JP2664658B2 - Glass forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass forming technique and, more particularly, to a method for forming a glass by receiving molten glass flowing down from an outflow nozzle. Such a forming method of glass is suitably used for press forming of a glass material for manufacturing an optical element such as a lens, or press forming of an optical element itself.

[0002]

2. Description of the Related Art Conventionally, an optical element such as a lens is generally manufactured through mechanical grinding and polishing steps. As a blank for manufacturing such an optical element, a blank formed by press-forming molten glass to a size slightly larger than a finished size is used.

Further, recently, an optical element has been manufactured by press molding without going through the above-mentioned mechanical grinding and polishing steps. For such press forming, a reheat press method in which a glass material having a size close to the finished dimensions is prepared in advance and the material is heated and softened to perform press forming, or a molten glass is directly housed in a mold of a forming apparatus and press formed. And a direct press method. As a glass material for the reheat press method, a material obtained by press-forming molten glass (preform) may be used.

In the press molding of optical glass as described above,
The molten glass is connected to the lower part of the melting tank and flows down from an outflow nozzle that opens downward, and is supplied to the forming apparatus. However, it is preferable that the forming apparatus performs the forming operation at regular time intervals. It is required that the outflow amount of glass per unit time is always kept constant, and the outflow molten glass is cut by a shear at a certain timing to supply a certain amount of molten glass to a forming apparatus. The outflow from the nozzle is controlled by the heating temperature of a heater attached to the nozzle.

[0005] However, glass melting is generally performed in a batch system in which a predetermined amount of glass material is accommodated in a glass melting tank and then heated and melted. As the glass flows out, the amount of molten glass in the melting tank gradually decreases. Come. Therefore, if the temperature of the molten glass in the outflow nozzle was kept constant,
As the outflow pressure gradually decreases, the outflow decreases gradually. Therefore, in order to keep the outflow amount constant, the glass viscosity is reduced by gradually increasing the temperature of the molten glass in the outflow nozzle portion.

However, according to the above method,
Although it is possible to keep the outflow or supply of molten glass constant, the viscosity of the outflow glass changes. If the viscosity is too high, molding may be difficult. On the other hand, if the viscosity is too low, there is a problem that fusion may occur to a mold member.

Therefore, the present invention solves the above-mentioned problems in the conventional molten glass supply, and realizes a molten glass supply capable of simultaneously achieving a desired supply amount and a desired viscosity of the molten glass. It is intended to perform good glass forming processing.

[0008]

According to the present invention, as a means for achieving the above object, a glass material is melted in a melting tank and discharged from an outlet, and the discharged molten glass is formed by an optical element forming means. In the forming method, the amount of the glass in the melting tank is detected, and the amount of the molten glass flowing out from the outlet is controlled based on the detection result, and the supply amount of the molten glass to the forming means is adjusted. And a method of forming and processing glass.

Further, a means for heating the molten glass, a means for cooling the molten glass, and a means for measuring the temperature of the molten glass are arranged in a flow path of the molten glass flowing down from the outflow nozzle. An apparatus for supplying molten glass, comprising: a control unit for operating the heating unit and the cooling unit based on the temperature of the molten glass measured by the measuring unit.

Further, in the method in which molten glass flows out and is supplied from an outflow nozzle connected to a glass melting tank, the outflow amount from the outflow nozzle is adjusted by controlling the temperature of the molten glass in the outflow nozzle. A method for supplying molten glass, characterized in that the viscosity of the molten glass is adjusted by controlling the non-contact temperature of the molten glass flowing out of the molten glass. Here, the non-contact temperature control for the molten glass can be performed based on the measured outflow molten glass temperature and the set value of the outflow glass temperature.

[0011]

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

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a molten glass outflow apparatus used in carrying out a glass forming method according to a reference example of the present invention.

In the figure, reference numeral 2 denotes a glass melting tank;
Is a heater for melting and keeping heat provided in the melting tank. A nozzle 6 for outflow of molten glass is provided at the bottom of the melting tank 2.
Is attached. Reference numeral 8 denotes an outflow amount adjusting heater attached to the outflow nozzle 6. Reference numeral 10 denotes a molten glass housed in the melting tank 2 and discharged from the outflow nozzle 6. The temperature of the heater 8 is controlled by a control system (not shown) so that a predetermined flow rate can be obtained regardless of the amount of residual molten glass in the melting tank 2.

Below the outflow nozzle 6, a shear 12 for cutting the outflow molten glass is arranged. Below the shear portion, a non-contact temperature sensor 14 for measuring the temperature of the molten glass 10 flowing down. Is arranged. Further, a heater 16 for heating the outflow molten glass 10 and a cooler 18 for cooling the outflow glass are provided below the sensor.
Is arranged. Both these heaters and coolers change the temperature of the molten glass without contact,
For example, a condenser infrared lamp or a laser can be used as the heater 16, and a blower can be used as the cooler 18.

Reference numerals 20, 22, and 24 denote the lower mold member, the trunk mold member, and the lower mold member and the trunk mold member, respectively, arranged below the outflow nozzle 6 in the direction of arrow A (I).
→ (II) → (III) Reference numeral 26 denotes an upper mold member which is disposed above the lower mold member 20 and the body mold member 22 at the movement position (II) and is movable vertically. Reference numeral 28 denotes molten glass supplied from the nozzle 6 onto the lower mold member 20 at the position (I);
Is molded glass.

Reference numeral 32 denotes a reference temperature setting device for setting a desired temperature of the molten glass supplied to the press forming apparatus. This corresponds to setting the desired viscosity of the supplied molten glass. The reference temperature θ ′ output from the setter 32 and the actual temperature measurement value θ of the outflow molten glass 10 output from the temperature sensor 14 are input to a subtractor 34, which outputs Δθ = (Θ′−θ) is output.

The signal Δθ is input to the controller 36. The controller performs the following operation according to whether the above Δθ is positive or negative. (1) When Δθ> 0 W = Kph ｛Δθ + (∫Δθdt) / Tih + Tdh (dΔθ
Here, Kph, Tih, and Tdh are a proportional gain, an integral time, and a derivative time for controlling the heater 16, respectively. (2) When Δθ <0 Q = −Kpn ｛Δθ + (∫Δθdt) / Tin + Tdn (dΔ
θ / dt)｝ Here, Kpn, Tin, and Tdn are a proportional gain, an integration time, and a differentiation time for controlling the cooler 18, respectively.

When Δθ> 0, the controller 36 outputs the W. This signal is D /
The heat is input to the thyristor 40 via the A-converter 38, whereby the calorific value of the heater 16 is set, and the heater operates to heat the molten glass 10 flowing down from the nozzle 6.

If Δθ <0, the controller 3
6 outputs the above Q. This signal is input to the flow control valve 44 for the blower 18 via the D / A converter 42, the valve opening is set in accordance with the signal, and the blower 18
From the nozzle 6 to cool the molten glass 10 flowing down from the nozzle 6.

When Δθ is 0, there is no output from the controller 36, and neither the heater 16 nor the cooler 18 operate.

FIG. 2 is a schematic diagram showing the operating state of the heater 16. In this case, since Δθ> 0, the diameter d ₁ of the molten glass 10 flowing out of the nozzle 6 is larger than a desired diameter. The temperature of the molten glass is increased by heating at the heater position, the viscosity is reduced, the fluidity is increased, the diameter is reduced, and the molten glass has a value d close to the desired diameter.

FIG. 3 is a schematic view showing an operation state of the cooler 18. In this case, since Δθ <0, the diameter d ₂ of the molten glass flowing out of the nozzle is smaller than the desired diameter and the viscosity is low. The temperature of the molten glass is lowered by cooling at the cooler position, and the fluidity is reduced.
The viscosity is such that it does not fuse to the mold member even when supplied to the top.

As described above, in the above embodiment, a desired viscosity is obtained by performing so-called PID control on the temperature of the outflow molten glass.

Therefore, even if the cutting operation timing of the shear 12 is kept constant, the weight and viscosity of the molten glass supplied to the forming apparatus can be made predetermined.
There is a great advantage that it is not necessary to change the press timing of the molding apparatus.

In FIG. 1, the molten glass which has flowed out of the nozzle 6 and cut by the shear 12 is accommodated on the lower mold member 20 at the position (I), moved to the right by the conveyor 24, and then moved to the position (I). In (II), the upper die member 26 moves downward to perform pressing, and is moved rightward by the conveyor 24 to reach the position (III).

FIG. 4 is a view showing a schematic configuration of an embodiment of a molten glass outflow device used in carrying out the glass forming method according to the present invention. In this figure, the same members as those in FIG. 1 are denoted by the same reference numerals.

In this embodiment, the temperature measuring sensor 14 is arranged above the shear 12 and the heater 16 and the cooler 18 are arranged to heat and cool the outflowing molten glass 10 immediately below the nozzle 6. .

In this embodiment, the control of the heater 16 and the cooler 18 is different from the embodiment of FIG. That is, in the present embodiment, it is possible to control the outflow amount of the molten glass 10 flowing out of the nozzle 6 described in the embodiment of FIG. The measured temperature signal from the temperature sensor 14 is input to the controller 50. The level of the residual molten glass in the melting tank 2 is detected by the liquid level gauge 52, and the output signal is input to the controller 52. The controller stores in advance the relationship between the residual amount and the temperature in the nozzle 6 at which a desired outflow amount is obtained, and the controller 50 sets the temperature at which the desired outflow amount is obtained based on the relationship. signal W ₁ is input to the thyristor 56 through the D / a converter 54, thereby heating value of the heater 8 is set. However, in practice, a desired amount of outflow may not be obtained due to various conditions. For this reason, the controller 50 determines how much the actually detected outflow molten glass temperature deviates from the desired temperature. desired namely actual runoff calculates how much corresponds to or deviation are) from the desired outflow, at the same time correcting the signal W ₁ in accordance with the shift amount, the actual outflow molten glass temperature The following signal is output depending on whether the temperature is higher or lower than the outflow glass temperature. (1) signal W ₂ of a magnitude proportional to the amount of deviation is input to the thyristor 40 through the D / A converter 38 in this case when the actual outflow molten glass temperature is lower than the desired outflow glass temperature, which Thus, the heat value of the heater 16 is set, the heater is operated, and the outflow molten glass 10 is heated. (2) When the actual outflow molten glass temperature is higher than the desired outflow glass temperature In this case, a signal Q ₁ having a magnitude proportional to the above-mentioned deviation amount is passed through the D / A converter 42 to the flow rate for the blower 18. Air is input to the control valve 44, the valve opening is set in accordance with the signal, air is discharged from the blower 18, and the molten glass 10 is cooled.

According to the present embodiment, in adjusting the temperature of the molten glass flowing out, a quick response that cannot be obtained only by controlling the temperature of the heater 8 of the nozzle 6 can be obtained, and more accurate control of the flow rate can be achieved. Become.

[0030]

According to the present invention as described above, good glass forming can be performed by adjusting the amount of glass supplied to the forming means. In particular, a means for heating the molten glass, a means for cooling the molten glass, and a means for measuring the temperature of the molten glass are arranged in a flow path of the molten glass flowing down from the outflow nozzle, and the temperature is measured by the temperature measuring means. By operating the heating means and the cooling means based on the temperature of the molten glass, the flow rate of the molten glass flowing out of the outflow nozzle is adjusted by controlling the temperature of the molten glass in the outflow nozzle. By adjusting the viscosity of the molten glass by non-contact temperature control of the glass,
Molten glass having a desired viscosity can be supplied in a desired supply amount.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a molten glass outflow device used in carrying out a reference example of the method of the present invention.

FIG. 2 is a schematic diagram showing an operation state of a heater.

FIG. 3 is a schematic view showing an operation state of a cooler.

FIG. 4 is a diagram showing a schematic configuration of a molten glass outflow device used in carrying out the method of the present invention.

[Explanation of symbols]

 2 Glass melting tank 4, 8 Heater 6 Outflow nozzle 10 Molten glass 12 Shear 14 Temperature sensor 16 Heater 18 Cooler 20 Lower mold member 22 Body mold member 24 Conveyor 26 Upper mold member 28 Molten glass 30 Molded product

Claims (1)

(57) [Claims] 1. A method of melting a glass material in a melting tank and flowing out from an outlet, and forming the outflowing molten glass by an optical element forming means, wherein an amount of the glass in the melting tank is detected, Controlling the amount of molten glass flowing out from the outlet based on the detection result,
A method of forming and processing glass, comprising adjusting a supply amount of molten glass to the forming means.