production step in a method for manufacturing a glass article according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view showing a continuous production step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 3 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 4 is a perspective view showing a start-up step in the method of manufacturing a glass article according to the first embodiment of the present invention. Fig. 5 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 6 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 7 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 8 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 9 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the first embodiment of the present invention. Fig. 10 is a longitudinal sectional view showing a start-up step in the method for manufacturing a glass article according to the second embodiment of the present invention.

1: Glass melting furnace

1b: rear wall

1c: side wall

1f: bottom wall

5: tube

5a: inner peripheral surface

5b: Upstream end

5ba: opening

11: Second glass plate

12: The third glass plate

Claims (8)

A method for manufacturing a glass article, comprising: a continuous production step of continuously supplying glass raw materials to molten glass stored in a glass melting furnace, melting the glass raw materials to continuously produce new molten glass, and causing the molten glass to flow out of the glass melting furnace through an outflow passage having an inner peripheral surface made of platinum or a platinum alloy; a temperature raising step in which the temperature in the glass melting furnace is raised from normal temperature; and a raw material supply start step in which the glass raw material is started to be supplied into the glass melting furnace, wherein in the temperature raising step, heating is performed by the burner to suppress oxidation or volatilization of platinum or a platinum alloy on the inner peripheral surface of the outflow passage while reducing the contact between the ambient air in the glass melting furnace and the inner peripheral surface of the outflow passage. In the method for manufacturing a glass article as described in Claim 1, a masking material is used to prevent the ambient air in the glass melting furnace from contacting the inner peripheral surface of the outflow passage. The method for manufacturing a glass article according to claim 2, wherein a glass material is used as the masking material. The method of manufacturing a glass article according to claim 3, wherein a glass plate covering an opening at an upstream end portion of the outflow passage is used as the glass material. Manufacture of glass articles as described in claim 3 or 4 The method, wherein the composition of the glass material is the same as that of the molten glass. The glass melting furnace according to any one of claims 1 to 4 of the patent application, wherein the glass melting furnace includes an electrode that can move between an entry position into the furnace and a retreat position retreating from the furnace, in the continuous generation step, the electrode at the entry position is energized and heated, and in the temperature raising step, the ambient air in the glass melting furnace is prevented from contacting the electrode by covering the front end of the electrode at the retreat position with a cover member. The method for manufacturing glass articles according to any one of claims 1 to 4 of the patent claims, wherein the glass melting furnace is used as a first glass melting furnace, and the outflow passage is used as a first outflow passage, and the first glass melting furnace is connected to a second glass melting furnace through the first outflow passage, into which molten glass flowing out of the first glass melting furnace flows into, and in the second glass melting furnace, a temperature raising step of using a burner to raise the temperature inside the second glass melting furnace from normal temperature is performed, and in the second glass melting In the temperature raising step in the melting furnace, heating is performed by the burner in a state where the ambient air in the second glass melting furnace is prevented from contacting the inner peripheral surface of the first outflow passage by the shielding material, and the ambient air in the second glass melting furnace is prevented from contacting the inner peripheral surface made of platinum or a platinum alloy in the second outflow passage for letting molten glass flow out of the second glass melting furnace. The glass object described in any one of the first to fourth items of the scope of the patent application A method for producing a product, wherein in the continuous production step, the molten glass stored in the glass melting furnace is heated only by electric heating.