JPH07138031A - Forming method of lens - Google Patents

Abstract

PURPOSE:To provide a forming method of a lens capable of forming a precise lens despite of its large diameter, by press forming a molten glass having a diameter close to the diameter of a die. CONSTITUTION:A bottom side of a lump of molten glass 2 is controlled by a bottom die 3 and at the same time the upper side of the glass is crushed with a pressure of extrusion to provide the glass to be supplied having its diameter close to the diameter of the bottom die 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for pressing a molten glass gob with upper and lower molds to obtain a lens.

[0002]

2. Description of the Related Art Conventionally, as a molding method for obtaining a lens by pressing a molten glass gob with upper and lower molds, for example, JP-A-4-14 is known.
There is an invention described in Japanese Patent No. 9032. The above invention is illustrated in FIG. 8a.
As shown in FIG. 3D, the step of dropping the molten glass gob 91 from the nozzle 90 onto the heat processing jig 92 installed below the nozzle 90 and the molten glass gob 91 by reversing the molten glass gob 91
The contact surface 91b between the heat processing jig 92 and the
This is a lens forming method including a step of reheating 1b with a heater 94 to form a glass molded body (preform) 95, and a step of pressing the glass molded body (preform) 95 with an upper and lower mold (not shown). Here, it is described that the step of reheating the contact surface 91b is for removing wrinkles which are brought into contact with the thermal processing jig 92 and are rapidly cooled, and which are generated on the contact surface 91b due to thermal contraction.

[0003]

However, in the above-mentioned prior art, the molten glass 91 is dropped on the heat processing jig 92 to form the polka-dotted molten glass 91 in the preform 95.
Therefore, the diameter of the preform 95 may become extremely smaller than the diameter of the molding die. In particular, when molding a large-diameter lens, the above can occur.

The diameter of the preform 95 is determined by the amount and viscosity of the molten glass 91 and the wettability with the heat processing jig, and these physical quantities are fixed, and the diameter is inevitably determined. On the other hand, the diameter of the molding die is a predetermined lens diameter and is also determined. For the above reason, when the diameter of the preform 95 is extremely smaller than that of the mold, it becomes difficult to spread the preform 95 over the entire surface of the mold when the preform 95 is pressed by the mold, and the shape of the mold is 95 is not precisely transferred, resulting in a problem that the shape accuracy of the molded lens is deteriorated.

Therefore, the present invention was developed in view of the above problems in the prior art, and a lens capable of supplying a molten glass having a diameter close to a desired lens diameter (that is, the diameter of the molding die) to the molding die. The purpose is to provide a molding method.

[0006]

According to the present invention, a molten glass is discharged from a nozzle and supplied to a molding surface of a lower mold, and then pressed by the lower mold and an upper mold. In this method, the molten glass is forcibly discharged from the nozzle while being received by the lower die molding surface, and the molten glass is spread and fed to the lower die molding surface.

As shown in the conceptual views of FIGS. 1 and 2, in the lens forming method of the present invention, the molten glass 2 is received by the molding surface of the lower mold 3 and is forcibly discharged from the nozzle 1, so that the molten glass 2 is lowered. This is a method in which it is spread on the molding surface of the mold 3 and supplied, and this is pressed by the upper mold 4.

In the present invention, the lower side of the molten glass 2 is the lower mold 3
The upper side is pressed by the pressure due to discharge and is crushed, and is supplied as that having a diameter close to the diameter of the lower molding die 3.

[0009]

Embodiment 1 FIGS. 3 to 5 are schematic configuration diagrams showing an apparatus used in this embodiment. Reference numeral 11 denotes a cylinder that houses the molten glass 12 therein, and the cylinder 11 is supported by an actuator 13 that is vertically movable. A hose 11a from a gas generator (not shown) is connected to the upper part of the cylinder 11. A shutter 11b that can be opened and closed is provided at the lower end of the cylinder 11. A heater 14 is installed below the cylinder 11 so as to surround the cylinder 11 when the cylinder 11 is lowered.

A lower mold 16 is installed on the base 15 below the heater 14 so as to be coaxial with the cylinder 11. A body mold 17 is fitted around the lower mold 16. A plurality of columns 18 are erected near the outer periphery of the body die 17.
The column 18 is a hole 1 formed near the outside of the pressing plate 19.
9a is loosely fitted to support the pressing plate 19 so as to be movable up and down, and the pressing plate 19 is always urged upward by the spring 20 wound around the column 18 between the pressing plate 19 and the base 15. ing.

A mortar-shaped hole 19a having an open top is provided at a position on the cylinder 11 and the body shaft at the center of the pressing plate 19. The cylinder 11, the shutter 11c, and the pressing plate 19 are made of a substance that is difficult to be fused to the molten glass, for example, carbon.

The forming method using the apparatus having the above-described structure is such that the molten glass 12 is forcibly discharged and supplied from the cylinder 11 while being received by the lower mold 16, and the upper surface of the supplied molten glass 12 has a softening temperature. It consists of a step of reheating with hot air at the above temperature and a step of press-molding the molten glass 12 placed on the lower mold 16 with the upper mold 22, and the most characteristic part is to force the molten glass 12 into force. It is a step of discharging and supplying to.

First, the shutter 11b of the cylinder 11
The glass pellet corresponding to one lens is placed inside and the cylinder 11 is lowered to the heater 14 to heat and melt the glass pellet inside. It is appropriate to set the heating temperature so that the glass has a viscosity of 10 ⁴ poise or less. Next, the cylinder 11 is lowered until it hits the pressing plate 19, and the spring 20 supporting the pressing plate 19 is contracted until the lower surface of the pressing plate 19 contacts the upper end of the barrel die 17.

Then, at the same time when the shutter 11b is opened, gas is sent from the hose 11a into the cylinder 11 to forcibly discharge the molten glass 12 therein. The discharged molten glass 12 is supplied to the lower mold 16 through the hole 19a of the pressing plate 19. However, since the upper surface of the lower mold 16 is regulated by the pressing plate 19, the molten glass 12 flows laterally and spreads, and the lower mold 16 Crim the entire surface of. That is, the molten glass having the diameter of the forming die could be supplied.

When the supply of the molten glass 12 to the lower mold 16 is completed, the cylinder 11 is immediately retracted. Then, the spring 20 extends and the pressing plate 19 is lifted and separated from the molten glass 12. Since the pressure plate 19 is not particularly temperature-controlled, it is lower than the temperature of the molten glass 12 and is made of a substance that does not easily adhere to the molten glass, so that this separation is performed quickly.

On the upper surface of the molten glass 2, the hole 1 of the pressing plate 19 is formed.
Although a separation mark due to 9a remains, it is erased by reheating the upper surface with the hot air having a temperature equal to or higher than the softening temperature by the non-frame torch 21 in the reheating step and thermally deforming it. Finally, the lower mold 16 is conveyed below the upper mold 22, and the molten glass 12 is press-molded to complete the lens molding. Here, the mold temperatures of the upper and lower molds 16 and 22 need to be adjusted in advance so as to obtain a desired lens shape accuracy. Although this temperature varies depending on the type of glass to be molded, it may be finely adjusted appropriately near the glass transition temperature.

According to this embodiment, the molten glass having a diameter close to that of the molding die can be supplied to the molding die, and the molten glass can be easily spread to every corner of the molding die during pressing. Therefore, by accurately transferring the shape of the mold to the glass, it becomes possible to mold a high-precision lens. Particularly, it is very effective when molding a large-diameter lens.

[0018]

[Embodiment 2] FIG. 6 is an enlarged sectional view of an essential part of an apparatus used in this embodiment. The present embodiment is different in that a pressing portion 19b having a concave bottom surface is formed in the lower portion of the hole 19a of the pressing plate 19 in the first embodiment, and other configurations are composed of the same constituent parts and are the same. The same numbers are given to the components and the description of the components is omitted.

Molten glass 2 was prepared in the same procedure as in Example 1.
Is supplied to the lower mold 16, the upper surface of the molten glass 12 is formed along the concave surface of the pressing portion 19b, the upper surface of the molten glass 12 is formed into a convex surface, and is supplied to the lower mold 16.

According to this embodiment, when press-molding the upper surface of the molten glass into a convex surface, the upper surface has a shape close to the final shape in advance, so that the upper surface can be easily molded. In particular, it is suitable for molding a lens having a large difference in thickness between the edge thickness and the middle thickness.

[0021]

[Embodiment 3] FIG. 7 is an enlarged sectional view of an essential part of an apparatus used in this embodiment. The present embodiment is different in that the pressing portion 19b of the pressing plate 19 in the second embodiment is formed in a convex surface, and other configurations are composed of the same constituent parts, and the same constituent parts are designated by the same reference numerals. The description of the configuration is omitted.

The molding method of this embodiment is for molding the upper surface of the molten glass 12 into a concave surface, and since the operation and effect are the same as those of the second embodiment, the description thereof is omitted.

In each of the above-mentioned embodiments, there is a wrinkle which is caused by rapid cooling of the lower surface of the molten glass by the lower mold, which is a concern in the prior art. In the method of the present invention, the molten glass is pressure-bonded to the lower mold. Therefore, the wrinkles are not stretched and caused.

[0024]

As described above, according to the lens molding method of the present invention, a molten glass having a diameter close to the diameter of the molding die is press-molded. It can be molded.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the present invention.

FIG. 2 is a conceptual diagram showing the present invention.

FIG. 3 is a schematic configuration diagram showing a first embodiment.

FIG. 4 is a schematic configuration diagram showing a first embodiment.

FIG. 5 is a schematic configuration diagram showing a first embodiment.

FIG. 6 is an enlarged cross-sectional view of a main part showing a second embodiment.

FIG. 7 is an enlarged sectional view of an essential part showing a third embodiment.

8A to 8D are explanatory views showing manufacturing processes, respectively.

[Explanation of symbols]

 1 Cylinder 2 Molten glass 3 Lower mold 4 Upper mold

Claims (1)

[Claims] 1. A molding method in which molten glass is discharged from a nozzle and supplied to a molding surface of a lower mold, and then pressed by the lower mold and an upper mold, while the molten glass is received by the molding surface of the lower mold from the nozzle. A method of molding a lens, which comprises forcibly discharging and spreading the molten glass onto a molding surface of a lower mold to supply the molten glass.