JPS61242920A - Molding device for lens - Google Patents

Abstract

PURPOSE:To the titled device capable of producing high precision lens, tolerating variability of material volume in a large range, eliminating centering operation, wherein coefficients of expansion of a barrel mold to lens material and of barrel mold holder are set at given values and an excess glass relief part is formed. CONSTITUTION:The glass lens material 10 is fed to the through hole 3 of the barrel mold 2, the upper mold 5 is engaged with the barrel mold, and the barrel mold holder 6 is heated to soften the lens material 10. The upper mold 5 is lowered and the lens material 10 is pressed and molded into a desired shape. The molded lens is annealed to complete the glass lens 1. Release is made easy and shape precision lens face can be raised by making a coefficient of the barrel mold 2 smaller than that of the lens material 10 and a coefficient of expansion of the barrel mold holder 6 larger than that of the lens material 10. An excess glass relief part is formed by finishing chamfering in the tapered state 5A at the outer edge part of the molding face of the mold 5 and a product with fixed thickness is obtained by prescribing the lowering position of the upper mold 5 by the top of the barrel mold holder 6 even if variability of volume of the glass material 10 is large.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for molding lenses, such as camera lenses, used in optical equipment.

Conventional technology Conventionally, as a glass lens molding device, for example,
As proposed in Japanese Patent No. 38126, a method is used in which a glass lens material heated to a predetermined temperature is pressed and molded using a pair of molds.

However, in the case of such a device, the axes of the molds that make up the lens surfaces must be precisely aligned, and the molds must be aligned so that the lens surfaces are not tilted, that is, the optical axes of the lenses are aligned. It must be assembled and configured with precision.

Furthermore, unless the volume of the supplied glass lens material is stabilized with high precision, the lens thickness or lens surface shape cannot be accurately obtained, and predetermined optical performance such as focal length cannot be obtained.

Furthermore, if the volume of the glass lens material supplied is larger than the volume required for the molded lens, even if the desired lens thickness and lens surface shape are obtained, the excess lens material will protrude toward the outer circumference of the mold, and after the lens is molded, the lens A centering process is required to make the outer diameter uniform. Centering work requires a large number of man-hours and increases costs, and is also undesirable because there is a high risk of damaging the lens surface during the work process.

Problems to be Solved by the Invention The present invention solves the above-mentioned conventional drawbacks. It allows variation in the volume of supplied lens material within a wide range, eliminates the need for centering work after lens molding, and improves the lens surface. The purpose is to improve shape accuracy and alignment accuracy of lens optical axes.

Means for Solving the Problems In order to satisfy the above object, the glass lens molding apparatus of the present invention includes a mold, a mold that fits into the mold, and a mold holder that holds the mold. , the expansion coefficient of the mold is smaller than the expansion coefficient of the lens material, and the expansion coefficient of the mold holder is larger than the expansion coefficient of the lens material, and an excess glass escape is provided on at least one lens surface side of the mold. It has a structure in which a section is formed.

Effect of the Invention The present invention uses the above-mentioned means to control the misalignment and inclination of the axis of the mold by the mold, and also causes the mold holder to shrink more than the shrinkage amount of the glass lens due to the difference in expansion coefficient between the lens material and the mold holder. However, during the molding process, the upper mold always presses the lens material, making it possible to obtain a highly accurate lens surface shape and a stable lens thickness. Further, by allowing the excess glass to flow into a recess provided on the lens mold surface side of the mold and regulating the outer diameter of the lens with the mold, centering work is no longer necessary.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a front view of the main parts showing the concept of the apparatus of the present invention, and only the molded part is shown in cross section.

FIG. 2 shows a sectional view of the mold, the mold holder, and the mold that fits into the through hole or mold cavity of the mold.

In FIGS. 1 and 2, a mold 2 is made of a predetermined ceramic material or the like, and has a through hole 3 disposed at its axis.

The through hole 3 serves as a cavity for molding the glass lens material 1o, such as a sphere, into a desired lens shape, and also maintains the upper mold 5 and lower mold 4, which are fitted through the openings at both ends, in a predetermined positional relationship, that is, the molding. It has a function of keeping the axis misalignment and inclination of the molds 4 and 5 within a desired precision.

In the embodiment shown in FIG. 2, the lower die 4 is fitted in advance into the lower end of the through hole 3 with an extremely small clearance. The mold 2 is integrally held in a mold holder 6 so as to surround the outer peripheral portion and the lower mold 4.

In FIG. 2, 17 rings 9 are used and arranged so that the end surface of the mold 2 is located at a position recessed by a predetermined dimension from the open end of the mold holder 6. The upper mold 6 has 7 ridges 79 parts 6B, and is inserted from the other open end of the through hole 3 in the direction of the arrow to shape the softened glass lens material 1o heated to a predetermined temperature into a desired lens shape. Shape. The insertion depth of the upper mold is naturally determined by the seven lens portions of the upper mold 5 coming into contact with the upper surface of the mold holder 6. That is, the desired thickness of the molded glass lens can be arbitrarily set by defining the thickness of the mold holder 6.

Note that, for the purpose of releasing the mold from the glass lens after molding, the coefficient of expansion of the members constituting the mold 2, such as ceramics, is made smaller than the coefficient of expansion of the lens material 10.

Further, the expansion coefficient of the mold holder 6 made of a metal member such as stainless steel is made larger than the expansion coefficient of the lens material 10. The reason why the expansion coefficient of the mold holder is made larger than that of the lens material is to obtain the desired precision of the lens surface shape.

That is, when the softened lens material 1o is press-molded with the upper mold 6, the lowering position of the upper mold 6 is regulated by the upper surface of the mold holder 6. When the upper mold comes into contact with the upper surface of the mold holder, cooling of the molded lens is started while maintaining the pressure of the upper mold, and the molded lens is cooled down to the lens take-out temperature of around 3oo"c.It is not necessary to cool the molded lens. This is nothing but cooling the mold holder 6 and the mold 2, and by making sure that the amount of contraction of the mold holder 6 due to temperature drop is greater than the amount of contraction of the molded lens, the upper mold is always attached to the lens during the molding process. A pressing force of is applied.

The upper mold 5 and the lower mold 4 are made of a predetermined ceramic material or the like and formed into a predetermined cylindrical shape, and one end surface of each mold is finished in a mirror-like state so that it is perpendicular to the mold axis and has a predetermined lens surface shape. There is.

In the embodiments of the present invention, the mold surfaces were respectively concave in order to obtain convex lenses.

The outer diameters of the cylindrical parts of the upper mold 6 and the lower mold 4 are configured to be larger than the effective diameter of the molded glass lens 1 by a predetermined amount, and the mold surface side of the upper mold 6 has an outer edge located outward from the effective diameter. The part is finished with a tapered chamfer to a predetermined size. The chamfered portion 5A becomes a space into which excess glass of the glass lens flows. During the molding process, a part of the cylindrical part of the mold 4.6 is made into a stepped shape, and L-shaped communication holes 7A and 7B are formed, respectively, for the purpose of releasing gas from the cavity.

The hole 8 provided in the body-shaped holder is also for the purpose of gas release.

The die set 16 shown in FIG. 1 includes an upper plate 11 a lower plate 12. Guide boss 14. The upper plate 11 is configured by a driving cylinder 13, and the upper plate 11 slides by a predetermined stroke amount in the force directions of arrows x and x'. Furthermore, a cartridge heater 16 and a temperature sensor (not shown) are embedded in the upper plate 11 and lower plate 12, and heat each plate to a predetermined temperature that softens the glass lens material.

Next, the above-mentioned die set 15. Mold 2 and body mold holder 6
, the process of molding a desired molded glass lens using the upper mold 5 and the lower mold 4 will be explained.

First, insert the spherical glass lens material 1 into the through hole 3 of the mold 2.
0 is supplied, and then the upper mold 6 is fitted into a predetermined position. Thereafter, the barrel-shaped holder 6 is heated to a predetermined heating device such as a tunnel furnace,
The glass lens material is heated to a softened state where it can be molded by heating using means (not shown) such as on an open or hot plate.

Thereafter, the body mold holder 6 heated to a predetermined temperature is placed on the lower plate 12 of the die set 16, and the upper plate 11, which had been located at the two-dot chain line position, is lowered to the predetermined position shown by the solid line. The glass lens material 1o is press-molded into a predetermined shape through the press. After that, when the seventh rank part 6B of the upper mold comes into contact with the upper surface of the body mold holder 6, the heater 16 is turned off.
The molded glass lens 1 is completed by removing the barrel-shaped holder whose temperature has cooled to around 300° C. from the die set, and then slowly cooling the molded lens to room temperature.

In the above embodiment, the supplied glass lens material 1o
It goes without saying that the volume of is slightly smaller than the volume of the molding cavity formed by the through hole 3 and the molding molds 4 and 6, and the variation range of the volume of the glass lens material is also determined on the molding lens surface side of the upper mold 5. The same applies to the case where the volume is within the volume of the chamfered portion 6A.

Effects of the Invention As mentioned above, by absorbing the volume variation of the glass lens material with the chamfered part of the mold, and by setting the Ruder's expansion coefficient to a predetermined value in the mold, the thickness of the molded lens, the accuracy of the lens surface shape, and the optical axis can be improved. It is possible to obtain a lens having a high degree of coincidence, etc., with high precision.

[Brief explanation of drawings]

FIG. 1 is a front view of essential parts showing the concept of the apparatus of the present invention, and FIG. 2 is a sectional view of a mold and a body boulder constituting the apparatus of the present invention, and a mold that fits into the mold. 1... Molded glass lens, 2... Side temperature, 3. Through hole, 4... Bottom mold, 6...
・Upper mold, tsA...Curved chamfered υ part, 5B...Flange part, 9...Retaining ring, 13...Drive cylinder, 10...Glass Lens material, 11
...Top plate, 12...Bottom plate, 16...Die set, 16...Cartridge heater.

Claims (2)

[Claims] (1) A body mold, a mold that fits into the body mold, and a body holder that holds the body mold, the expansion coefficient of the body mold being smaller than the expansion coefficient of the lens material; A lens molding device characterized in that the expansion coefficient is larger than the expansion coefficient of the lens material. (2) A lens molding apparatus according to claim 1, characterized in that a desired lens thickness can be obtained in a state in which the flange portion of the mold is in contact with the main plane of the body holder. .