JPS63295443A - Structure of outflow part for fused glass - Google Patents

Abstract

PURPOSE:To obtain an outflow part of fused glass which is simple, precise and capable of allowing it to intermittently flow out therethrough by providing an outflow controlling means for adjusting the pressure of gas which is brought into contact with fused glass between the connecting part of a storage tank of fused glass and the tip of the outflow part thereof. CONSTITUTION:The raw material of optical glass is introduced into a storage tank 2 of fused glass and heated with a temp. controlling means 4 to obtain fused optical glass G. Then this glass G is allowed to flow to a first-dthird parts 6a-6c having required cross-sectional areas and heated with the temp. controlling means 8, 10, 12 to adjust it at required viscosity and allowed to successively flow. On the other hand, the pressure of inert gas such as gaseous nitrogen introduced into a pipe 20a is changed with an outflow controlling means 20 consisting of a piston 20e and a bellows 20c or the like and the pressure exerted to glass G in corporated in the second part 6b is adjusted and thereby glass (g) having about logeta=4 viscosity is flowed out intermittently (e.g. interval of 15-60sec) through an outflow port 14 at every required volume (e.g. 5cm<3>).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the structure of a molten glass outflow section, and more particularly to the structure of a molten glass outflow section capable of precise intermittent outflow of molten glass. Such a structure is suitably used, for example, to flow molten optical glass to an optical element molding apparatus.

[Prior art and its problems] Conventionally, a blank for manufacturing an optical element is obtained [first,
The optical glass raw material is melted in a melting tank (crucible), the molten glass is flowed out from the outlet of the crucible at an appropriate flow rate, and the flowed glass is divided into blocks of appropriate size and placed in a molding bag. Continuous blank manufacturing is carried out in which blanks are supplied and press-formed into a predetermined shape.

In such continuous manufacturing methods, the supply of molten glass must be strictly and appropriately controlled in order to maintain constant molding conditions on the molding equipment side and perform continuous molding operations smoothly, as well as to maintain good molding accuracy. It is preferable to do so.

Furthermore, recently, instead of the traditional method of manufacturing a blank as described above and then polishing the blank to form an optical surface to obtain an optical element, melting in a mold with a predetermined surface accuracy has been used. It has become possible to immediately form the overall shape, including the optical functional surface, by housing and pressing optical glass, and it is necessary to supply molten optical glass to continuously perform such press forming. In this case, it is required to supply the molten glass more strictly and accurately than in the case of blank manufacturing.

For this reason, conventionally, the outflow section through which the molten glass flows out from the crucible is formed into a relatively long pipe shape, and a temperature control means (heating means) is attached around the outflow section.

By controlling the temperature of the molten glass in the outflow section, the viscosity of the glass is adjusted, thereby allowing molten glass of a desired viscosity to flow out from the outflow end at a controlled flow rate.

FIG. 3 is a sectional view showing an example of such a conventional molten glass outlet structure.

In FIG. 3, 2 is a molten glass storage tank, and around the tank there is a temperature side 91 means for melting the glass and keeping it warm.
A heating means (4) having a calorific value adjusting means is attached.

An outflow section 6 is connected to the lower part of the molten glass storage tank 2. The outflow section consists of a vertically elongated pipe, and temperature control means 8,
10°12 is attached. These temperature control means can each independently adjust the temperature. Note that 14 is an outlet at the lowest end of the outlet. On the other hand, a plunger 15 is arranged inside the molten glass storage tank 2. The plunger is reciprocated in the vertical direction by a driving means (not shown).

The glass G melted in the molten glass storage tank 2 flows downward in the outflow part 6 due to its own weight, and flows out [114 to g
It flows out as. At this time, the temperature control means 8, 10.
12 to appropriate temperatures, an appropriate temperature gradient is applied to the molten glass from the connection end with the molten glass storage tank 2 to the outlet 14, thereby controlling the flow rate and viscosity of the molten glass. be done. Further, by reciprocating the plunger 15 in the vertical direction at an appropriate period, the amount of glass flowing out is adjusted.

However, in the conventional outlet structure as described above, it is necessary to increase the length of the outlet part 6 considerably in order to create a desired temperature gradient, which has the disadvantage of increasing the space of the apparatus. That is, if the length of the flow ridge portion 6 is short, the set temperature gradient will be impaired due to heat conduction due to the flow of molten glass within the flow portion.

JP-A-61-146721 discloses a structure of a flowing mountain portion in which the diameter on the side of the connection end with the molten glass storage tank is relatively large and the diameter on the side of the outlet side is relatively small. Such a structure is also similar to the above.

Furthermore, since the outflow portion is long, the action of the plunger 15 does not reach upward to the outflow port 14, making it difficult to properly regulate the flow rate.

Therefore, the conventional glass outflow part structure cannot satisfy the desired outflow conditions, and therefore, press forming must be performed while controlling the molten glass to suit the outflow condition.

On the other hand, in order to maintain the operation of the plunger 15 under high temperatures, the strength and precision of the driving part must be sufficiently increased, and therefore the entire device must be considerably larger.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a molten glass outflow section structure that has a relatively simple configuration and is capable of precise intermittent outflow.

[Means for Solving the Problems] According to the present invention, in order to achieve the above-mentioned objects, in the structure of the outflow part for flowing out molten glass from the molten glass storage tank, the storage tank connection part and the outflow tip part are provided. A structure of a molten glass outflow section, characterized in that a flow ridge section (m) means is provided between the molten glass and the molten glass to bring the gas into contact with the gas and adjust the pressure of the gas.

is provided.

[Embodiment 1] Hereinafter, a specific embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of a molten glass outlet structure according to the present invention.

In FIG. 1, 2 is a molten glass storage tank, and a temperature control means 4 is attached around the tank. These molten glass storage tank 2 and temperature control means 4 are the same as in the L distribution 3 diagram.

An outflow portion 6 is provided at the bottom of the molten glass storage tank 2 . The outflow portion consists of an upper first portion 6a, a central second portion 6b, and a lower third portion 6C.
The upper end of the third portion 6C serves as the connection portion with the molten glass storage tank 2, and the lower end of the third portion 6C serves as the outlet 14.

The L2 first portion 6a has a diameter of Ill and extends in the vertical direction, and the third portion 6C has a diameter of D3 and extends in the vertical direction.
The S2 portion 6b diagonally connects the first portion 6a and the third portion 6c. The second portion 6b is connected to the first portion 6a and the third portion 6b.
It has a considerably expanded shape compared to the portion 6C. Temperature control means 8. are provided around the first, second and third parts, respectively. to, 12 are attached. These temperature control means can each independently adjust the temperature.

Outflow control means 2G is attached to the second portion 6b. The means includes a pipe 20a having one end connected to the upper side of the second portion 6b, and a chamber 2 connected to the other end of the pipe.
0b, a bellows 20c provided in the chamber,
It includes an air cylinder 20d connected to the chamber 20b and a piston 20e connected to the air cylinder.

Next, the operation of this embodiment will be explained.

A raw material for optical glass is placed in the molten glass storage tank 2, and the raw material is heated by the temperature control means 4 and maintained for a predetermined period of time with appropriate stirring as necessary, thereby obtaining a molten optical glass G.

Next, the molten glass G is caused to flow down to the flowing mountain portion 6. In the outflow section, the molten glass is sequentially divided into a first part, a second part,
Proceed with the third part. The driving force for this progression is primarily gravity.

The molten glass first has a predetermined diameter D in the first portion 6a.
By narrowing down to I, the amount flowing into the outflow portion 6, that is, the amount flowing out from the molten glass storage tank 2 is set. Here, the glass temperature is maintained relatively low by the temperature control means 8, and is adjusted so that the viscosity of the glass is, for example, log η=3.5 to 6. Since the diameter DI of the first portion 6a is relatively small, the viscosity can be controlled sufficiently efficiently by the temperature control section, thereby creating 11 small nodes of the outflow amount.

The molten glass then flows into the second portion 6b.

This part has an expanded shape and has a cross-sectional area, for example, 2 to 18 times that of the first part 6a, so it has sufficient thermal VF. Heated to a higher temperature, for example, the temperature is such that the viscosity of glass is log η = 3 to 4.5! One verse is said. The standard temperature of the entire outlet part 6 is set by heating in this part, and as shown in the figure, tI
An inert gas such as nitrogen gas is introduced into the pipe 20a of the output control means by means not shown. And E
The inert gas also penetrates into one side of the second distribution section 6b. Therefore, the molten glass flows along the lower side of the second portion 6b toward the third all1 portion 6C. At this time, since the lower side of the second portion 6b is slanted, the molten glass flows well without introducing bubbles into the molten glass or making the molten glass non-uniform.

Next, the glass flows into the third portion 6C. This portion has the smallest diameter D3 (the cross-sectional area is, for example, 174 to 1/20 of the second portion 6b), and the temperature control means 12
For example, the viscosity of glass can be easily reduced by heating by logη
The temperature is adjusted so that the temperature is 2 to 4.5. here,
By setting a predetermined temperature, a predetermined viscosity required for the molten glass flowing out from the outlet 14 is set.

The diameter D3 of the third portion 6c is appropriately set depending on the required outflow glass diameter, and is, for example, 3 to 15 mm.

In this embodiment as described above, by moving the piston 20e of the outflow control means in the vertical direction, the pressure of the inert gas in the pipe 20a is changed via the bellows 20c, and thus the pressure in the second portion 6b is changed. The pressure applied to the glass can be adjusted. As a result, a pressure change effectively acts on the molten glass in the first part 6C, which has a lower viscosity than the molten glass in the first part 6a, and the amount of glass flowing out from the outlet 14 can be set appropriately. For example, when the piston 20e is moved upward, the pipe 20e
The pressure of the inert gas in a is reduced and the third part 6
The outflow of the molten glass in C can be temporarily stopped. When the piston 20e is then moved downward, the pressure of the inert gas within the pipe 20a is increased, and the molten glass can start flowing out from the third portion 6c.

Thus, by appropriately controlling the outflow control means 20, it is possible to intermittently cause the molten glass g of a desired viscosity to flow out from the outflow port 14 in desired volumes. Furthermore, since the diameter of the third portion 6c is small, the atmosphere will not enter into the RF43 portion 6C from the outlet 14 even while the outflow control means 20 is activated to reduce the pressure and stop the outflow.

According to this embodiment, since the expanded portion is formed as the second portion 6b of the outflow portion, the temperature of this portion is set to the reference temperature, and the temperatures of the first portion 6a and the third portion 6c are set to the reference temperature. Even if both the flow rate adjustment and the viscosity adjustment are performed by setting an appropriate temperature from the reference temperature, the first portion 6a and the third portion 6c will not interfere in temperature because the second portion 6b has a large heat capacity. Both the flow rate and the viscosity of the outflow glass can be very well controlled.

In this embodiment, the first part hot water temperature T (6a
), the second part hot water temperature T(6b) of the outflow part 6 and the third part hot water temperature T(6c) of the outflow part 6 are T(6a) <T(6b
) <T (6c), and a second portion 6b with a large cross-sectional area and a large capacity for molten glass is interposed between the first portion 6a having a low temperature and the third portion 6c having a high temperature. Therefore, the high temperature of the third portion 6C is not directly transmitted to the low temperature first portion 6a, and the amount of glass flowing out from the outlet 14 at the tip of the third portion can be accurately controlled. That is, in this embodiment, the temperature of the glass G in the molten glass storage tank 2 is high, and the temperature of the first portion 6a is lowered to control the glass flow after the first portion. Since the barrel second portion 6b is provided,
The temperature of the third part 6C is not directly transmitted to the first part 6a, and the temperature rise is suppressed by the glass in the second part 6b, so the temperature of the glass in the first part 6a does not rise. The glass passing through 6C flows as if pulling the glass in the second part 6C, and the glass in the second part flows as if pulling the glass in the first part 6a, so the amount of glass flowing out from the outlet 14 is ultimately depends on the viscosity of the glass in the first portion 6a. Therefore, it is extremely advantageous to prevent the temperature of the third portion 6C from interfering with the temperature of the first portion 6a due to the presence of the second portion 6b, which is an extension, for accurately controlling the amount of glass flowing out. be.

In addition, the outflow part 6 (diameter 10 mm, length 800 mm
mm), 12 cm3 of glass with viscosity logη=4
/min, but the diameter of the outflow part 6 (the diameter of the first part 6a and the diameter of the third part 6C of the first embodiment of the present invention was changed to 1/min).
0 mm, and the volume of the second portion 6b is approximately 5 mm of that of the third portion 6C.
), by operating the outflow control means 20, the absolute pressure inside the pipe 20a of said means is reduced to about 0.93 Kg/cm2 at appropriate time intervals and to about 1.1 Kg/cm2.
By alternating the pressure of /cm2, the viscosity lo
It was possible to intermittently flow out 5 cm of glass with gη = 4 at arbitrary intervals of 15 to 60 seconds.
Applicable to continuous press molding.

Figure 2 shows the second structure of the molten glass outlet due to unexploited Ill.
FIG.

In FIG. 2, the same members as in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, a heat insulating material 16 is disposed between the first part 6a and the second part 6b to prevent temperature interference, and the temperature interference is prevented between the second part 6b and the third part 6C. This differs from the first embodiment in that a heat insulating material 18 is disposed to prevent the above-mentioned. Furthermore, the shape of the second portion 6b differs from the first embodiment in that a temperature control means 22 is provided around the pipe 20a. The second embodiment is also different from the first embodiment in that .

In this embodiment, the glass in the second portion 6b always enters into the pipe 20a, and the temperature of the glass in this portion is controlled by the temperature control means 22. In this way, in this example, since the glass area that comes into contact with the inert gas is small,
Even in the case of glasses such as high-lead-containing glasses whose components volatilize from the surface in large quantities at high temperatures, the volatilization can be minimized, and defects caused by changes in refractive index can be prevented. In this embodiment, the heat insulating materials 16, 18 are placed above and below the 21st portion 6b, which is the extended portion L, and the temperature control means 8 of the first portion and the temperature control means lO of the second portion are arranged.
This is to prevent errors in temperature control due to convection and radiation between the third temperature control child stage 12 and the third part. That is, when the heat insulating material 16.18 is not arranged, each portion 6a,
If the lengths of 6b and 6C are shortened, the temperature control means will be placed quite close to each other, and there will be a difference in temperature between the temperature control means, so the temperature control means whose temperature is higher than that of temperature control means 8 Due to the heat of the temperature control element 1O, the air around the temperature control stage 1O flows toward the temperature control means 8 by convection, and this air temperature causes the temperature of the first portion 6a and the glass inside thereof to be controlled only by the temperature control means 8. The first portion 6a due to such convection and radiation effects tends to be difficult to control, and also tends to be difficult to control as the first portion 6a and the glass inside thereof are directly heated by the radiant heat of the temperature control means IO. The relationship between the second portion 6b and the second portion 6b is
The same applies between the portion 6b and the third portion 6c,
After all, each part 6a of the outflow part.

It becomes difficult to accurately control the temperatures of 6b and 6c. On the other hand, in this embodiment, the first part 6a and the second part which is the extension part are
Since a heat insulating material is placed between the portion 6b and the second portion and the third portion 6C, it is possible to prevent the occurrence of heat convection and radiation, and the temperature of each temperature control means can be controlled. This allows for accurate control.

Thus, according to this embodiment, the temperature setting of each portion 6a to 6c by the temperature control means is extremely accurate, and the length of each portion can be made shorter.

In addition, the outflow part 6 (diameter 5 mm, length 800 m
m), 3 cm of glass with viscosity log η = 3.5
3/min, but the outflow portion 6 of the second embodiment of the present invention (the diameter of the first portion 6a and the diameter of the third portion 6c are 5 mm, and the volume of the second portion 6b is about 4
), by operating the outflow control means 20, the absolute pressure inside the pipe 20a of said means is reduced to about 0.93 Kg/cm2 at appropriate time intervals and to about 1.1 Kg/cm2.
By alternating the pressure of /cm2, the viscosity is 1o.
5 to 30 with gη = 2 glass as 0.1 to 1 cm3
It could be drained intermittently at arbitrary intervals of seconds.

Although not shown in FIGS. 1 and 2 above, the molten glass g flowing out from the outlet 14 is supplied to a suitable continuous molding device, where it is continuously molded.

[Effects of the Invention] According to the present invention as described above, since the outflow portion is provided with an outflow control means for bringing the gas into contact with the molten glass and adjusting the pressure of the gas, the molten glass can be melted to a desired viscosity. This is achieved by intermittently causing the desired amount of glass to flow out at desired intervals.

Further, according to the present invention, since no mechanical means such as a plunger is provided in the molten glass, it is possible to prevent foreign matter from entering and the generation of striae, and a homogeneous molten glass is flowed out.

Furthermore, by forming an extended part with a large cross-sectional area in the middle part of the outflow part and attaching the above-mentioned outflow control means to the middle part, the heat capacity of the molten glass in the middle part is increased and the vertical amount of the extended part is increased. Thermal interference of the molten glass can be sufficiently prevented, and therefore the glass can be flowed out accurately under desired conditions.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing the structure of a molten glass outlet according to the present invention. FIG. 3 is a sectional view showing the structure of the conventional molten glass outlet. 2: Molten glass storage tank, 4.8, 10, 12, 22: Temperature control means. 6 Outlet, 6b=Expansion, 14: Outlet, 16.18: Insulation. 20: Outflow control means. Figure 1 Figure 2 Figure 3 Procedural amendment July 6, 1988 Director General of the Patent Office Kunio Ogawa 1 Indication of the case Patent application No. 128394/1982 2 Name of the invention Structure of molten glass outflow section 3 Amendment Relationship with the case of a person who does

Claims (3)

[Claims] (1) In the structure of the outflow part for flowing out molten glass from the molten glass storage tank, outflow control means for bringing gas into contact with the molten glass between the storage tank connection part and the outflow tip part and adjusting the pressure of the gas. A structure of a molten glass outflow part, characterized in that a molten glass outflow part is attached. (2) An expanded portion having a larger cross-sectional area than the leading end is provided between the storage tank connecting portion and the outflow tip, and an outflow control means is attached to the expanded portion. Structure of molten glass outflow part. (3) The structure of the molten glass outflow section according to claim 2, wherein the storage tank connection section, the tip section, and the expansion section are each independently provided with temperature control means.