JP2003089528A - Method for melting glass, equipment for melting the same, and method for manufacturing glass formed article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for melting glass for manufacturing many and diversified kinds of glass products with good productivity with a smaller number of facilities and an equipment for melting glass using the method. SOLUTION: The method for melting the glass comprises making molten glass from glass raw materials in a melting vessel 1, then retransferring the entire volume thereof into an accumulating vessel, thereafter putting the melting vessel 1 and the accumulating vessel into a shut-off state, allowing next the molten glass to flow out into a forming process step and performing the operation to make the next molten glass in the melting vessel, and the melting equipment has the melting vessel 1 for melting, clarifying and homogenizing the glass raw materials, the accumulating vessel 2 for accumulating the molten glass obtained in the melting vessel 1, a connecting mechanism 3 capable of introducing and shutting off the molten glass from the melting vessel 1 to the accumulating vessel 2, and outflow mechanisms 4 and 5 for allowing the molten glass accumulated in the accumulating vessel 2 to flow out to the forming process step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass melting method, a melting apparatus therefor, a glass molded product manufacturing method, and an optical element manufacturing method. More specifically, the present invention relates to a glass melting method for producing a wide variety of glass products with high productivity with a small number of facilities, a glass melting apparatus used for the method, and a glass molded article to which the glass melting method is applied. The present invention relates to a method and a method for manufacturing an optical element.

[0002]

2. Description of the Related Art As a glass melting apparatus for making optical glass, a melting tank for melting glass raw materials, a fining tank for refining and removing bubbles in the molten glass, and stirring the clarified molten glass to make it more homogeneous. It is known that a plurality of containers are provided, such as a work tank that is sent to an outflow pipe after being converted. For example, in the apparatus disclosed in JP-A-58-41729, the volume of the melting tank is made larger than that of the other tanks in order to efficiently produce the optical glass having a constant refractive index by the continuous melting method. When the raw materials are put into the melting tank, the connection pipe between the melting tank and the fining tank is closed, and after the raw material feeding is stopped, the operation such as opening the connection pipe between the melting tank and the fining tank is performed. There is.

By the way, in recent years, in order to meet various demands such as lenses for cameras, digital cameras, video cameras, parts for optical communication, etc., a wide variety of optical glasses and diversification of shapes of optical elements are progressing. Product development cycles have also been shortened, and demand for shorter delivery times is increasing. Although the equipment in the above publication is excellent as equipment for producing an optical glass having a stable refractive index, it has the following problems in producing a glass product in a small lot of multiple glass types.
That is, in order to prevent mixing of different glass types when changing the glass type, all molten glass in each tank is discharged and washed,
The melting of the next glass type must be started. Therefore, while the molten glass is flowing out, the next glass type cannot be melted and a short delivery time cannot be achieved.

[0004]

SUMMARY OF THE INVENTION Under the circumstances, the present invention is directed to a glass melting method and a glass melting apparatus used for manufacturing a glass product of various types with a small number of facilities with high productivity. Another object of the present invention is to provide a method for manufacturing a glass molded product and a method for manufacturing an optical element, to which the glass melting method is applied.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the inventors of the present invention can achieve the object by a specific glass melting method and a specific glass melting device. The present invention has been completed based on this finding.

That is, according to the present invention, (1) a molten glass is produced from a glass raw material in a melting tank, and then the whole amount is transferred to a storage tank, and then the melting tank and the storage tank are shut off from each other, and the storage tank is closed. While flowing out the molten glass in the forming step, the glass melting method, characterized in that the operation of producing the next molten glass in the melting tank is performed,

(2) Melting and refining glass raw materials in a melting tank
Melting step to make molten glass by homogenization, after transferring the total amount of molten glass in the melting tank to the accumulation tank, a transfer step of blocking the inflow of molten glass from the melting tank to the accumulation tank, the accumulation tank The glass melting method according to the above item (1), which includes an outflow step of outflowing the molten glass in the molding step to the forming step, and further performs the following melting step in parallel with the outflow step after the transfer step. The glass melting method according to the above item (2), wherein the molten glass produced in the melting step before and after the transfer step is a different glass.

(4) In a glass melting apparatus for melting a glass raw material to produce a molten glass for producing a glass molded article, a melting tank for melting, refining and homogenizing the glass raw material, and A storage tank for storing the molten glass, a connection mechanism capable of introducing and blocking the molten glass from the melting tank to the storage tank, and an outflow mechanism for flowing the molten glass accumulated in the storage tank to the molding step. (5) The glass melting device characterized by having (5) the storage tank has a capacity equal to or more than the capacity of the melting tank, and the height (m) / volume (m ³ ) ratio is 1 to 5 The glass melting apparatus according to the item,
(6) A method for producing a glass molded article, which comprises molding a molten glass flowing out by the glass melting method according to the above (1), (2) or (3),

(7) When manufacturing a glass molded article using a molding die, the time required for the outflow process is shorter than the time required for the melting process, and after the outflow process, the molding die is replaced to have a different shape. (6) for producing a glass molded article of
Item 8. A method for producing a glass molded article according to item (8), and (8) performing press molding by the method according to item (6) or (7) above to obtain an optical element blank, followed by grinding and polishing. A method of manufacturing a featured optical element is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the glass melting method of the present invention, a molten glass is produced from a glass raw material in a melting tank, and then the whole amount is transferred to an accumulation tank, and then the melting tank and the accumulation tank are shut off. In this state, the molten glass in the accumulating tank is caused to flow out to the forming step, and an operation of producing the next molten glass in the melting tank is performed.

Specifically, the glass raw material is melted in a melting tank,
Clarification, a melting step of producing a molten glass by homogenization, after transferring the total amount of molten glass in the melting tank to the accumulation tank,
Performing a transfer step of blocking the inflow of molten glass from the melting tank to the accumulation tank, and an outflow step of flowing out the molten glass in the accumulation tank to the molding step, and after the transfer step,
The following dissolution step is performed in parallel with the outflow step.

The glass melting apparatus of the present invention used in this glass melting method melts, clarifies, and melts glass raw materials.
A homogenizing melting tank, a storage tank for accumulating the molten glass obtained in the melting tank, a connection mechanism capable of introducing and blocking molten glass from the melting tank to the accumulating tank, and accumulating in the accumulation tank. And an outflow mechanism for outflowing the molten glass to the forming step.

Next, the glass melting method of the present invention and the glass melting apparatus of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view of an example of a glass melting apparatus of the present invention. This apparatus is connected to a melting tank 1, a storage tank 2 and a bottom of the melting tank as main components, and a molten glass in the melting tank is provided. Connecting pipe 3 (connecting mechanism) for guiding the
It has a working tank 4 equipped with a stirrer for further homogenizing the molten glass flowing from the storage tank, and an outflow pipe 5 attached to the lower portion of the working tank for discharging the molten glass. It is desirable to use platinum or a platinum alloy for the flow path of molten glass including the melting tank 1, the accumulation tank 2, the connecting pipe 3, the working tank 4, and the outflow pipe 5, and the accumulation portion.

The melting tank 1 melts the glass raw material and
It is a container that also performs clarification, and has a function of heating the contents of the container to a relatively high temperature of about 1400 ° C. As the material, it is preferable to use reinforced platinum in consideration of heat resistance. Examples of the strengthened platinum include platinum alloys containing zirconia, but are not limited to such alloys. The molten glass in the melting tank 1 is stirred by a stirrer 6. The glass raw material to be melted in the melting tank 1 may be a powdery raw material prepared, or a glassy raw material that has been melted in advance outside the melting tank 1 may be used.

The connecting pipe 3 is an industrial platinum pipe, one end of which is attached to the bottom of the melting tank, and the other end of which is arranged to discharge the glass to a molten glass receiving tank 7 connected to one end of the accumulating tank 2. There is. A known method can be appropriately used to control the glass flow in the connecting pipe 3,
It is desirable to use the following method. When electricity is applied to the connecting pipe 3 equipped with an energizing mechanism, the connecting pipe 3 generates heat,
Directly heat the glass in the pipe. When the flow of the molten glass is stopped by the connecting pipe 3, the connecting pipe 3 is turned off. Then, the temperature of the connecting pipe 3 is immediately lowered, the viscosity of the glass in the pipe is increased, and the flow is stopped. When resuming the flow of glass, the energization of the connecting pipe may be resumed. Such direct electric heating has a higher energy efficiency and can control the glass flow with a high response as compared with the indirect heating in which a heating element is provided around the connecting pipe for heating. Indirect heating may be appropriately used in combination with direct current heating.

The flow of molten glass in the melting tank is blocked by the above mechanism so that the molten glass does not flow into the accumulation tank at least during the melting process. The device includes a movable drain chute 8. This drain chute is for discharging the molten glass in the melting tank to the accumulation tank, and then discharging the residue made of the molten glass in the melting tank and the connecting portion, which has been washed out. For example, a gutter-shaped metal plate can be used as the drain chute 8. By inserting the drain chute 8 between the connection pipe 3 and the molten glass receiving tank 7 (transfer path) after transferring the molten glass, the effluent from the connecting pipe does not flow into the molten glass receiving tank 7. , Can be led out of the device. The drain chute 8 is removed from the transfer path before the start of the molten glass transfer process.

The molten glass received in the molten glass receiving tank 7 is guided to the accumulating tank 3. The molten glass receiving tank 7 and the accumulating tank 3 can be made of an industrial platinum material like the connecting portion. The molten glass transferred into the storage tank is temperature-controlled and kept in a molten state so that the viscosity of the molten glass does not hinder stirring in the working tank, outflow from the outflow pipe, and molding. The capacity of the storage tank 3 needs to be able to store the entire amount of the molten glass obtained in the melting tank 1. for that reason,
It is preferable that the volume is equal to or larger than the volume of the dissolution tank. The capacity of the dissolution tank is preferably 10 to 100 liters. In the transfer process, the total amount of molten glass in the melting tank,
Transferred to storage tank.

In the transferring step, the molten glass flowing out from the connecting pipe 3 flows into the molten glass receiving tank 7, but at this time, the molten glass receiving tank 7 has a gutter-shaped platinum so that the molten glass flow does not entrap bubbles. Alternatively, it is preferable to place a guide plate 9 made of a platinum alloy, and to guide the molten glass flow flowing out from the connecting pipe 3 to the molten glass receiving tank 7 without bubbling with the guide plate. At this time, it is desirable to minimize the distance between the outlet of the connecting pipe 3 and the guide plate 9 in order to prevent foaming.

Due to the outflow of the molten glass, the liquid level of the molten glass in the accumulation tank is lowered. The outflow rate of the molten glass decreases in proportion to the height of the liquid level of the molten glass in the accumulation tank if the temperature of the outflow portion is kept constant. In forming the molten glass that flows out, it is desired that the outflow rate be kept constant, so it is desired to reduce the change in the liquid level of the molten glass. In order to meet such requirements, it is preferable that the storage tank has a flat shape with a low height. For example, the storage tank is advantageously shaped to have a height (m) / volume (m ³ ) ratio in the range of 1-5. An outflow pipe 5 for supplying molten glass to a forming apparatus is attached to the bottom of the work tank.

As mentioned above, the refining of the molten glass is carried out in the melting tank, so that the accumulating tank need not have a fining function. For refining, the molten glass must be heated to approximately 1350 to 1400 ° C.
It is sufficient to provide a heating device for keeping the temperature at 50 to 1150 ° C. Therefore, it is sufficient that the connecting pipe 3, the molten glass receiving tank 7, the storage tank 2, the pipe connecting the storage tank and the working tank 4, the working tank 4, and the outflow pipe 5 are made of industrial platinum,
No need to use expensive reinforced platinum.

Although the molten glass can be directly received in the storage tank 2 without installing the receiving tank 7, the molten glass is likely to be corroded, so that replacement workability and replacement cost in the case of corrosion are likely to occur. Therefore, it is preferable to install the receiving tank 7 having a small capacity.

In the present invention, the molten glass flowing out is molded in this manner to manufacture a desired glass molded product. At this time, the molding method is not particularly limited, and various methods are applied. be able to. Here, direct press molding, molding of a preform for press molding, and molding of plate glass, which are typical molding methods, will be described.

<Direct Molding> Direct press molding is a method in which an appropriate amount of molten glass is press-molded by a press mold while the glass is in a softened state to make a glass molded product. For example, a plurality of dies (lower dies of a press forming die) are arranged at equal intervals around a rotation axis of the table on a turntable that is index-rotated at a constant speed.
The turntable is installed so that the mold is located vertically below the outflow pipe while the turntable is stationary. The molten glass is supplied to the mold (referred to as casting) by cutting the molten glass flow flowing out from the outflow pipe with a cutting blade called shear, so that a desired amount of molten glass falls onto the mold. After casting, the die is transferred to the pressing position by index rotation, and is pressed there by the lower die and the upper die facing the lower die while the die is stopped. The molded product is transferred to the ejection position and ejected from the mold. The mold from which the molded product has been taken out is returned to the casting position again, and the above series of steps is repeated.

Lower mold and upper mold having the same shape (in some cases,
If the weight of the molten glass to be cast is kept constant by using a mold such as a barrel mold), glass molded products having the same shape can be continuously produced. The molded product taken out is conveyed to an annealing furnace, where the strain is removed while being gradually cooled.

Molding of one lot (a plurality of molded products of the same glass type and the same shape) is made by melting once, so that an integral multiple of the amount of molten glass made by melting once is consumed. It is preferable to schedule the production so that the molten glass is consumed. When the next 1 lot is a molded product having the same glass type or different glass type and different shapes, the die of the press machine is exchanged and adjusted during the next melting after the completion of 1 lot molding ( Method 1). Alternatively, prepare another press machine, set molds of different shapes on the press machine, or change the number of molds placed on the turntable to prepare for the next lot molding. After completion of the molding of the lot, the pressing machine may be replaced to mold a molded article having a different shape (method 2). However, it is more preferable to adjust the melting and molding schedules and produce the molded product by the method 1 in that one press machine is sufficient. For melting and molding schedule,
An example will be described.

In the case of producing a lens, a lens blank having a desired lens shape in which the allowance is taken into consideration is molded as described above, and the annealed blank is ground and polished to produce a lens. . In this way, various lenses such as a meniscus lens, a biconcave lens and a biconvex lens can be produced. If necessary, an optical thin film such as an antireflection film may be formed on the obtained optical element.

<Molding of Preform for Press Molding> In the direct press molding, a mold corresponding to the lower mold of the press mold was arranged on the turntable and press molding was performed. , A receiving mold having a gas outlet at the bottom is arranged, an appropriate amount of molten glass flowing out is received by the receiving mold, nitrogen gas or air is ejected from the gas outlet, and the glass sphere is rotated while rotating the molten glass. Mold.

This glass sphere is used as a preform for press molding when precision press molding (so-called mold optics molding) is performed without grinding or polishing an optical element such as an aspherical lens. Therefore, the weight of each piece must be precisely set, the outflow pipe (outflow nozzle) through which the molten glass flows out is also precisely processed, and the temperature of the nozzle is also precisely adjusted.

Also in the molding of such a preform, it is preferable to carry out the work for the molding of the next lot after the molding of one lot is completed, as in the direct press molding. The preform thus obtained is reheated,
Precision press molding is performed in a nitrogen gas atmosphere and processed into molded products such as aspherical lenses.

<Molding of glass plate> A molten glass which continuously flows out from an outflow pipe at a constant speed is cast into a mold, and the cooled glass is slowly drawn out at a constant speed from the open end of the mold to obtain a plate having a constant thickness and width. Shape glass.
The plate glass is passed through the annealing furnace as it is, and the strain is removed. After that, the plate-shaped glass is cut and divided into a diced shape, and processed into glass pieces called cut pieces. The cut piece is barrel-polished to produce a roughened glass gob of a certain weight. This glass gob is reheated and press-molded to be an optical element blank such as a lens blank. The blank is subjected to grinding and polishing to finish various lenses.

In the method for producing a glass molded article of the present invention, the molten glass flowing out by the above-described glass melting method of the present invention is molded by the various molding methods described above to produce a glass molded article. When manufacturing a glass molded product using, the time required for the outflow process is made shorter than the time required for the melting process, and after the outflow process, the molding die is replaced to manufacture a glass molded product having an irregular shape. Is advantageous.

[0032]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example Glass was melted by the glass melting apparatus shown in FIG.
FIG. 2 shows an operation form showing the order of the melting step, the transferring step and the outflow step. In FIG. 2, the upper diagram labeled MZ indicates the melting process, the middle diagram labeled MZ + PZ + WZ indicates the transfer process, and the lower diagram labeled PZ + WZ indicates the outflow process. The dissolution step is 18 hours, the transfer step is 5.5 hours, the outflow step is 15 hours, and the time required from the dissolution step to the outflow step is 38.5 hours. However, the feature of the present embodiment is that after the transfer step, the next melting step is started, and the molten glass necessary for forming one lot can be supplied with 20.5 hours as one cycle. . Upon completion of the transfer process, the melting process, the outflow process, and the molding process are started at the same time (which can be regarded as simultaneous compared to the length of each process), and when the outflow process and the molding process are completed after 15 hours, Set and adjust the molding machine such as mold replacement. The melting step is performed even when setting and adjusting the molding machine, and it is not necessary to wait for a series of steps from melting of glass to molding. It should be noted that during the transfer process 2.5 hours, the melting tank and the connecting portion were washed, and the molten glass receiving tank, accumulating tank, working tank,
The outflow pipe and the pipe connecting the above-mentioned parts are cleaned. In this embodiment, the melting tank has a capacity of 40 liters and the accumulation tank has a capacity of 50 liters.

In this way, the cycle of melting and molding different kinds of glass could be sequentially performed for 20.5 hours without waiting time. There was no variation in the optical characteristics of each lot, and it was exactly within the target range.

Glass moldings molded from molten glass are annealed to remove strain. In this annealing, glass molded products before annealing are put in from the high temperature side inlet of the furnace where a temperature gradient is provided, gradually cooled while transferring to the low temperature side in the furnace, and a plurality of molded products are output from the low temperature side outlet. A continuous annealing method capable of continuously annealing is preferable. In this embodiment, since there is 5.5 hours from the end of the molding of lot A to the start of the molding of the next lot B, the last molded product in lot A is better than the first molded product in lot B. Also proceeded in the annealing furnace for 5.5 hours. The annealing time is shorter than 5.5 hours, and if the annealing temperature of the lot B is set to the annealing temperature of the lot B after the annealing of the lot A is completed,
Even if the annealing temperatures of lots A and B are different, it is not necessary to suspend the annealing of lot B and adjust the temperature of the furnace. If the annealing time is longer than 5.5 hours, the temperature inside the annealing furnace is divided into several temperature zones and the temperature is set for each zone. You can start the configuration. Of course, even when the annealing time is 5.5 hours or less, an annealing furnace whose temperature can be adjusted for each zone may be used. In this way, since the annealing temperature can be set by utilizing the time of the transfer process, the efficiency can be improved.

The outflowing molten glass was molded by the above-mentioned direct press molding method to obtain a meniscus lens blank.
A lot was prepared. Next, during the transfer process, preparations for changing the glass type were made, and upon completion of the transfer process, dissolution of different glass types was started. With this glass type, one lot of biconcave lens blank was prepared. After annealing, each lot was subjected to grinding and polishing to produce a meniscus lens and a biconcave lens.

As described above, it is possible to produce a plurality of lots in a short time by using one facility as compared with the conventional one. In this embodiment, direct press molding has been described as an example,
The present invention includes preform molding, plate glass molding,
It can also be applied to other molding methods.

[0037]

According to the present invention, it is possible to provide a glass melting method and a glass melting apparatus used therefor for producing glass products of various kinds with high productivity with a small number of facilities. Further, by applying the above-described glass melting method and glass melting apparatus, it is possible to manufacture glass molded articles such as optical elements of various types with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of a glass melting apparatus of the present invention.

FIG. 2 is a melting step in the glass melting method of the present invention,
It is an operation form figure showing the order of a transfer process and an outflow process.

[Explanation of symbols]

1 melting tank 2 storage tanks 3 connecting pipes 4 working tanks 5 Outflow pipe 6 stirrer 7 Molten glass receiving tank 8 drain shoot 9 Information board

Claims (8)

[Claims] 1. A step of forming molten glass from a glass raw material in a melting tank, transferring the whole amount to a storage tank, and then disconnecting the melting tank from the storage tank to form a molten glass in the storage tank. The method for melting glass is characterized in that the operation for producing the next molten glass is performed in the melting tank while flowing out to the glass. 2. A melting step of melting, refining and homogenizing a glass raw material in a melting tank to produce molten glass, and transferring all the molten glass in the melting tank to a storage tank, and then from the melting tank to the storage tank. A transfer step of blocking the inflow of the molten glass, and an outflow step of outflowing the molten glass in the accumulation tank to the forming step, and after the transfer step, the next melting step is performed in parallel with the outflow step. Item 2. The method for melting glass according to Item 1. 3. The glass melting method according to claim 2, wherein the molten glass produced in the melting step before and after the transferring step is a different kind of glass. 4. A melting vessel for melting, refining and homogenizing a glass raw material in a glass melting apparatus for melting a glass raw material to produce a molten glass for producing a glass molded article,
An accumulation tank for accumulating the molten glass obtained in the melting tank,
A glass melting apparatus comprising: a connection mechanism capable of introducing and blocking molten glass from the melting tank to the accumulation tank, and an outflow mechanism for flowing out the molten glass accumulated in the accumulation tank to a forming step. 5. The glass melting apparatus according to claim 4, wherein the storage tank has a capacity equal to or larger than the capacity of the melting tank, and the height (m) / volume (m ³ ) ratio is 1 to 5. 6. A method for producing a glass molded article, which comprises molding a molten glass flowing out by the glass melting method according to claim 1, 2 or 3. 7. When manufacturing a glass molded article using a molding die, the time required for the outflow step is shorter than the time required for the melting step, and after the outflow step, the molding die is replaced to change the shape. The method for producing a glass molded article according to claim 6, wherein a glass molded article is produced. 8. A method of manufacturing an optical element, which comprises performing press molding by the method according to claim 6 or 7 to obtain an optical element blank, and then performing grinding and polishing treatments.