JPH07215721A - Lens molding equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To eliminate the need for centering work after lens molding, and to improve the accuracy of the lens surface shape and the accuracy of matching the lens optical axes. A pair of lens molding dies 4 and 5 and a barrel mold 2 slidably holding the lens dies 4 and 5 are provided, and the barrel mold 2 includes a replenishing barrel mold portion 9 having different expansion coefficients. Configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens forming device for a lens such as a camera lens used in optical equipment.

[0002]

2. Description of the Related Art Conventionally, as a glass lens molding apparatus, a method of press-molding a glass lens material heated to a predetermined temperature with a pair of molding dies has been used, for example, as proposed in Japanese Patent Publication No. 54-38126. There is.

However, in the case of such an apparatus, the respective molding die axes constituting the lens surfaces are accurately aligned with each other, and the respective lens surfaces are not inclined, that is, the lens optical axes are aligned with each other. Must be accurately assembled and configured.

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

Further, if the volume of the glass lens material to be supplied is made larger than the volume required for the molding lens, the lens thickness dimension and the lens surface shape accuracy can be obtained as desired, but the extra lens material protrudes in the outer peripheral direction of the molding die. After the lens is molded, a centering process for finishing the outer diameter of the lens to be constant is required. The centering work requires a large number of man-hours and increases the cost, and there is a possibility that the lens surface may be damaged in the working process, which is not preferable.

Further, Japanese Patent Laid-Open No. 5-270845,
Japanese Unexamined Patent Publication (Kokai) No. 5-286727 and the like have been proposed, and the separation of the barrel mold portion and the molded lens and the lens outer diameter are described. However, no mention is made of lens surface shape accuracy.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by allowing a large range of variations in the volume of lens material to be supplied, eliminating the need for centering work after lens molding, and It is an object of the present invention to provide a lens molding device that improves the lens surface shape accuracy and the lens optical axis matching accuracy.

[0008]

In order to solve the above-mentioned problems, a lens molding apparatus of the present invention comprises a lens molding die pressing means which can be contacted and separated, a pair of lens molding dies for forming a lens surface,
It is composed of a barrel mold that slidably holds the lens mold, and a pedestal that fits the barrel mold into the recess, and the barrel mold is configured to have a joint portion having different expansion coefficients. Further, the expansion coefficient of the joint portion is larger than that of the lens material, or the contraction amount of the joint portion is larger than that of the lens material. Also,
A surplus glass escape portion is formed on at least one lens surface side of the molding die.

[0009]

According to the present invention, the construction of the lens molding apparatus is extremely simple and the axial misalignment and inclination of the molding die are regulated by the barrel die, and the expansion coefficient between the lens material and the additional barrel die portion is made by the above construction. Due to the difference between the two, the body part of the additional body contracts more than the amount of contraction of the glass lens. As a result, in the process from molding to cooling, the upper mold always presses the lens material to obtain a highly accurate lens shape and a stable lens thickness dimension. Further, a surplus of glass is caused to flow into a concave portion provided on the lens molding surface side of the molding die, and the outer diameter of the lens is regulated by the barrel die, thereby eliminating the need for centering work.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens molding apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a main part showing the concept of a lens molding apparatus according to the present invention, in which only the molding part is shown in a sectional shape. FIG. 2 shows a body mold having a replenishing body part disposed on the upper end side, a forming mold fitted in a through hole of the body mold, that is, a forming cavity, and a pedestal formed by fitting the body mold in a recess. A sectional view is shown.

In FIGS. 1 and 2, a barrel die 2 which constitutes a barrel portion is made of a super hard member such as a predetermined ceramic material, for example, tungsten carbide (hereinafter referred to as WC), and a through hole 3 is formed in an axial center thereof. Are installed. Also, the body mold 2
The expansion coefficient is set to be smaller than the expansion coefficient of the glass lens material 10. The through hole 3 serves as a cavity for molding the glass lens material 10 having a spherical shape into a desired lens shape, and a predetermined lens surface forming upper die 5 and lower die 4 which are slidably fitted through openings at both ends are predetermined. It has a function of maintaining the positional relationship, that is, keeping the axial misalignment and inclination of the molding dies 4 and 5 within desired accuracy. In the embodiment shown in FIG. 2, the lower mold 4 is fitted in advance to the body mold 2 at the lower end of the through hole 3 with a very small clearance. Body type 2
Has a body part 9 removably fitted to its upper end. The additional body portion 9 is made of a metal member such as stainless steel or a ceramic member to have a predetermined concave portion, and its expansion coefficient is set to be larger than that of the glass lens material. Specifically, temperature 5
From the amount of lens shrinkage when the pressure-molded lens is cooled near 00 ° C. and lowered to a take-out temperature near 300 ° C., the replenishment barrel mold part 9 is about 500 ° C. to about 300 ° C.
The shrinkage amount is set to increase during the temperature drop to ℃. As a matter of course, the amount of contraction between the two is the product of the lens thickness dimension, the temperature difference, and the lens material expansion coefficient, and the product of the axial length dimension of the add-on barrel mold section 9, the temperature difference, and the expansion coefficient. Is calculated by As described above, by making the amount of shrinkage of the replenishing barrel mold portion 9 surely larger than the amount of shrinkage of the molded lens, a pressing force always acts on the lens in the process from molding to cooling. As described above, the expansion coefficient of the member forming the body mold 2, for example, a ceramic member such as WC, is set to be smaller than the expansion coefficient of the glass lens material 10 for the purpose of releasing from the molded glass lens. With this configuration, the outer diameter dimension of the molded glass lens 1 becomes smaller than the inner diameter dimension of the barrel mold 2 near the lens removal temperature of 300 ° C.

As means for integrating the body die 2 and the replenishing body die portion 9 with each other, there is a clearance clearance and a removable clearance fit, as well as a press fit fitting with a tight margin, or an integration by welding. It may be implemented arbitrarily. The pedestal 6 has a concave sectional shape, and the body mold 2 is detachably fitted in the concave portion. The members are made of inexpensive materials such as stainless steel and ceramics. The expansion coefficient is not particularly limited. This pedestal 6 prevents the lower mold 4 from coming off the body mold 2.

The upper mold 5 has a flange portion 5B, is inserted from the other opening end of the through hole 3 in the direction of the arrow, and heats the glass lens material 10 which has been heated to a predetermined temperature to a desired lens shape. Press molding. The insertion depth of the upper die 5 is naturally determined by the flange portion 5B of the upper die 5 contacting the upper end surface of the add-on barrel die portion 9. That is, the desired glass lens thickness dimension can be arbitrarily set by defining the total thickness dimension (that is, the total height dimension) of the barrel die and the additional barrel die portion. Further, the upper mold 5 and the lower mold 4 are formed by processing a predetermined ceramic material or the like into a predetermined cylindrical shape, and one end surface of each mold is a mirror surface so as to have a predetermined lens surface shape orthogonal to the mold axis. It is finished in a state. In the embodiment of the present invention, the mold surface shape is concave in order to obtain a convex lens. The outer diameter of the cylindrical portion of the upper mold 5 and the lower mold 4 is configured to be larger than the effective diameter of the molded glass lens 1 by a predetermined amount, and the outer peripheral portion of the upper mold 5 located outside the effective diameter on the molding die surface side. Is chamfered in a tapered shape to a predetermined size. The chamfered portion 5A becomes a space into which surplus glass of the glass lens flows. Further, the upper die 5 and the lower die 4 have a stepped shape in a part of the column and have L-shaped communication holes 7A and 7B for the purpose of gas escape in the cavity or replacement with nitrogen gas in the molding process. Each is perforated. The holes 8 formed in the pedestal 6 are also intended for gas escape.

The die set 15 shown in FIG. 1 is an upper plate 1
1, the lower plate 12, the guide post 14, and the drive cylinder 13, the upper plate 11 slides by a predetermined stroke in the directions of arrows X and X ′ by the drive cylinder 13. That is, the upper plate 11 abuts and separates to press the molding die (upper die 5). Further, the cartridge heater 16 and the temperature sensor (not shown) are provided on the upper plate 1.
1, embedded in the lower plate 12, each plate is heated to a predetermined temperature for softening the glass lens material 10.

Next, a process for molding a desired molded glass lens by using the above-mentioned die set 15, the barrel mold portion (the barrel mold 2 and the additional barrel mold portion 9), the upper mold 5 and the lower mold 4. explain. First, the spherical glass lens material 10 is supplied into the through hole 3 of the body mold 2, and then the upper mold 5 is fitted in a predetermined manner. This is heated to a softened state in which the glass lens material 10 can be molded, using an arbitrary means such as a predetermined heating device such as a tunnel furnace, an oven, a hot plate, and a high frequency heating device. Then, the barrel mold part (the glass lens material 10 and the upper mold 5 are set) that has risen to a predetermined temperature is placed on the lower plate 12 of the die set 15,
The upper plate 11 located at the position indicated by the chain double-dashed line is lowered to a predetermined position indicated by the solid line, and the glass lens material 10 is press-molded through the upper mold 5 in a predetermined manner. After that, when the upper mold flange portion 5B is added and comes into contact with the upper end surface of the barrel mold portion 9, the heater 16 is turned off, the temperature is lowered to around 300 ° C., and then the barrel mold portion is removed from the die set, and the molded lens is kept at room temperature. The molded glass lens 1 is completed by slowly cooling to.

Needless to say, in the above embodiment, the volume of the glass lens material 10 supplied is slightly smaller than the volume of the molding cavity formed by the through hole 3 and the molding dies 4 and 5. The variation range of the glass lens material volume is also set to be within the volume of the chamfered portion 5A arranged on the molded lens surface side of the upper mold 5.

Further, the position where the replenishing body part is arranged is also arbitrary. As in the above-mentioned embodiment, the configuration is not limited to the case where it is arranged at the upper end portion of the body die, but the body die portion 39 may be integrally provided by adding to the lower end portion of the body die 32 as shown in FIG. May be. Of course, it may be arranged at the center of the body. In the case of arranging in the central portion, it is desirable to integrate the replenishing barrel mold portion and the barrel dies arranged above and below it by means such as welding or press fitting so that the handling work of the barrel mold portion is ready. In the case of integrally arranging the additional trunk body portion 39 on the lower end portion of the trunk die 32, a gap G is provided between the lower end surface of the trunk die 32 and the bottom surface of the recess of the additional trunk die portion 39 in a predetermined size. The shrinkage amount of the total height L of the replenishing barrel mold portion 39 is set to be surely larger than the shrinkage amount of the molded glass lens. Although FIG. 3 shows a configuration in which the pedestal is omitted, it goes without saying that a configuration including a pedestal may be provided.

Further, as shown in FIGS. 4 and 5, when arranging the replenishing barrel mold portions 49, 59 on the upper end surface side of the barrel mold 2, the height dimensions L1, L2 and the gap (spacing) dimension G1 or G2 are set. It may be set arbitrarily. That is, in FIG. 4, the abutting position between the body mold 2 and the replenishing body mold part 49 is represented by
And a bottom surface 41 of the additional body portion 49 and a predetermined gap G1 between the lower end surface side of the additional body portion 49 and the step portion 42 of the body 2 The shrinkage amount of the dimension L1 is set to be surely larger than the shrinkage amount of the molded glass lens. Further, in FIG. 5, the abutting position between the body die 2 and the extension body portion 59 is the lower end surface of the step portion 52 of the body die 2 and the body portion 59, and the upper end surface of the body die 2 and the extension body portion 59. A gap (spacing) G2 is provided between the mold part 59 and the bottom surface 51 of the concave part to have a predetermined size, and the additional body part 5 is added.
It is set so that the shrinkage amount of the total height dimension L2 of 9 is certainly larger than the shrinkage amount of the molded glass lens. As a matter of course, when the total height dimensions and the materials of the additional trunk body portions 49 and 59 are the same (the expansion coefficients are the same), the amount of contraction of the additional trunk body portion 59 in FIG. It can be set larger than the amount of contraction. In this way, by properly selecting the additional body portion and the contact portion where the body portion abuts, that is, the additional body portion 49, 59 is detachably fitted to the body die 2 and the height dimension is increased. By setting and selecting the relationship between L1 and L2 and the gap (skimmer) dimension G1 or G2 to a predetermined value, it is possible to cope with the contraction amount of the molded glass lens within a large range in which the contraction amount of the barrel portion is extended. Further, the present invention can be applied to the case where different kinds of lens materials are molded without largely changing the heat capacity of the lens molding apparatus including the pair of molding dies, the body mold, and the pedestal. The fact that the heat capacity of the lens molding device is approximately equal is extremely convenient for continuously performing glass lens molding, and the heating conditions can be changed each time,
There is no need to interrupt the molding operation once.

[0019]

As described above, the volume variation of the glass lens material is absorbed by the chamfered portion of the molding die, and the outer diameter of the lens is made constant by the body portion, so that the centering work is unnecessary. Furthermore, by setting the expansion coefficient of the barrel mold to be smaller than the expansion coefficient of the glass lens material and setting the expansion coefficient of the joint barrel mold to be large, the molded lens thickness dimension, lens surface shape accuracy, optical axis matching accuracy, etc. It is possible to obtain a lens having a high precision. Furthermore, by setting and selecting the contact position and the gap between the barrel mold and the replenishing barrel mold part in a predetermined manner, it is possible to easily mold different lens materials without significantly changing the heat capacity of the lens molding device. It will be possible.

[Brief description of drawings]

FIG. 1 is a front view of a main part showing the concept of a lens molding apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a barrel mold, a molding die fitted to the barrel mold, and a pedestal that constitute the device of the present invention.

FIG. 3 is a front view of a main part showing the concept of a lens molding device according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a barrel die, a molding die fitted to the barrel die, and a pedestal according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a barrel mold, a molding die fitted to the barrel mold, and a pedestal according to another embodiment of the present invention.

[Explanation of symbols]

 1 Molded glass lens 2,32 Body type 3 Through hole 4,34 Lower model 5,35 Upper model 5A Chamfered section 5B Flange section 6 Pedestal 9,39,49,59 Joint body section 11 Upper plate 12 Lower plate 13 Drive cylinder 14 Guide Post 15 Die Set 16 Heater 41, 51 Recessed Bottom 42, 52 Step

Claims (11)

[Claims] 1. A lens comprising a pair of lens molds and a barrel mold for slidably holding the lens molds, wherein the barrel molds have additional barrel mold parts having different expansion coefficients. Molding equipment. 2. The abutting position between the trunk die and the extension body portion is the upper end surface of the body die and the bottom surface of the recess of the extension body portion, and the lower end surface of the extension body portion and the body die. The lens molding device according to claim 1, wherein a gap is provided between the lens molding device and the step portion. 3. A contact position between the trunk die and the extension body section is the lower end surface of the step section and the extension body section, and the bottom surface of the recess of the extension body section and the body section. The lens molding apparatus according to claim 1, wherein a gap is provided between the lens molding apparatus and the upper end surface of the lens molding apparatus. 4. The lens molding apparatus according to claim 1, wherein an expansion coefficient of the replenishing barrel mold portion is larger than an expansion coefficient of a lens material. 5. The lens forming apparatus according to claim 1, wherein the shrinkage amount of the replenishing barrel mold portion is larger than the shrinkage amount of the lens material. 6. The lens molding apparatus according to claim 1, wherein the replenishing barrel mold part is detachably fitted to the barrel mold. 7. A mold pressing means which can be contacted and separated, a pair of lens molds, and a barrel mold which slidably holds the lens molds, the barrel molds being replenishing barrel molds having different expansion coefficients. A lens forming apparatus, which is provided with a section. 8. A pair of lens molds, a barrel mold for slidably holding the lens mold, and a pedestal for fitting the barrel mold in a recess, wherein the barrel molds have different expansion coefficients. A lens forming apparatus comprising a replenishing body part. 9. The lens forming apparatus according to claim 8, wherein the expansion coefficient of the replenishing barrel mold portion is larger than the expansion coefficient of the lens material. 10. The lens molding apparatus according to claim 8, wherein the shrinkage amount of the replenishing barrel mold portion is larger than the shrinkage amount of the lens material. 11. A mold pressing means that can be contacted and separated, a pair of lens molds, a barrel mold that slidably holds the lens molds, and a pedestal that fits the barrel molds in a recess. The lens forming apparatus is characterized in that the body mold comprises additional body mold parts having different expansion coefficients.