JPH0517178B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for manufacturing a glass molded product that does not cause misalignment between the center axes of the top and side surfaces of the molded product and does not involve the generation of flash. In particular, the present invention relates to a method for producing a glass molded product suitable for obtaining an optical element preform.

[Conventional technology]

Conventionally, when pressure-molding a softened glass ingot to obtain a preformed optical element, etc., an upper mold that partitions the upper surface of the molded product, a body mold that partitions the same side and has an upper mold guide, and the same are used. It is customary to use a lower mold that partitions the lower surface and slides inside the barrel mold.

In addition, during molding, as shown in FIG.
After positioning the upper mold on the upper mold guide part A of the upper mold 1,
After positioning the upper mold 1 by pressing down or supplying the softened glass lump 4 in the same manner as shown in FIG.
The product is obtained by pressing the lower die 3 and pressurizing the glass gob 4.

However, when molding glass using such a mold, the guide part A tends to wear out due to repeated use of the mold, and oxidizes due to high heat, causing dimensional changes. It becomes extremely difficult to align the shaft with the center axis of the barrel. For this reason, not only does the center axis (optical axis) of the top surface of the molded product and the center axis of the side surface become misaligned, but also there is a drawback that flash is generated at the upper end of the side surface of the molded product, which corresponds to the joint between the upper mold and the body mold. .

When the glass gob is fed into the mold, the lower part of the glass gob that comes in contact with the mold rapidly cools down and becomes highly viscous, so flash is generated at the seam between the body mold and the upper end of the lower mold. It is difficult to do this, but since the upper part of the glass gob maintains a low viscosity state, it is likely to occur at the joint between the upper mold and the body mold.

[Problems to be Solved by the Invention] The present invention has been made in order to eliminate the various drawbacks of the above-mentioned prior art. It is an object of the present invention to provide a method for manufacturing a glass molded product that does not cause molding problems and does not involve the generation of flash, particularly a method for manufacturing a glass molded product suitable for obtaining an optical element preform.

[Means for solving problems]

The present invention is based on the basic concept of manufacturing a glass molded product by regulating substantially all the side shapes of the glass molded product using the molding surface of the upper mold. A softened glass gob is fed onto a movable lower mold, and then an upper mold having a concave molding surface that defines the sides of the glass molded article substantially together with the upper surface is lowered to bring the lower edge of the upper mold above the upper mold. After setting at a predetermined position on the upper edge of the guide member, moving at least one of the upper mold and the lower mold,
The softening process involves press-fitting and molding the glass gob into a space surrounded by the concave forming surface of the upper mold, whereby the side surfaces of the glass gob are substantially regulated by the concave forming surface, followed by molding. A method for manufacturing a glass molded product, which comprises releasing a glass lump from a mold.

Therefore, the method of the present invention is characterized in that, during pressure molding of the glass gob, the upper end of the lower mold is substantially positioned at the inner joint between the lower mouth edge of the upper mold and the upper mouth edge of the guide member. Be looked at.

In addition, when releasing the above-mentioned molded glass lump,
Various mold release techniques can be added as necessary.

〔Example〕

Next, preferred embodiments of the method of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the main steps in manufacturing a preformed product for a convex lens. In FIG. 1A, the upper mold 1, the guide member 2, and the lower mold 3 that is slidable therein are all maintained at a predetermined temperature below the glass transition point.

As shown in FIG. 1A, after a softened glass lump 4 of a predetermined weight is supplied into a chamber surrounded by a guide member 2 and a lower mold 3 located at the lowest position, the upper mold 1 is lowered and the lower edge of the upper mold is guided. At the same time as the upper edge of the member 2 is brought into close contact with the upper mold guide part A, as shown in FIG. 1B, the lower mold 3 is pushed up, or as shown in FIG.
is fixed with a fixing member (not shown),
The softened glass gob 4 is press-fitted into the recessed part of the upper mold by pressing down the upper mold 1 together with the guide member 2 to give the glass gob 4 a shape. At this time, the upper end of the lower mold is positioned at the level of the lower mouth edge of the upper mold, and the side shape of the molded glass gob 4' is substantially defined and regulated by the inner circumferential wall of the concave molding surface of the upper mold 1. Then, after cooling the molded glass gob 4' to an appropriate temperature at which no deformation occurs while maintaining the glass pressurized state shown in FIG. Then, the molded glass gob 4' is removed from the lower mold 3, and it is slowly cooled to obtain a desired molded product.

If the glass gob has no surplus capacity, the upper end of the lower mold and the lower edge of the upper mold will be at the same level, but usually the glass gob has some surplus, so
Correspondingly, the upper end of the lower mold will be located slightly below this level. In any case, the main part of the side surface of the molded product is substantially defined by the upper mold 1.

In this embodiment, when the molded glass gob 4' is released from the mold, if the molded glass gob 4' comes into close contact with the concave molding surface of the upper mold 1 and is difficult to remove, as shown in FIG. A ring-shaped inlet hole leading to the external glass supply pipe 5 is provided on the concave molding surface 1', and gas is introduced between the concave molding surface and the surface of the molded glass gob in synchronization with the upward return operation of the upper mold 1. When press-fitting, the upper mold 1
The mold release operation from the mold can be easily performed. Alternatively, the inlet hole may be a plurality of independent pores, and furthermore, a suction hole communicating with an external gas suction pipe (not shown) may be provided on the upper surface of the lower mold 3 to form the glass gob 4'. The mold can be released in the same way by suctioning and holding the gas on the upper surface of the lower mold 3, or by using a combination of the above-mentioned pressurization and suction.
Note that the width of each of the holes is preferably 0.05 to 0.3 mm.

In addition, in order to obtain a molded product with a constant wall thickness, the upper mold 1
As indicated by the dotted line in FIG. 2, a gap B is appropriately provided at the lower part of the inner circumferential wall of the molding surface to allow the excess portion of the glass gob to escape.

The molded product obtained in this example has its top surface and side surfaces molded with an integrated upper mold, so there is no misalignment between the optical axis of the top surface and the center axis of the side surface, and the upper and lower ends of the side surface There is no occurrence of casting burrs. Therefore, it is excellent as a preform for lenses.

Although the embodiments have been described above, the method of the present invention is not limited to the above embodiments, and can be similarly carried out on preformed products corresponding to various known lens shapes. It can also be applied to directly manufacturing optical elements.

〔Effect of the invention〕

As described above, the method for manufacturing a glass molded product according to the present invention is a method for manufacturing a glass molded product using an upper mold having a concave molding surface that substantially defines the sides of the glass molded product together with the top surface. There is no misalignment of the central axis on the same side, and
It is possible to obtain a glass molded product with high dimensional precision without the occurrence of flash on the upper and lower ends of the side surface of the molded product.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing the main parts of the manufacturing process of an embodiment according to the method of the present invention, and FIG. 2 is an enlarged side sectional view showing an example of another upper mold used in the same embodiment. . FIG. 3 is a side sectional view for explaining the current technology. 1, 1'... Upper mold, 2... Guide member, 3... Lower mold, 4... Softened glass lump, 4'... Molded glass lump,
5... Gas supply pipe, 6... Inlet hole, 7... Trunk type,
8... Plunger earring, A... Guide section, B...
...void area.

Claims (1)

[Claims] 1. A softened glass gob is fed onto a lower mold that is slidable within a guide member, and then an upper mold having a concave molding surface that defines the side surfaces of the glass molded article substantially together with the upper surface is provided. After lowering the upper die to set the lower edge of the upper die at a predetermined position on the upper edge of the guide member, at least one of the upper die and the lower die is moved to move the softened glass lump into the concave shape of the upper die. A method for manufacturing a glass molded product, which comprises press-fitting and molding into a space surrounded by a molding surface, and then releasing the molded glass gob. 2. Claims characterized in that the molded glass gob is released from the mold using a gas inlet hole provided in the concave molding surface of the upper mold and/or a gas suction hole provided in the lower molding surface. 2. A method for producing a glass molded product according to item 1.