JPH05221657A - Cutting method for glass rod - Google Patents

Abstract

PURPOSE:To provide high-quality molten glass gob. CONSTITUTION:A glass rod 1 is made to descend and stopped at a specified position determined according to a desired size of molten glass gob (process a). Next, a cutting member 2 is driven and the glass rod 1 is firmly held under a specified load (process b). In this state, hot air is sprayed from a heating nozzle 6 onto the tip of the glass rod 1 to soften the tip (processes c and d). Thereby, the viscosity of the tip is reduced, and at a point when the load applied on the cutting member 2 reached a specified level determined by a load detector 3, the cutting member 2 is driven to cut the tip of the glass rod 1, thus obtaining a desired molten glass gob (process e).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting and cutting rod-shaped glass such as optical glass.

[0002]

2. Description of the Related Art Recently, a method for producing a glass molded part having high shape accuracy and surface quality by simply heating and pressing a glass material without the need for grinding or polishing has been established. As such a manufacturing method, a manufacturing method applying a direct press method which has already been put into practical use is considered. According to such a direct press method, the molten glass heated and melted in the crucible is caused to flow down from the orifice, cut at a predetermined timing by a cutting member such as a shear device, and a predetermined amount of molten glass lump is supplied to the mold. Since the press molding is performed after that, the processing steps are significantly shortened as compared with the grinding / polishing method, and the processing cost of the optical component can be significantly reduced.

However, in the direct press system,
Glass melting is performed by putting a glass material in a crucible and heating and melting it all at once, which is not suitable for small lot production of 100 kg or less per lot. When the type of glass to be melted is changed, crucible replacement and cleaning work are required each time, which causes an increase in setup time and a significant decrease in production efficiency. Further, since the molten glass is stored in the crucible, volatilization of glass components and mixing of impurities are likely to occur during the storage, resulting in deterioration of quality of the molded optical element.

As a means for solving the above-mentioned drawbacks of the conventional direct press system, for example, Japanese Patent Application Laid-Open No. 62-29263.
The methods described in Japanese Patent Publication No. 1 and Japanese Patent Laid-Open No. 63-210036 are known. The former Japanese Patent Application Laid-Open No. 62-292631 discloses a technique in which a glass round bar is heated and continuously pressed by a pair of dies opposed to each other. In the latter Japanese Patent Laid-Open No. 63-210036, a glass round bar is heated by a first heater, is temporarily stored in a funnel-shaped container, and is further discharged at a predetermined viscosity, temperature and flow rate. The technique of heating and melting with the heater of is disclosed.

[0005]

By the way, the above-mentioned prior art has the following problems. That is, JP-A-62-2
In the technique described in Japanese Patent No. 92631, a glass round bar that has been softened by heating is directly pressed, so that a glass surplus portion with respect to the final molded optical element becomes large, which is extremely uneconomical. Also, it is necessary to remove the excess part by post processing,
There is a problem that leads to an increase in processing cost.

Further, the technique disclosed in Japanese Patent Laid-Open No. 63-210036 has the effect that the amount of glass melted at one time can be reduced as compared with the conventional direct press system, but the glass is finally obtained. It is the same as the conventional direct press system in that molten glass is supplied by flow, and heating is required until the viscosity becomes 10 to 10 ³ poise. Therefore, problems such as "volatilization of molten glass", "bubble entrainment", "fluctuation in flow rate", etc., which tend to occur as the glass viscosity decreases, cannot be solved. Furthermore, a funnel-shaped container corresponding to the crucible in the conventional direct press system is required, and when the type of glass to be melted is changed, the setup work of replacing the funnel is required as in the conventional case. There's a problem.

In order to solve the above-mentioned problems, the present inventors fixed a glass round bar to a chuck part, lowered it, and only the tip part was heated and softened by a local heating means, and at the same time, an upper part. An experiment was repeated and tried on a glass melting method and apparatus in which a temperature adjusting means was provided in the surroundings so that the portions other than the tip were not softened.

According to this method and apparatus, when the glass is melted, it is not necessary to carry out a storage member for the molten glass such as a crucible and a setup operation such as exchange and cleaning of the storage member, and especially when melting a glass of a small lot. There is an advantage that production efficiency can be improved. Further, it is possible to obtain a good quality molten glass gob without problems such as volatilization at the time of melting the glass and inclusion of bubbles. Further, there is an advantage that it is possible to prevent the phenomenon that the whole glass rod is deformed by its own weight due to excessive heating except for the tip portion, which is a problem when the glass rod material is heated and melted.

It has been found, however, that the above-mentioned method can solve various conventional problems, but has new problems. That is, the target area for heating and melting of the glass round bar tip is determined according to the size of the required molten glass gob, but since it is melting by local heating, the target area becomes a predetermined viscosity state at the timing. It is necessary to cut the tip of the glass round bar. However, if the cutting timing is too early and the glass rod is not softened sufficiently, the flowability of the cut gob will be insufficient and good transferability will be obtained even if it is attempted to press-mold it. I can't. In an extreme case, there is a problem that the glass round bar is too hard and damages the cutting member. On the other hand, if the cutting timing is too late, the time for heating and melting the tip of the round glass rod becomes excessively long, and there is a problem that quality deterioration such as volatilization of glass components and mixing of impurities is likely to occur.
As described above, it has been found that problems occur due to early or late cutting timing, which causes a decrease in productivity and quality.

The present invention has been made in view of the above problems, and when locally heating the tip portion of a glass rod, when the required tip region of the glass rod reaches a predetermined viscosity state, this is done. An object of the present invention is to provide a method for cutting a rod-shaped glass, which can be cut to obtain a molten glass gob of good quality.

[0011]

In order to achieve the above object, the present invention, when cutting a rod-shaped glass, first press a cutting member against a predetermined portion of the glass rod with a predetermined load,
Next, while the desired portion of the tip of the glass rod is being heated by the local heating means, the viscosity state of the tip of the glass rod is detected through the cutting member, and when the viscosity state of the tip of the glass rod reaches a predetermined level, the cutting member Was driven to cut the tip of the glass rod. It should be noted that the detection of the viscosity state may be performed by any one of means for changing the pressing force with which the cutting member presses the glass rod, the amount of displacement of the cutting member due to softening of the glass rod, or a combination of both.

[0012]

According to the present invention, the cutting member is pressed against a predetermined portion of the glass rod with a predetermined load, and then the desired state of the tip of the glass rod is heated by the local heating means while the viscosity state of the tip of the glass rod is maintained. Is detected via the cutting member, and when the viscosity state of the glass rod tip reaches a predetermined level, the cutting member is driven to cut the tip of the glass rod, so the cutting timing can be made accurate and high. It is possible to easily obtain a quality molten glass gob and to remarkably improve the productivity.

[0013]

[Embodiment 1] FIG. 1 is a process diagram showing a melting and cutting process of this embodiment, and FIG. 2 is a graph showing the process cycle of FIG. 1 in which the vertical axis represents load and the horizontal axis represents time. In the figure, 1 is a glass rod, which is held so as to be movable up and down by a holding means (not shown). Reference numeral 2 denotes a cutting member (for example, a shearing device) including a pair of blades that move relative to each other (horizontal direction in the drawing), and is arranged on the lower tip side of the glass rod 1 in the drawing. A driving source 5 for operating a pair of blades is connected to the cutting member 2, and a load detector 3 and a controller 4 are connected between the driving source 5 and the cutting member 2. A heating nozzle 6 is provided on the tip side (lower side in the figure) of the glass rod 1, and a desired melting and cutting apparatus is provided by heating and melting the tip portion of the glass rod 1 by hot air 7 jetted from the heating nozzle 6. Are configured.

Next, a method of cutting a glass rod in the above-mentioned melt cutting device will be described. First, as shown in FIG. 1A, the glass rod 1 descends and stops at a predetermined position determined by the desired size of the molten glass gob (see FIG. 2A). Next, as shown in FIG. 1 (step b), the cutting member 2 is driven and a predetermined load (W1) is applied.
The glass rod 1 is clamped by (see FIG. 2B). In this state, as shown in FIGS. 1C and 1D, hot air 7 is jetted from the heating nozzle 6 toward the tip 8 of the glass rod 1 to soften the tip 8 of the glass rod 1. Begins. As shown in FIG. 2C, the load acting on the cutting member 2 gradually decreases from the initial value (W1) as the tip 8 of the glass rod 1 softens (that is, the viscosity decreases).

The load (W2) in FIG. 2 indicates the load acting on the cutting member 2 when the tip portion 8 of the glass rod 1 is softened to reach a predetermined viscosity state and is set in advance. It is the value.

The viscosity of the tip portion 8 of the glass rod 1 decreases,
When the load detector 3 detects that the load acting on the cutting member 2 reaches a predetermined load (W2) (see (d) part of FIG. 2), this detection signal is input to the controller 4 and the controller 4 The operation of the driving source 5 is started by the output signal of 4 to drive the cutting member 2, and the tip portion 8 of the glass rod 1 is cut as shown in FIG. 1 (step e) to obtain a desired molten glass gob 9. (See (e) of FIG. 2).

[0017]

[Embodiment 2] FIG. 3 is a process diagram showing a melting and cutting process of this embodiment, and FIG. 4 is a graph showing the process cycle of FIG. 3 in which the vertical axis represents displacement and viscosity and the horizontal axis represents time. Is.
In addition, Example 2 is the load detector 3 in Example 1 described above.
However, the other common members are denoted by the same reference numerals as in the first embodiment, and detailed description thereof will be omitted.

That is, in the melting and cutting apparatus according to the second embodiment, first, as shown in FIG. 3 (step a), the glass rod 1 descends and stops at a predetermined position determined by the desired size of the molten glass gob. (Refer to (a) part of FIG. 4). Next, as shown in FIG. 3B, the cutting member 2 is driven to hold the glass rod 1 with a predetermined load (W) (see (b) part in FIG. 4). In this state, as shown in FIGS. 3C and 3D, hot air 7 is jetted from the heating nozzle 6 toward the tip of the glass rod 1 to soften the tip 8 of the glass rod 1. Begins. As the viscosity of the tip portion 8 of the glass rod 1 decreases, the cutting member 2 gradually moves under the initial load (W) as shown in the displacement curves of FIGS. 4 (c) and 4 (d). It progresses inward.

The displacement amount (x) of the cutting member 2 in FIG.
Is a value preset in accordance with the predetermined viscosity of the tip portion 8 of the glass rod 1.

The viscosity of the tip portion 8 of the glass rod 1 decreases,
When the displacement gauge 10 detects that the displacement amount of the cutting member 2 has reached a predetermined value (x), this detection signal is input to the controller 4, and the output signal of the controller 4 operates the drive source 5. When started, the cutting member 2 is driven, and the tip portion 8 of the glass rod 1 is cut as shown in FIG. 3 (step e) to obtain a desired molten glass gob 9 (see FIG. 4 (e)).

In the second embodiment, the amount of displacement of the cutting member 2 due to the softening of the glass rod 1 is used as a parameter.
The load (W) applied to the glass rod 1 needs to be larger than that in the first embodiment. However, since the softening state is detected while performing the cutting operation, there is an advantage in improving productivity.

[0022]

As described above, according to the method for cutting a glass rod according to the present invention, when melting and cutting the glass rod, the cutting member is pressed against the glass rod in advance, and the glass rod is inserted through the cutting member. The viscosity state of the tip of the is detected (change of pressing force or displacement of cutting member, combination of both) and cutting is performed when a predetermined viscosity state is reached, so cutting may be performed in an insufficiently softened state, or It is possible to always obtain a molten glass gob with stable quality without excessive softening.
Further, troubles such as breakage of the cutting member can be prevented. Further, unnecessary heating is not performed, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a process diagram showing a melt cutting process according to a first embodiment of the present invention.

FIG. 2 is a graph of a process cycle according to a relationship between load and time in the first embodiment.

FIG. 3 is a process diagram showing a melt cutting process according to a second embodiment of the present invention.

FIG. 4 is a graph of a process cycle according to a relationship between displacement amount and viscosity and time in the same Example 2.

[Explanation of symbols]

 1 glass rod 2 cutting device 3 load detector 4 controller 5 drive source 10 displacement detector

Claims (2)

[Claims] 1. A method of cutting a rod-shaped glass, which comprises melting and cutting the tip of a glass rod by heating, wherein a cutting member is pressed against a predetermined portion of the glass rod with a predetermined load, and the viscosity of the tip of the glass rod heated in this state. The state is detected via the cutting member,
A method for cutting a rod-shaped glass, characterized in that the cutting member is driven according to the detection signal to cut the tip of the glass rod. 2. The detection of the viscosity state is based on at least one of a change in pressing force of the cutting member pressing the glass rod or a displacement amount of the cutting member due to a decrease in the viscosity of the glass rod. The method for cutting a rod-shaped glass according to claim 1, wherein: