JP2000053432A - Forming apparatus for optical glass element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming apparatus for optical glass elements which is simple in construction, short in tact time and good in production efficiently. SOLUTION: This forming apparatus for the optical glass elements constitutes a die set 18 by including a pair of forming dies 1, 2 for holding a glass blank 5 and a sleeve 3 freely slidably fitted into at least one forming die 1 and presses and forms the glass blank 5 by heating this die set 18 in an inert gaseous atmosphere, thereby heating and softening the glass blank. In such a case, the apparatus has a cooling means 9 which is disposed in the position enclosing the die set 18 and cools the die set 18 by blowing inert gas to the die set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass element forming apparatus for softening a glass material by heating and softening the glass material.

[0002]

2. Description of the Related Art In recent years, the need for aspherical lenses has been increasing in order to satisfy demands for higher performance of a single lens and reduction in the number of lenses in a lens system. Means for finishing a glass material by spherical polishing has been used for a long time to manufacture a glass lens, but manufacturing an aspherical lens by polishing is very difficult and expensive. Therefore, it has been considered to manufacture an aspheric lens by molding. However, since plastic materials that can be easily molded have optical limitations, techniques for molding glass have been actively developed. In order to mold the optical glass element, the glass and the mold are adjusted to a temperature at which the glass can be molded, generally to an appropriate temperature between the Tg point (glass transition temperature) and the Sp point (softening point temperature). There is a need. In this temperature range, the temperature generally rises to about 400 ° C. or more, depending on the type of the glass material, and most of the materials constituting the molding apparatus are significantly deteriorated.

In order to prevent this, for example, Japanese Patent Laid-Open No. 9-71
No. 425 is disclosed. FIG. 6 shows a schematic configuration diagram of a molding apparatus, and this technique will be described with reference to FIG. In FIG. 6, a heating furnace 51 is disposed in a closed molding chamber 50, air is exhausted from an exhaust port 53 in the molding chamber 50, and nitrogen gas is introduced from an intake port 52 to replace the air. By using an inert gas atmosphere, deterioration of the material constituting the molding apparatus is prevented. Also, the molding chamber 5
Outside 0, a pair of molds taken out of the molding chamber 50,
Nozzle 54 for blowing nitrogen blow to cool sleeve and mold set 55 consisting of molded optical glass element
Are arranged.

[0004]

However, the above prior art has the following problems. That is, in the above molding apparatus, it is necessary to continue heating from around room temperature to a temperature at which molding can be performed in the heating furnace 51 together with the mold set 55, and after molding, the inside of the molding chamber 50 is kept until the mold member is no longer oxidized. Therefore, there is a disadvantage that the tact time is long and the production efficiency is poor. A nozzle 54 for ejecting nitrogen blow in this molding apparatus cools after being no longer oxidized outside the molding chamber 50, that is, the mold set 55 is taken out of the molding chamber 50 filled with an inert gas. If the mold set 55 is quickly taken out of the atmosphere of the inert gas before cooling to a temperature at which the mold members and the like are not oxidized for cooling, the mold members and the like deteriorate due to oxidation. In the above molding apparatus, the heating furnace 5
Since the inside of the furnace 1 is not cooled rapidly, the supply amount of nitrogen gas is increased, so that the entire inside of the molding chamber 50 covering the entire heating furnace 51 is cooled. Was required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an optical glass having a simple structure, a short tact time and a high production efficiency. An object of the present invention is to provide an apparatus for forming a device.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1, 2 or 3 is characterized in that a pair of molding dies for holding a glass material and at least one of the molding dies are slidable. An optical glass element forming apparatus comprising: a mold set comprising: a sleeve that fits into the mold material; and heating the mold set in an inert gas atmosphere to heat soften the glass material and press-mold the glass material. And a cooling means for cooling the mold set by spraying an inert gas onto the mold set.

In the apparatus for molding an optical glass element according to the first, second or third aspect of the present invention, after press molding, the mold set is blown with an inert gas from a cooling means provided at a position surrounding the mold set. The mold is cooled, and is quickly cooled to a temperature at which the mold members constituting the mold set do not oxidize. In the apparatus for molding an optical glass element according to the second aspect of the present invention, in addition to the above operation, the cooling means is formed by an annular pipe, and a plurality of inert gas outlets are provided on the annular inner peripheral surface. Therefore, the mold set is uniformly cooled from the 360-degree direction. In the optical glass element forming apparatus according to the third aspect of the present invention, in addition to the above-described operation, the cooling unit includes a retracting unit that retracts out of a heating area of a heater that heats the mold set at least during molding of the optical glass element. Therefore, it is arranged at a position surrounding the mold set only when the mold set is cooled, and retreats out of the heating area of the heater when the mold set is heated.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention,
Although the description will be made by taking the formation of a concave meniscus lens as an example, the present embodiment is also applied to the formation of an optical glass element such as a convex meniscus lens, a biconcave lens, a biconvex lens, a plano-concave lens, a plano-convex lens, etc. can do. Hereinafter, specific embodiments will be described.

(Embodiment 1) FIGS. 1 to 3 show Embodiment 1, FIG. 1 is a longitudinal sectional view of an optical glass element forming apparatus, FIG. 2 is a perspective view of a blow pipe, and FIG. FIG.

In FIG. 1, a molding apparatus for an optical glass element mainly includes a heating furnace 20 provided in a molding chamber 19 formed in a closed structure, and a mold set 18 inserted into and removed from the heating furnace 20. And a drive mechanism 21 that moves up and down. A plurality of annular infrared heaters 6 are provided in the heating furnace 20. The quartz glass tube 7 is disposed inside the infrared heater 6 and at the center on the lower plate 23 constituting the molding chamber 19. In addition, the infrared heater 6
An outer cylinder 8 made of a stainless steel plate is disposed outside the box, and the inside is coated with gold to reflect infrared rays. An upper plate 22 is fixed to the upper ends of the quartz glass tube 7 and the outer cylinder 8 so as to substantially seal the inside of the heating furnace 20. An outlet 17 for ejecting nitrogen gas, which is an inert gas, into the heating furnace 20 to form an inert gas atmosphere (nitrogen purge) is provided on the upper surface of the lower plate 23. By making the inside of the heating furnace 20 an inert gas atmosphere, deterioration of the structural members constituting the heating furnace 20 and the mold members of the mold set 18 are suppressed.

The mold set 18 includes an upper mold 1 that is one of a pair of molding dies, a lower mold 2 that holds the glass material 5 between the upper mold 1 that is the other of the pair of molding dies, Mold shaft part 2a
(See FIG. 3), and the upper mold 1 and the lower mold 2 are fitted to the outer periphery of the holder 4 and the outer periphery of the flange 1a of the upper mold 1 (see FIG. 3). Sleeve 3 for concentricity
It is composed of The holder 4 has a step 4a on the inside.
(See FIG. 3), and a glass material 5
Is placed. The holder 4 holds the glass material 5 before molding, and the mold shaft portion 2a of the lower mold 2 by a transport device (not shown).
The glass material 5 is positioned at a position above the molding surface of the lower mold 2 (see FIG. 3). After molding,
After the holder 4 is taken out together with the lower mold 2, the optical glass element formed by a transfer device (not shown) is carried out from the lower mold 2.

An upper shaft 10 is provided above the mold set 18, and the upper shaft 10 is connected to a cylinder 16 fixed to an upper wall of a molding chamber 19 and is driven up and down. Upper shaft 10
Is connected to a hose and a vacuum device (not shown), and the upper mold 1 is connected to the lower end of the upper shaft 10 while the mold set 18 is being heated.
Are fixed by vacuum suction. During molding,
The upper shaft 10 lowers the upper mold 1 by the pressing force of the cylinder 16 and press-molds the glass material 5 with the lower mold 2. A slight gap is formed between the upper shaft 10 and the upper plate 22 of the heating furnace 20 so that nitrogen gas flows out of the heating furnace 22 into the molding chamber 19.

Below the mold set 18, a drive mechanism 21 for vertically moving the mold set 18 is provided. The lower shaft 11 is disposed above the driving mechanism 21, and the mold set 18 is placed on the lower shaft 11. The lower shaft 11 is attached to the lower shaft base 12, and when the mold set 18 is raised, the lower plate 23 of the molding chamber 19 is moved.
And a slight gap is formed between them so that the nitrogen gas in the heating furnace 20 slightly flows out to the outside. The lower shaft base 12 is vertically movably guided by a bush 13 fitted to a plurality of columns 15 supporting a molding chamber 19. Further, the lower shaft base 12 is driven up and down by a driving device such as a cylinder (not shown). The drive mechanism 21 mounts the mold set 18 before molding, ascends and carries the mold set 18 into the heating furnace 20, and descends after molding to carry the mold set 18 out of the heating furnace 20.

At a position surrounding the mold set 18 in the heating furnace 20, a blow pipe 9 as cooling means is provided. In FIG. 2, the blow pipe 9 is an annular pipe 9A.
And three equally arranged supply pipes 9B for supplying nitrogen gas to the annular pipe 9A. In order to uniformly cool the mold set 18 in the circumferential direction, a plurality of outlets 24 are formed in the inner periphery of the annular pipe 9A, and the cooling effect of the blown nitrogen gas allows the mold set 18 to be cooled. The resulting circumferential temperature distribution is minimized. As shown in FIG. 1, one of the three supply pipes 9 </ b> B is also used as a push-up pipe of a cylinder 14 as a retracting means attached to the lower plate 23 of the molding chamber 19. Each supply pipe 9B is connected to a hose and a nitrogen gas supply device (not shown). The blow pipe 9 can be moved up and down by the cylinder 14 in the direction of the arrow, and when the mold set 18 is not cooled, the material of the blow pipe 9 is prevented from deteriorating due to the heat of the infrared heater and the mold set 18 is irradiated. In order to prevent an increase in tact time by shielding infrared rays, it is possible to retreat to the bottom of the heating furnace 20.

The upper mold 1, the lower mold 2 and the sleeve 3 constituting the mold set 18 are made of tungsten carbide (WC), and the holder 4 is made of a tungsten alloy. The glass material 5 to be molded is PBH6 manufactured by OHARA
Consists of The upper shaft 10 and the lower shaft 11 constituting the forming apparatus are made of silicon carbide (SiC), and the blow pipe 9 is made of a hollow pipe made of stainless steel.

Next, a method of forming an optical glass element using the above-described forming apparatus will be described. First, outside the molding equipment,
As shown in FIG. 3, a glass material 5 is provided on the step 4a of the holder 4.
And the holder 4 is fitted to the mold shaft 2a of the lower mold 2. Next, the sleeve 3 is fitted to the holder 4, and the outer periphery of the flange 1 a of the upper mold 1 is fitted to the inner diameter of the sleeve 3 to complete the assembly of the mold set 18. Next, the mold set 18 is placed on the lower shaft 11, and the lower shaft base 12 is lifted and carried into the heating furnace 20. At this time, mold set 1
The upper die 1 in 8 is vacuum-sucked on the upper shaft 10, and the molding surface of the upper die 1 is not in contact with the glass material 4. Next, a nitrogen gas is supplied from the blowing port 17 to make the inside of the molding chamber 19 an inert gas atmosphere, and then the supply of the nitrogen gas is stopped. In this state, the annular pipe 9A of the blow pipe 9 is retracted to the bottom of the heating furnace 20. This is the preparation stage of the molding operation.

Next, the molding stage will be described. The power of the infrared heater 6 is turned on, and the heating of the mold set 18 is started.
When the temperature of the mold set 18 reaches a predetermined temperature, the upper shaft 10 is lowered by the cylinder 16 to apply a load, and the glass material 5 is pressed. When the glass material 5 is pressed to a predetermined thickness and the optical glass element is formed, the upper shaft 1 is pressed.
Then, the power of the infrared heater 6 is turned off. Then
The annular pipe 9A of the blow pipe 9 is raised to an intermediate height of the mold set 18, and nitrogen gas at room temperature (or set to a predetermined temperature) is jetted from the plurality of outlets 24 toward the mold set 18. Thereby, the upper mold 1, the lower mold 2, and the formed optical glass element in the holder 4 are cooled via the sleeve 3. When the mold set 18 is sufficiently cooled and reaches a temperature at which the mold set 18 can be taken out, the lower shaft base 12 is lowered, the mold set 18 is carried out of the heating furnace 20, and disassembled in a procedure reverse to the assembly. The molded optical glass element is taken out, and the molding operation is completed.

When the nitrogen gas for cooling is blown out from the outlet 24 of the annular pipe 9A, the holder 4 is cooled via the sleeve 3. Even when the outlets 24 are separated from each other, the temperature of the outer peripheral surface of the holder 4 is substantially equalized by cooling the sleeve 3 so that the temperature of the outer peripheral surface of the sleeve 3 becomes substantially equal. Is cooled. Then, the outer peripheral surface of the optical glass element is uniformly cooled. On the other hand, the upper and lower ends of the sleeve 3 cool the flange portion 1a of the upper die 1 and the flange portion 2b of the lower die 2, and cool the molding surfaces of the upper die 1 and the lower die 2 via the respective flange portions 1a and 2b. I do. For this reason, the cooling of the mold set 18 is efficiently performed without generating a temperature distribution.

Next, an experimental example in which an optical glass element is molded will be specifically described. In this experiment, an annular pipe 9A having a pipe diameter of 6 mm and a ring diameter of 80 mm was used, and 28 holes with a diameter of 1 mm were equally formed in the inner periphery of the ring to form the outlet 24. . The optical glass element is a concave meniscus lens having an outer diameter of 12 mm. The temperature of the upper and lower dies 1 and 2 during molding was 440 ° C., the flow rate of nitrogen gas used during cooling was 100 l / min, and the tact time required for molding was 10 minutes. Of the tact time, the time required for cooling was 3 minutes and 30 seconds.

For comparison, the test was carried out at the same temperature and the like without blowing nitrogen gas from the blow pipe 9. As a result, the tact time was 15 minutes and 20 seconds. Further experiments were conducted with the flow rate of nitrogen gas reduced to 50 l / min.
The tact time was 12 minutes. Incidentally, in any of the experiments, the molded optical glass element did not show any poor surface accuracy.

According to the present embodiment, an optical glass element can be molded with a short tact time and with high production efficiency by a molding apparatus having a simple structure. In order to cool the mold set evenly in the circumferential direction,
A plurality of outlets are provided, and the circumferential temperature distribution generated in the mold set can be minimized by the cooling effect of the blown nitrogen gas. Furthermore, since the blow pipe is moved up and down by the cylinder and can be retracted to the bottom of the heating furnace except during cooling of the mold set, it prevents material deterioration of the blow pipe due to the heat of the infrared heater, and reduces the infrared rays emitted to the mold set. It is possible to prevent an increase in tact time due to light shielding.

In this embodiment, a stainless steel hollow pipe is used as the material of the blow pipe, but the material is not particularly limited. However, a material having heat resistance is desirable.
The size, position, and number of outlets provided in the annular pipe of the blow pipe are not limited, but a larger number is desirable to promote a sufficient flow rate and uniform cooling. In addition, the materials of the upper and lower molds, the sleeve, the holder, and the like that constitute the mold set are not particularly limited. Further, although the infrared heater is used as the heat source, another heat source such as a high-frequency coil may be used.

(Embodiment 2) FIGS. 4 and 5 show Embodiment 2, FIG. 4 is a perspective view of a blow pipe, and FIG. 5 is an enlarged sectional view of an outlet of an annular pipe. This embodiment is different from the first embodiment only in the blow pipe,
Only different portions will be described, and the drawings and description of the same portions will be omitted.

In FIG. 4, the blow pipe 31 comprises an annular pipe 31A, and three equally arranged supply pipes 31B for supplying nitrogen gas to the annular pipe 31A. In order to cool the mold set 18 evenly in the circumferential direction,
As shown in FIG. 5, a plurality of outlets 32A and 32B in two rows in the upper and lower directions are formed in the inner periphery of the annular pipe 31A, and the directions of the holes are 45 degrees upward and 45 degrees downward. ing. Due to the cooling effect of the nitrogen gas blown up and down in two directions, the circumferential and axial temperature distributions generated in the mold set 18 are minimized and the cooling rate is increased by increasing the flow rate. Other configurations are the same as those of the first embodiment.

The method for forming an optical glass element in the present embodiment is the same as that in the first embodiment, and a description thereof will be omitted.

Next, an experimental example in which an optical glass element is molded will be specifically described. In this experiment, an annular pipe 31A having a pipe diameter of 6 mm and a ring diameter of 80 mm was used, and 28 holes (a total of 56 holes) each having a diameter of 0.8 mm were equally formed in two rows on the inner periphery of the ring. The holes 32A and 32B were formed by punching. The optical glass element is a concave meniscus lens having an outer diameter of 12 mm. The temperature of the upper and lower dies 1 and 2 during molding was 440 ° C., and the flow rate of the nitrogen gas used during cooling was 130 l / min. The time required for cooling out of the tact time was 2 minutes and 30 seconds. In addition,
No defects in surface accuracy occurred in the molded optical glass element.

According to the present embodiment, in addition to the effects of the first embodiment, the cooling rate can be increased by flowing a large amount of nitrogen gas through the pipe of the same size. further,
By jetting nitrogen gas from the upper and lower directions, the temperature difference generated during cooling between the upper and lower dies is reduced, so that the surface accuracy does not deteriorate.

In the present embodiment, the modification of the first embodiment can be applied as it is.

Note that, from a specific embodiment of the present invention,
The following technical ideas are derived. (Supplementary Note) (1) A mold set is provided with a pair of molds for holding the glass material and a sleeve slidably fitted to at least one of the molds, and the mold set is formed in an inert gas atmosphere. In a molding apparatus for an optical glass element that heats and softens the glass material by heating a mold set and press-molds, a holder that fits into the other mold of the mold set is provided, and the holder holds the glass material; and Along with fitting to the sleeve, disposed at a position surrounding the mold set,
A molding device for an optical glass element, comprising: cooling means for blowing an inert gas onto the mold set to cool the mold set.

According to the invention according to the supplementary note (1), with a molding device having a simple structure, the tact time is short, the production efficiency is high,
Optical glass elements can be molded. Further, by using the holder, it is possible to automatically assemble and disassemble the mold set, supply the glass material, and take out the formed optical glass element by using the transfer device.

[0031]

According to the first, second or third aspect of the present invention, an optical glass element can be molded with a short tact time and with high production efficiency by a molding apparatus having a simple structure.
According to the second aspect of the present invention, in addition to the above-described effects, by uniformly cooling the mold set from the direction of 360 degrees, the temperature distribution in the mold set is reduced, and an optical glass element with good surface accuracy is obtained. Can be. According to the third aspect of the present invention, in addition to the above-described effects, the heat sink is disposed at a position surrounding the mold set only when the mold set is cooled, and retreats out of the heating area of the heater when the mold set is heated. To prevent material deterioration of the blowpipe, and to prevent an increase in tact time by shielding infrared rays irradiated to the mold set.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an optical glass element forming apparatus according to a first embodiment.

FIG. 2 is a perspective view of a blow pipe according to the first embodiment.

FIG. 3 is an exploded configuration diagram of a mold set according to the first embodiment.

FIG. 4 is a perspective view of a blow pipe according to a second embodiment.

FIG. 5 is an enlarged sectional view of an outlet of an annular pipe according to a second embodiment.

FIG. 6 is a schematic configuration diagram of a conventional molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper mold 2 Lower mold 3 Sleeve 5 Glass material 9 Blow pipe 18 Model set

Claims (3)

[Claims] 1. A pair of molds for holding a glass material,
An optical element comprising a sleeve set slidably fitted to at least one of the shaping dies to form a mold set, and heating the mold set in an inert gas atmosphere to heat soften the glass material and press-mold. An apparatus for molding an optical glass element, comprising: a cooling device provided at a position surrounding the mold set to blow an inert gas onto the mold set to cool the glass set. 2. The optical glass element according to claim 1, wherein said cooling means is formed by an annular pipe, and a plurality of inert gas outlets are provided on an inner peripheral surface of the annular shape. Molding equipment. 3. The optical device according to claim 1, wherein the cooling unit includes a retracting unit that retracts out of a heating area of a heater that heats the mold set at least during molding of the optical glass element. Equipment for molding glass elements.