JP2509305B2 - Glass lens forming method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a glass lens molding method and apparatus in which a glass gob (glass material) is uniformly heated by an induction heating means and press-molded by a molding die.

[Conventional technology]

In recent years, instead of the glass lens processing method by grinding and polishing finishing that requires complicated steps, a method of directly press-molding with a molding die after heating and softening a pre-weighed glass gob by induction heating method by high frequency etc. (Japanese Patent Publication No. 54-38126, JP-A No. 4-4
9-81419 gazette).

FIG. 4 shows a heating state of the glass gob of this type of conventional glass lens forming apparatus. In this case, the mold 20 is a quartz tube 21.
The inner space of the quartz tube 21 is surrounded by the inert gas filled with the inert gas. An induction heating coil 22 as heating means is arranged around the quartz tube 21. The heated glass gob 23 is the lower mold of the mold 20.
24, and the glass gob 23 and the upper mold 25 are separated.

When an induction wave is oscillated by the heating coil 22 for induction heating,
Heating is concentrated on the surface portion of the molding die 20 close to the heating coil 22, that is, on the outer peripheral portions of the lower die holder 26, the upper die holder 27, the lower die holder 28 and the upper die holder 29, and from this surface portion to the inside. The heat is transferred to the lower mold 24 and the upper mold 25 by heating. The glass gob 23 is heated from below by conduction from the lower mold 24 on which the glass gob is placed and radiation from the lower mold 24 and the lower mold holder 26, and the upper mold 25 from above.
And is heated by the radiation from the upper die holder 27.

[Problems to be solved by the invention]

In this way, the glass gob 23 is heated by conduction and radiation from the lower side, and is heated only by radiation from the upper side, so the amount of heat transfer from the lower side to the upper side is different, resulting in nonuniform temperature in the glass gob 23. It will be. At that time, since the thermal conductivity of glass is extremely low, it takes time to uniformize the temperature by heat conduction in the glass, and if sufficient time is required for uniformization, the production efficiency will deteriorate. become.

The non-uniform temperature of the glass gob 23 leads to non-uniform viscosity, and when such a glass gob 23 is pressed, directional flow occurs in the glass, and excessive stretching of the glass occurs on the lower die molding surface 24a side. Insufficient glass filling occurs on the side of the upper mold forming surface 25a. As a result, as shown in FIG. 5, the edge portions of the molded glass lens 30 are not uniformly stretched on the upper side and the lower side, and burrs 31 and the like are generated, which makes it difficult to obtain a satisfactory lens shape. In addition, there is a problem that uneven shrinkage and sink marks occur due to uneven temperature on the lens surface after molding.

The present invention has been made in view of the above problems, and an object thereof is to provide a glass lens molding method and apparatus capable of achieving uniform temperature distribution of a glass gob before press molding.

[Means for solving problems]

In order to achieve this object, the method of molding a glass gob lens according to the present invention, the glass gob is heated by induction heating means from the periphery of the mold with the glass gob in contact with the upper mold surface and the lower mold surface. The glass gob is press-molded at the temperature of.

Further, the glass lens molding apparatus according to the present invention presses the molding die with a molding die having an upper die and a lower die, an induction heating means provided around the molding die, and a large pressure required for press molding. Means, and means for pressurizing the molding die with a small pressure to bring the glass gob into contact with the upper mold molding surface and the lower mold molding surface when the glass gob is heated.

[Action]

In the present invention, since the glass gob is heated in a state where the glass gob is in contact with the upper mold surface and the lower mold surface, heat is similarly transferred to the glass gob from the upper side and the lower side by conduction and radiation, and the glass gob is uniformly distributed. Be heated.

〔Example〕

Next, a glass lens molding method and apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view of the entire glass lens molding apparatus according to this embodiment. In FIG. 1, reference numeral 1 is a frame of the molding apparatus, and 2 is a molding chamber which is isolated from the external atmosphere by a quartz tube 3. The molding chamber 2 is filled with an inert gas to prevent the mold 4 from being oxidized. An induction heating heating coil 5 as an induction heating means is arranged around the quartz tube 3. The upper die of the molding die 4 is attached to the tip of the upper fixed shaft 7 via the heat insulating material 6a, and the lower die is attached to the tip of the movable lower shaft 8 via the heat insulating material 6b. Pressurizing means 11 and 12 act on the lower end of the lower shaft 8. The pressing means 11 is for applying a large pressure necessary for press molding to the lower mold of the molding die 4, and the pressing means 12 causes the glass gob to lightly contact the molding surface of the upper mold when the glass gob is heated, as described later. In order to apply a small pressure required for the lower mold, both pressurizing means 11 and 12 are formed as a piston / cylinder device. The cylinder of the pressurizing means 12 is attached to the tip of the piston rod 11a of the pressurizing means 11, and the tip of the piston rod 12a of the pressurizing means 12 acts on the lower end of the lower shaft 8.

In this way, since the pressurizing means unique to press molding and the glass gob contact are provided, the press molding pressure and the glass gob contact pressure can be accurately controlled. But,
It is also possible to use one pressurizing means and change the pressure of the pressure medium supplied to the cylinder of the pressurizing means depending on the pressurizing state.

FIG. 2 shows a heated state of the glass gob of the glass lens forming apparatus according to the present invention shown in FIG. In this state, the lower mold 14 on which the glass gob (glass material) 13 is placed is lifted by the pressing means 12, and the glass gob 13 is in light contact with the molding surface 15a of the upper mold 15. This contact pressure is set so that the glass gob 13, the upper mold molding surface 15a, and the lower mold molding surface 14a are not scratched, and the expansion of the glass gob 13 and the molding die 4 that occurs during heating can be absorbed. Therefore, the pressurizing means 12 is preferably formed as a pneumatic piston-cylinder device.

The molding die 4 includes this die 1 in addition to the lower die 14 and the upper die 15 described above.
Lower mold holder 16 and upper mold holder 17 surrounding 4, 15 in an annular shape
And a lower die support 18 and an upper die support 19.

Next, a method of molding a glass lens by the glass lens molding apparatus having the above structure will be described.

First, the glass gob 13 weighed in advance is placed on the lower mold 14, and the pressure medium is supplied to the pressurizing means 11 to reach the intermediate stop position.
To rise. Then, a pressure medium is supplied to the pressurizing means 12 to raise the lower mold 14, and as shown in FIG.
Is lightly contacted with the upper mold surface 15a and held. In this state, an induction wave such as a high frequency is oscillated by the induction heating heating coil 5 to heat the internal molding die 4 and the glass gob 13.

The heating by the heating coil 5 for induction heating is performed by the surface portion of the molding die 4 close to the heating coil 5, that is, the lower die holder 1.
6. The upper die holder 17, the lower die holder 18, and the upper die holder 19 are concentrated on the outer peripheral portions of the upper die holder 19, and the heat is transferred from the surface portion to the inside by conduction, so that the lower die 14 and the upper die 15 are heated. And the glass gob 13 is heated from the lower side by conduction from the lower mold 14 on which the glass gob is placed, and the radiation from the lower mold 14 and the lower mold holder 16, and from the upper side by conduction from the upper mold 15. , Is heated by radiation from the upper mold 15 and the upper mold holder 17. Therefore, the glass gob 13 is heated uniformly from the upper side and the lower side, so that the temperature distribution and hence the viscosity become uniform.

Next, the pressure medium is supplied again to the pressurizing means 11 to raise the lower die 14, and the glass gob 13 is press-formed with the upper die 15.

The glass lens 13a thus obtained has no variation in the fluidity of the glass gob 13 during press molding,
As shown in FIG. 3, the edge portion of the glass lens extends uniformly, and burrs (see FIG. 5) do not occur.

As described above, by uniformly heating the glass gob 13, it becomes possible to mold a new-type glass lens having a large viscosity change with temperature change, which is difficult to mold due to many problems in the conventional method.

Further, conventionally, during induction heating, a guided wave acts on a specific glass component (for example, an alkali component) and the glass gob oscillates on the lower mold, so that a glass gob containing the specific glass component cannot be molded. However, in the molding method according to the present invention,
Since the glass gob is held in contact with the upper mold and the lower mold, the rocking can be prevented, and the glass lens containing the specific component can be molded.

〔The invention's effect〕

As is clear from the above description, in the glass lens molding method and apparatus according to the present invention, the glass gob is heated while the glass gob is in contact with the upper mold surface and the lower mold surface. Heat is transferred from the same by conduction and radiation, and the glass gob is heated uniformly. Therefore, there is an excellent effect that the fluidity of the glass at the time of the subsequent press molding becomes uniform, and a glass lens having an accurate shape and high quality can be molded.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the entire glass lens forming apparatus according to an embodiment of the present invention, and FIG. 2 shows a positional relationship between a forming die and glass at the time of heating a glass gob in the glass lens forming apparatus of FIG. FIG. 3 is a vertical sectional view showing the shape of a glass lens molded by the glass lens molding apparatus shown in FIGS. 1 and 2, and FIG. 4 is a glass gob in a conventional glass lens molding apparatus. FIG. 5 is a vertical sectional view showing the positional relationship between the molding die and the glass gob during heating, and FIG.
It is a longitudinal cross-sectional view which shows the shape of the lens shape | molded by the conventional glass lens shaping | molding apparatus of the figure. 1 ... Frame, 2 ... Molding chamber, 3 ... Quartz tube, 4 ... Mold, 5 ... Induction heating means (heating coil for induction heating), 6
a, 6b ... Insulation material, 7 ... Upper fixed shaft, 8 ... Lower shaft, 1
1,12 …… Heating means, 11a, 12a …… Piston rod, 13…
… Glass gob, 13a …… Glass lens, 14 …… Lower mold, 14a
...... Lower mold surface, 15 …… Upper mold, 15a …… Upper mold surface, 16
...... Lower mold holder, 17 …… Upper mold holder, 18 …… Lower mold support, 19 …… Upper mold support

Claims (2)

(57) [Claims] 1. A glass characterized in that the glass gob is heated by induction heating means from the periphery of the mold with the glass gob in contact with the upper mold surface and the lower mold surface, and the glass gob is press-molded at a desired temperature. Lens molding method. 2. A molding die having an upper die and a lower die, an induction heating means provided around the molding die, a means for pressurizing the molding die with a large pressure necessary for press molding, and an upper portion for heating the glass gob. An apparatus for molding a glass lens, comprising: a means for pressing the molding die with a small pressure to bring the glass gob into contact with the molding surface and the lower molding surface.