JPH0781954A - Forming method and forming device for optical element - Google Patents

Abstract

PURPOSE:To assure the flow property of an excess glass projecting to the outer periphery of a punch at the time of press forming. CONSTITUTION:The outer periphery of the punch 1 is freely slidably provided with an auxiliary mold 4. The spacing between the punch 1 and a drum mold 3 is sealed by this auxiliary mold 4 at the time of starting press forming of a plane preform to form a space in which the excess glass 8 of the plane preform extruding to the outer periphery of the punch 1 flows. The space corresponding to the extruding amt. of the excess glass 8 increasing with press forming is continuously formed while a round chamfer 4a formed at the front end of the bore of the auxiliary mold 4 and the excess glass 8 are brought into contact with each other by rising the auxiliary mold 4 by means of an projecting ring 6 in correspondence to rising of a die 2 at the time of press forming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for molding an optical element in which a glass gob is heated and softened and then pressure-molded by a pair of upper and lower molds.

[0002]

2. Description of the Related Art Conventionally, when forming an aspherical surface in the molding of a glass press lens, it is general to use a preform polished to a spherical surface close to a desired lens surface as a molding material. But in this case
The manufacturing cost is high because of the double processing cost of polishing and pressing the preform.

Therefore, in order to reduce the manufacturing cost,
Recently, a molding method using a flat preform as a preform has been widely used. When a flat preform is used, the amount of deformation is naturally large and the amount of extra wall protruding to the outer periphery is large as compared with a polished spherical preform. If the excess thickness does not flow smoothly, it becomes difficult to process a predetermined shape when the outer peripheral thickness is thin and the flow amount is particularly large, such as in a convex lens having a large degree of uneven thickness.

Therefore, as a means for solving this problem, Japanese Patent Publication No. 63-10100 discloses a technique for improving the flow of excess thickness by opening an open peripheral gap between the upper and lower dies and between the body dies.

[0005]

However, in the technique disclosed in Japanese Patent Publication No. 63-10100,
When the voids are enlarged to improve the fluidity, the contact area between the preform and the molding chamber atmosphere increases,
There was a problem that the extra thickness protruding from the open peripheral void was strongly cooled. Therefore, the solidification of the preform is accelerated, and the flow is obstructed before the flow is completed.
There was a problem that the fluidity could not be improved sufficiently and the fluidity was rather deteriorated depending on the shape.

The present invention has been made in view of the above-mentioned problems of the prior art, and aims to expand the range of application of glass press molding by a flat preform by preventing excess cooling of excess thickness and ensuring fluidity. An object of the present invention is to provide a molding method and a molding apparatus for an optical element that can be manufactured.

[0007]

In order to achieve the above object, the present invention provides a method for molding an optical element by heating and softening a glass material held in a barrel die and pressing it by an upper die and a lower die. , An auxiliary mold is slidably provided on the outer periphery of the upper mold,
A step of closing the gap between the upper mold and the body mold with the heated auxiliary mold at the start of press molding of the glass material, and forming a space into which a surplus of the heated glass material during molding flows. In order to have a step of continuously forming a space corresponding to the increased amount of the extra thickness while raising the auxiliary die in response to the rise of the lower die during molding pressing to bring the auxiliary die and the extra thickness into contact with each other. Configured.

Further, the present invention is an apparatus for molding an optical element by heating and softening a glass material held in a barrel mold and pressing it by an upper mold and a lower mold, which is vertically movable around the outer periphery of the upper mold. Further, an auxiliary mold having a heater is provided, and the outer diameter of the auxiliary mold is formed so as to be in contact with the inner circumference of the body mold without any gap.

[0009]

According to the optical element molding method and molding apparatus having the above-described structure, the gap between the upper die and the barrel die is closed by the auxiliary die to interrupt the contact with the outside air, and there is a margin to flow to the outer periphery of the upper die during pressing. By preventing the meat from cooling and raising the auxiliary mold as the pressing progresses, the molding proceeds while the surplus and auxiliary mold contact each other, and the viscosity of the surplus is maintained until the molding is completed. Can be kept.

Also, by keeping the temperature of the auxiliary mold and that of the upper mold as uniform as possible by the heater provided in the auxiliary mold,
Minimizing the temperature difference between the excess thickness and the molding part, and by making the upper mold and auxiliary mold materials with similar linear expansion coefficients, the clearance between the two can be kept almost constant regardless of molding conditions.
It also has the effect of keeping the auxiliary type operation normal.

[0011]

[Embodiment 1] FIG. 1 is a vertical cross-sectional view showing a main part in Embodiment 1 of an optical element molding apparatus according to the present invention. In FIG. 1, 1 and 2 are an upper mold and a lower mold, and the upper mold 1 and the lower mold 2 are arranged so as to face each other on the same axis, and are vertically movable by a drive device (not shown). Reference numeral 3 is a barrel mold for conveying the heat-softened planar preform lens between the upper and lower molds 1 and 2.

The molding surface 1a of the upper mold 1 is formed on the outer periphery of the upper mold 1 when the glass lens 7 is pressed by the upper and lower molds 1 and 2.
Forming surface 1a at the time of press molding by closing the gap between the outer periphery and the body mold 3.
An auxiliary mold 4 is arranged to heat and keep the excess meat 8 protruding outside the outer periphery of the. The auxiliary mold 4 is provided on the outer periphery of the upper mold 1 so as to be slidable in the vertical direction separately from the upper mold 1, and the radial rattling with the upper mold 1 is minimized.
It is premised that a material having a coefficient of linear expansion close to that of the material of the upper mold 1 is selected for the purpose of ensuring the coaxiality with. further,
An R-shaped chamfer 4 a is applied to the tip of the inner diameter of the auxiliary die 4. Although not shown, the molding apparatus of this embodiment has a mechanism for vertically moving the auxiliary mold 4 and a mechanism for controlling its vertical speed. A heater 5 for adjusting the heating temperature of the auxiliary die 4 is provided on the outer periphery of the lower side of the auxiliary die 4.

A push-up ring 6 for pushing up the body die 3 is provided on the outer periphery of the lower die 2. When the glass lens 7 is press-molded, the push-up ring 6 rises integrally with the lower mold 2, and the lower mold 1 pushes up the preform lens held in the barrel mold 3 and presses it against the upper mold 1. The lens barrel 3 is moved up in accordance with the above, and the glass lens 7 (preform lens) can be always arranged in the lens barrel 3.

Next, a glass lens molding method using the molding apparatus having the above-mentioned structure will be described with reference to FIGS. 2 to 6. Figure 2
6 to FIG. 6 are views showing the positional relationship of each member in the pressing process of the glass lens by time. In the figure, 7
Reference numeral a denotes a flat preform lens used for molding the glass lens 7.

First, the barrel die 3 holding the flat preform lens 7a is heated to a softening point temperature of glass (550 to 600 ° C.).
It is heated up to and is conveyed between the upper mold 1 and the lower mold 2 (see FIG. 2).

Next, the unit of the lower die 2 and the push-up ring 6 is raised at a speed V ₂ to push up the preform lens 7a and the barrel die 3 toward the upper die 1 and the auxiliary die 4. Note that the positional relationship between the upper mold 1 and the auxiliary mold 4 so far is set so that the distal end of the auxiliary mold 4 is 4 to 5 mm (more than the medium thickness of the preform lens 7a) below the distal end of the upper mold 1 ( (See FIG. 3).

When the lower die 1 and the push-up ring 6 are further raised, the tip of the auxiliary die 4 first comes into contact with the void portion of the barrel die 3 and rises together with the barrel die 3 (see FIG. 4).

When the ascent continues, the molding surface 1a of the upper mold 1 and the preform lens 7a start to contact each other.
Then, at the same time when pressing is started between the upper die 1 and the lower die 2, the auxiliary die 4 is raised at a speed V ₄ (V ₄ > V ₂ ),
The auxiliary die 4 relatively rises from the body die 3 to separate the body die 3 from the push-up ring 4 (see FIG. 5). At this time, the speed of V ₄ is adjusted between the R-shaped chamfer 4a of the upper die 1, the body die 3 and the auxiliary die 4 in accordance with the outflow amount of the extra thickness 8 protruding from the molding surface 1a of the lower die 1 by the press. Since it is necessary to expand the created void, the volume of the molding part is reduced by the compression of the mold = the volume of the excess material outflow part is expanded.

That is, assuming that the cross-sectional area of the lower mold 2 is A ₂ and the cross-sectional area of the auxiliary mold 4 is A ₄ , A ₂ V ₂ = A ₄ (V ₄ −V ₂ ). Therefore, it sets the _{V 4 = V 2 (A 2} + A 4) / A 4. As a result, during the molding pressurization in FIG. 5 (while the surplus 8 is generated, the auxiliary mold 4 is raised at the speed V ₄ )
The space surrounded by the upper mold 1, the body mold 3, and the auxiliary mold 4 is in a sealed state.

Next, when the pressing is completed, the auxiliary mold 4 is sufficiently lifted from the glass lens 7 to cool the molded glass lens 7 this time (see FIG. 6). At this time, the ascending speed V of the auxiliary mold 4 may be increased so as not to interfere with cooling. Finally, after the molding is completed and the lower mold 2 and the push-up ring 6 are lowered, the auxiliary mold 4 is returned to the state shown in FIG.
The molding cycle of the glass lens 7 is completed.

[0021]

[Embodiment 2] FIG. 7 is a vertical cross-sectional view showing the main part of Embodiment 2 of the optical element molding apparatus according to the present invention. In order to simplify the processing of the auxiliary mold 10 provided on the outer periphery of the upper mold 1, the molding apparatus of the present embodiment replaces the R-shaped chamfer 4a applied to the auxiliary mold 4 of the first embodiment with the auxiliary mold. A flat chamfer 10a is formed at the tip of the inner diameter of 10.
Other configurations are the same as those in the first embodiment. The molding method and operation of the glass lens 7 are the same as those in the first embodiment (see FIGS. 2 to 6).

[0022]

[Embodiment 3] FIG. 8 is a vertical cross-sectional view showing the main parts of Embodiment 3 of the optical element molding apparatus according to the present invention. In the molding apparatus of this embodiment, a band-shaped recess 16 is provided around the outer periphery of the auxiliary mold 15 arranged on the outer periphery of the upper mold 1, and the auxiliary mold 1 is placed in the recess 16.
The heater 5 for heating and controlling the temperature of the heater 5 is arranged to prevent the heater 5 from being displaced. Other configurations are the same as those in the first embodiment. The molding method and operation of the glass lens 7 are the same as those in the first embodiment (see FIGS. 2 to 6).

[0023]

As described above, according to the method and apparatus for molding an optical element of the present invention, there is a large amount of deformation such as molding by a flat preform and a large amount of excess thickness is generated, and the thickness of the edge wall is large. It is possible to perform stable molding even in the case of molding in which the thickness is thin and the fluid portion with excess thickness is narrow.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part in a first embodiment of an optical element molding apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a step of conveying a flat preform between upper and lower molds in Example 1 of the method for molding an optical element according to the present invention.

FIG. 3 is a vertical cross-sectional view showing a step of lifting a flat surface preform with a lower mold in Example 1 of the method for molding an optical element according to the present invention.

FIG. 4 is a vertical cross-sectional view showing a step of bringing the auxiliary mold and the body mold into contact with each other in Example 1 of the method for molding an optical element according to the present invention.

FIG. 5 is a vertical cross-sectional view showing a step of press-molding a flat preform in Example 1 of the method for molding an optical element according to the present invention.

FIG. 6 is a vertical cross-sectional view showing a step of separating the auxiliary mold from the glass lens in Example 1 of the method for molding an optical element according to the present invention.

FIG. 7 is a vertical cross-sectional view showing a main part in a second embodiment of an optical element molding apparatus according to the present invention.

FIG. 8 is a vertical cross-sectional view showing the main parts of a third embodiment of an optical element molding apparatus according to the present invention.

[Explanation of symbols]

 1 Upper mold 2 Lower mold 3 Body mold 4, 10, 15 Auxiliary mold 5 Heater 6 Push-up ring 7 Glass lens 7a Plane preform

Claims (2)

[Claims] 1. A method of molding an optical element by heating and softening a glass material held in a barrel mold and pressing it with an upper mold and a lower mold, wherein an auxiliary mold is slidably provided on the outer periphery of the upper mold,
A step of closing the gap between the upper mold and the body mold with the heated auxiliary mold at the start of press molding of the glass material, and forming a space into which a surplus of the heated glass material during molding flows. A step of continuously forming a space corresponding to the increased amount of the extra thickness while raising the auxiliary die in response to the rise of the lower die during press molding to bring the auxiliary die and the extra thickness into contact with each other. A method for forming a featured optical element. 2. An apparatus for molding an optical element by heating and softening a glass material held in a barrel mold and pressing it with an upper mold and a lower mold, the heater being movable vertically in the outer periphery of the upper mold. An apparatus for molding an optical element, characterized in that an auxiliary die having the above is provided, and the outer diameter of the auxiliary die is in contact with the inner circumference of the body die without a gap.