JPH0543258A - Production of globular glass - Google Patents

Abstract

PURPOSE:To inexpensively produce a globular glass with the surface specularly fire-polished, free of shear mark and uniform in weight by locally heating the lower end of a glass rod to soften and melt it, dropping the molten glass as the droplet by gravity and making the droplet globular. CONSTITUTION:A glass rod 1 having about 0.1-10mm diameter is rotated by a device 2 and supplied by a feeder 3 at a specified rate. The lower end of the rod 1 is locally heated by a carbon dioxide laser from a laser heater 4. The softened and melted glass is dropped by gravity as the droplet 11, and the droplet is made globular by the surface tension, cooled by the air introduced from an air inlet 10 to at least the distortion point in a cooling cylinder 6 and solidified. The glass 11 is recovered by a concave collecting jig 8 provided with a rotating device 9. A high-quality globular glass having a weight determined by the diameter of the glass rod 1 is obtained in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing spherical glass for preform for reheat press molding various optical lenses.

[0002]

2. Description of the Related Art As a method for producing a high-precision aspherical glass lens, a preform is once made from a glass material, placed in a pair of molding dies, heated together with a mold and press-molded. There is. The preform used at this time is required to have the following conditions.

1) At the time of pressing, the radius of curvature of the preform is smaller than that of the forming die so that a closed space is not created (the atmosphere is not confined) between the preform and the forming die. 2) To keep the lens thickness after pressing constant, the weight (volume) should be constant. 3) Since the molded lens surface requires a high degree of mirror surface, it is desirable that the surface roughness of the preform be as close to the mirror surface as possible. Also, there are no defects such as shear marks.

In order to satisfy these conditions, particularly as a preform for molding a convex lens, in order to satisfy the above condition 1), it is necessary to have a shape close to that of a finished lens or a spherical shape. Had to perform grinding and polishing in order to satisfy the above conditions 2) and 3) in order to produce preforms having these shapes.

That is, in the case of producing a preform having a shape similar to that of a finished lens, a method of making a gob from molten glass, cutting it, pressing it, annealing it, grinding and polishing it is used. Was there. Further, the spherical preform has been produced by cutting a glass block or a glass rod, and then grinding and polishing.

Further, as a method other than these, there has been proposed a method of forming a cut gob into a spherical shape in the process of rolling down the gutter-shaped passage and descending.

[0007]

However, the conventional method of polishing has a problem that it requires a lot of man-hours and a long time, which results in high cost and is not preferable for industrial use. Also,
The method of rolling a gob to form a spherical shape has a problem that it is difficult to eliminate defects such as weight controllability at the time of gob formation and cutting and shear marks.

The present invention solves the problems of the above-mentioned prior art, satisfies all the above-mentioned necessary conditions as a preform, and is inexpensive spherical preform by simple equipment and process. It provides a method for mass production.

[0009]

[Means for Solving the Problems] The lower end of the glass rod is locally heated, and only the glass in the heated portion is softened and melted to spontaneously drop as glass droplets and spherical, and is molded into a spherical shape with a constant weight. The present invention provides a method for producing spherical glass, which comprises obtaining spherical glass whose surface is a mirror surface made of fire.

In the present invention, when the lower end of the glass rod is locally heated, only the glass in the heated portion becomes in a softening and melting state and becomes spherical due to its own surface tension and hangs down.
It will eventually fall. At this moment, the following equation mg = πDγ (m: glass mass, g: gravitational acceleration, D: rod diameter,
(γ: surface tension of glass) is established. Since γ is the physical property value of glass, if the type of glass is determined, m is D
Uniquely determined by. Moreover, D can be produced accurately and inexpensively by a known method. Further, the surface roughness and the length of the glass rod are not particularly limited.

The heating device for locally heating the glass rod may be any device capable of forming a hot spot enough to melt only the end of the glass rod, and may be a gas burner, a carbon dioxide laser, an electric heater, a condensing heating device, or the like. Although it can be used, there are some glass which easily generate reboil bubbles depending on the composition of the glass. In that case, it is desirable to use a carbon dioxide gas laser, an electric heater, a condensing heating device or the like. Further, since the glass gradually drops from the rod end, it is necessary to provide a feed mechanism on the glass rod side if the heating device is fixed so that the lower end is always heated. Further, it is desirable to rotate the glass rod in order to heat it uniformly.

A collecting device for collecting spherical glass has a function of compensating for the falling glass droplets to become spherical due to the surface tension of itself and to be cooled and solidified while maintaining the mirror surface,
It is desirable that the concave tray has a mechanism capable of rotating on its own, but it is not particularly limited as long as the glass is not deformed, destroyed or contaminated by dropping. That is,
If the glass that is falling is small, it will be cooled and solidified while maintaining a nearly perfect spherical shape if the surface tension of the glass is large, so a strong impact may be applied in one direction when touching the surface of the collection jig. If there is not, the shape does not collapse, and if it is a glass of a certain size, it can be cooled and solidified while keeping the spherical shape by rolling in the collecting jig. A particularly preferred embodiment is cooling to the strain point by free fall.

There is no limitation on the kind of glass to which the present method can be applied, and the size of the spherical glass to be produced depends on the surface tension of the glass, but it is approximately 5 mg.
It is about 1 g. Therefore, the diameter range of the glass rod used is approximately 0.1 mm to 10 mm.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. A φ1.7 mm (± 0.05%) heavy flint glass rod 1 was fed vertically downward at a constant rate of 20 mm / min by a feeding device 3, and was rotated at 60 rpm by a rotating device 2. The lower end of the glass rod was heated by a carbon dioxide gas laser with a laser heating device 4 and dropped. The glass viscosity at the hot spot is about 600 poise. Drop-shaped glass 11 separated from the rod
Is cooled down to the strain point by dropping in the cooling cylinder 6 having a length of 2 m,
It is stored in the collection jig 8 and taken out. Air at room temperature introduced from the air inlet 10 is blown into the cooling cylinder to promote cooling of the glass. Also, the collection jig has a diameter of 12
Rotating device 9 is a 0 mm concave stainless steel container.
Was rotated at 60 rpm.

The 100 spherical glasses taken out had a diameter of 2.8 mm and a weight of 70 mg ± 0.8%, and had a sufficient quality as a preform for press-molding a highly accurate optical lens. Was there. In addition, the time required to create one preform was about 10 seconds.

[0016]

The spherical glass obtained according to the present invention is a mirror surface made of fire, has no defects such as shear marks, and has high weight accuracy. In addition, the equipment and process for achieving this are extremely simple, and conventional grinding,
Since polishing is unnecessary and the tact time is short, mass productivity is very high. Therefore, it is extremely effective in reducing the production cost of high quality glass lenses.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for carrying out the present invention.

[Explanation of symbols]

 1 Glass Rod 2 Rotating Device 3 Feeding Device 4 Laser Heating Device 6 Cooling Cylinder 8 Collection Jig 9 Rotating Device 10 Air Inlet 11 Glass

Claims (1)

[Claims] 1. A lower end of a glass rod is locally heated to soften and melt only the glass in a heated portion to spontaneously drop as glass droplets and to be spherical, and a surface having a constant weight and a spherical shape is made by fire. A method for producing spherical glass, which comprises obtaining a spherical glass that is a mirror surface of.