JPH03137026A - Method and apparatus for producing glass lens by liquid drop method - Google Patents

Abstract

PURPOSE:To allow the production of a glass drop of a large weight by providing means for blasting air to the glass drop formed at the tip of a nozzle from the direction below the glass drop. CONSTITUTION:The glass 2 is melted in a crucible 1 and is kept heated by heaters 5a to 5d so that the molten glass does not cool to a solid state and the glass drop 6 is formed at the tip of the nozzle 4. The hot air is blasted to this glass drop 6 from the direction below the glass drop 6 by a blowing up part 9 of a doughnut shape or the like which sends the hot air from a blasting hole 16 through, for example, a blasting pipe 17, by which the glass drop 6 is increased in size; thereafter, the glass drop is allowed to fall by gravity. The glass drop is captured in a mold 12 and is thereafter moved from the falling point. The glass drop is then pressed by an upper mold 13.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method and apparatus for manufacturing unpolished glass lenses.

Conventional technology The method for producing unpolished glass is the droplet method, in which molten glass is dropped from the tip of a nozzle, the falling glass droplets are received by a lower mold, and press-formed. An excellent method for obtaining lenses free of such defects has been developed by the present inventors and has already been filed (Japanese Patent Application No. 59-267058).

Although the droplet method is an excellent method for producing unpolished glass, several points that need improvement have been discovered. In order to clarify the problems that require such improvement, the droplet method will be explained in more detail with reference to FIG.

In the droplet method, first a glass (2) is melted in a crucible (1).
is made into liquid droplets of a certain size at the tip of the nozzle (4). The area from the crucible (1) to the tip of the nozzle (4) is heated by heaters (5a) to (5d) so that the molten glass does not cool down and become solid. Next, a glass droplet (6) controlled to a predetermined size and temperature is allowed to fall naturally from the tip of the nozzle (4), and is collected in an appropriate mold (12) installed at the point where the glass droplet falls. death,
After collection, move from the falling point of the glass droplet to the upper mold (13)
to obtain an unpolished glass lens.

The glass droplets formed at the nozzle tip are determined by the nozzle tip diameter, the surface tension of the molten glass, etc. In the case of conventional free fall, even for lanthanum glass, which has a high surface tension, glass droplets of maximum size of only about 4 to 5 g can be obtained. However, it was not possible to obtain anything heavier than that.

Problems to be Solved by the Invention It is an object of the present invention to solve the above-mentioned conventional problems and to provide a method and apparatus for manufacturing a glass lens using a droplet method, which can manufacture glass droplets with a weight larger than that of the conventional method. do.

Means for solving the problem, namely a glass melting crucible, provided at the bottom of the crucible,
A glass lens manufacturing apparatus equipped with a nozzle for dropping glass melted in the crucible as glass droplets from the tip thereof, further comprising an air blowing means for blowing air from the glass droplet dropping direction toward the glass droplets formed at the tip of the nozzle. The present invention relates to a glass lens manufacturing apparatus characterized by the following. Furthermore, in a droplet method glass lens manufacturing method in which a glass lens is manufactured by dropping molten glass from a nozzle tip, it relates to a glass lens manufacturing method in which a glass droplet is formed at a nozzle tip while blowing air from the glass droplet dropping direction. .

The present invention basically consists of a crucible (1) for melting glass;
, a nozzle (4) that guides the molten glass to the outside, a blow-up section (9) that blows hot air from below onto the glass droplet (6) formed at the nozzle tip, and upper and lower molds that mold the dropped glass droplet ( 12) and (13), and the structure similar to that of the conventional one can be used except for the blow-up part (9).

The weight of the glass droplet formed at the nozzle tip is generally expressed as mg=2πrγ (m: weight, g: weight acceleration, r: nozzle tip diameter, 17
surface tension). According to the present invention, by blowing air from below the glass droplet formed at the nozzle tip, the weight acceleration g of the above formula can be made smaller than the case without the blow-up part. The weight of the glass droplet can be increased. The surface tension of various optical glasses in the melting temperature range (700 to 1500°C) is 1
Since it is about 50 to 600 dyn/c+n, the maximum weight of glass droplets obtained by the conventional method was, for example, about 4 to 5 g in lanthanum-based glass, but in the present invention, it is increased to about 6 to 8 g. be able to.

The amount of air blown to the glass droplet formed at the tip of the nozzle is 1 Oml/min or more, preferably 50 ml/min or more in the case of a funnel-shaped blow-up part with an inner diameter of 10 mm as shown in FIG. 3. . Air flow rate is l Oml
/n+in, if the amount is less than that, there will be no air blowing effect and the glass droplets will not become large. Furthermore, if the amount of air blown is too large, the glass droplets will not have a spherical shape suitable for molding, and the drop positions will vary.

It is preferable that the temperature of the air be hot air matched to the temperature of the glass droplets formed at the tip of the nozzle, since this will result in glass droplets having a uniform temperature.

The configuration of the blow-up section is not particularly limited as long as it can blow hot air from below the glass droplets, but for example, as shown in FIG. Donut-shaped or third
One example is the funnel-shaped one shown in the figure.

The donut-shaped blow-up section shown in FIG. 2 is placed below the glass droplet formed at the tip of the nozzle as shown in FIG. ) air is blown towards the glass droplets.

The funnel-shaped blow-up section shown in FIG.
), hot air is sent to the funnel-shaped part, from where it is blown towards the glass droplets.

When glass droplets are dripping, they pass through the center of the blow-up part of the funnel-shaped part. allow for passage through the department.

The hot air sent to the blow-up section can be generated using a flame heater (not shown) or the like.

The crucible is equipped with a stirrer (3) to homogenize the molten glass, and the temperature of the crucible and nozzle is controlled by a heating heater (3).
5a to 5d), the desired temperature is maintained. The temperature of the crucible (1) and nozzle (4) may be set depending on the properties of the glass, the size of the glass droplets to be obtained, etc., and is usually within the range of 500 to 1400°C. In particular, if the temperature of the lower and upper parts of the nozzle (4) is set high in the lower part and low in the upper part, the glass droplets (6) can be easily dropped. Preferably the lower part is 50-200°
About C, higher than the upper part.

The temperature of the glass droplet varies depending on the falling distance, the ambient temperature, the size of the glass droplet, the temperature, the thermal conductivity of the glass, whether a forced cooling means is provided, etc., and furthermore, the temperature of the glass droplet is collected on the lower mold. Since the subsequent cooling rate of the glass droplet varies depending on the constituent material of the lower mold, the set temperature of the lower mold, etc., when implementing the present invention, the cooling rate is adjusted while taking these conditions into consideration.

Furthermore, in order to precisely control the glass temperature, it is preferable to take measures to automatically control these temperatures. As a means for this, it is preferable to control the temperature of the glass droplet at the nozzle tip by controlling the time it takes for the glass droplet to form at the nozzle tip and fall. Specifically, for example, a light beam passing through the nozzle tip is emitted by a light emitter (8), and a light receiver (9) for sensing the light is placed opposite to the light emitter with respect to the nozzle tip, and the formation of glass droplets is prevented. The time until the drop is measured, and a signal corresponding to the measured value is sent to a control unit (microcomputer, etc., not shown), which controls the nozzle tip heating means and, if necessary, a heating heater, depending on the amount of change in the time. (
5a, 5b, 5c, and 5d) may be adopted. Alternatively, the temperature of the glass droplet may be directly measured using a radiation thermometer or the like instead of the light emitter (8) and the light receiver (9).

As described above, glass droplets are formed at the tip of the nozzle under strictly temperature-controlled conditions, and while hot air is blown from the blow-up section, when the glass droplets become a predetermined size,
Stop blowing hot air from the blower and allow the glass droplets to fall.

Although not shown in FIG. 1, the falling distance may be adjusted by moving the support base of the lower mold (12) up and down. At this time, using the same control means as used for adjusting the nozzle temperature described above, the control section is activated based on the signal from the light receiver or radiation thermometer to raise and lower the support base and adjust the falling distance. Good too. Normally, glass droplets need to be allowed to fall until their surface temperature becomes lower than the softening temperature of the glass, so in the case of natural drop,
A falling distance of 0 cm or more, preferably 200 cm or more is required.

The lower mold (12) that collects the glass droplets first has a nozzle (4).
It is placed directly under the nozzle (4) to receive the glass droplets dripping from the tip of the nozzle (4), and after the glass droplets have dripped, it is moved to the molding position,
A glass lens is molded by compression molding in cooperation with the upper mold (13).

The upper mold (13) may be made of the same material as the lower mold (11), or may be made of a different material.

Moreover, the lower mold (11) for collecting may be convex or concave. The present invention is particularly effective for manufacturing convex lenses using a concave lower mold.

The lower mold (15) has a temperature of 10% higher than the softening temperature of the glass used.
-150°C1 preferably 30-100'c! It is preferable to keep it heated to a low temperature.

When using normal heavy flint type glass, approximately 4°OoC
is set to By doing so, lenses with high surface precision can be molded, and there is an effect of preventing fusion between the mold and the glass.

The upper mold (13) is heated to a temperature 111 below the softening temperature of the glass used.
It is preferable to keep the temperature heated to 10 to 150° C1<tL< 30 to 100°.

By doing so, it has the same effect as the lower mold.

According to the present invention, various types of lenses such as biconvex, biconcave, planoconvex, planoconcave, and meniscus lenses can be manufactured accurately and efficiently by selecting the upper mold and the lower mold.

Inner diameter 10mm, tip diameter 8II 1m1 length 1000mm at the bottom of the counterfeit
1.8Q of heavy flint-based glass was placed in a platinum crucible with a wlIn platinum nozzle and an internal volume of 2Q, and the glass was heated and melted at 1000° C. while stirring.

The upper part of the nozzle (400+++a+) is 800°C, the middle part of the nozzle (400mra) is 850°C, the lower part of the nozzle (200a
+m) was heated to 900℃, and the inner diameter was -10m as shown in Figure 3.
Hot air heated to 900°C is blown at a rate of 200 +nl/min using a funnel-shaped blow-up section of 5.5 g.
glass droplets were dropped.

Both the upper and lower molds use stainless steel optically polished molds for convex lenses with a diameter of 10 mm and a radius of curvature of 34.9 mm.
Place the lower mold 3m below the nozzle to catch the dripping glass,
This was transported to the upper mold position and press-molded at 400°C.

The pressed glass had an optical mirror surface and was comparable to a polished lens.

Effects of the Invention According to the present invention, a heavy glass lens can be manufactured by a droplet method.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic configuration example of an apparatus for carrying out the droplet method of the present invention. FIGS. 2 and 3 are diagrams showing an example of a schematic configuration of the blow-up section.

Claims (1)

[Scope of Claims] 1. A glass lens manufacturing apparatus comprising a glass melting crucible and a nozzle provided at the bottom of the crucible for dropping the glass melted in the crucible as glass droplets from the tip thereof, further comprising: a glass melting crucible; 1. An apparatus for manufacturing a glass lens, comprising an air blowing means for blowing air from the glass droplet toward the glass droplet formed at the tip of the nozzle. 2. In a droplet method glass lens manufacturing method in which a glass lens is manufactured by dropping molten glass from the nozzle tip, a glass lens manufacturing method involves forming glass droplets at the nozzle tip while blowing air from the glass droplet dropping direction. .