JPH04144929A - Production of glass lens and producing device therefor - Google Patents

Abstract

PURPOSE:To prevent occurrence of fog of glass lens by retaining a glass raw material so that the surface may be kept in non-contact state, heating the glass raw material alternately to a temperature lower than the glass transition temperature and a temperature higher than the softening point of the glass of the glass to keep the glass raw material in a specific state and then subjecting the glass raw material to press molding to form glass lens. CONSTITUTION:A glass raw material 1 is performed into a shape close to lens and retained above a carrying member 8 so that the surface may be kept in on-contact state and set on a changing table 3 and carried in to a contains heating furnace 4 at definite intervals. Heating at a temperature not higher than the glass transition temperature by low-temperature furnaces 41-44 of glass raw material 1 and heating at a temperature not lower than softening point by high-temperature furnaces 45-48 are alternately repeated and the center part of glass raw material 1 is retained to a temperature not higher than the softening point and the surface part is retained to a temperature not lower than the softening point to control deformation by heating. Thereby the surface part is made smooth. Then the glass raw material is transferred into a forming mold 5 and molded into glass lends 1a having prescribed form by upper mold 52 and lower mold 53 and the resultant lens is released from molds and gradually cooled in a gradually cooling part 6 and carried onto a discharge table 7 and cooled to ambient temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can be applied to a method of manufacturing a glass lens in which a glass material preformed into a lens shape is heated and then press-molded, and a method of manufacturing the same. Regarding manufacturing equipment.

[Prior art] This type of technology has been disclosed in Japanese Patent Application Laid-Open No. 63-277528.
The technique disclosed in the above publication is known. FIG. 5 shows the concept of the above technology, in which a pair of upper and lower heating blocks 10
1, 102 and molds 103, 104 are arranged adjacently. The heating blocks 101 and 102 are temperature-controlled to a predetermined temperature, and the glass material 1
The glass material 100 is heated by heat transfer by contacting the glass material 100 from above and below. At the same time as this heating, the heating block 101.
102 presses the glass material 100 to preform it.

The glass material 1oo heated by the heating blocks 101 and 102 is then placed in the heated molds 103 and 104.
The glass lens 100a is formed into a predetermined shape by being transferred between them and pressed. In the prior art, such a method improves the heating efficiency of the glass material, making it possible to shorten the manufacturing time of glass lenses and improve reversibility during molding.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, since the glass material is heated by thermal conduction when the heating block comes into contact with it, cloudiness occurs on the surface of the glass material that comes into contact with the heating block. This is because volatile components generated from the glass material due to heating adhere to the surface, and this is particularly noticeable in glasses containing a large amount of lead components, such as SF glass. For this reason, the conventional technology has had the problem that the glass materials that can be molded are limited.

The present invention has been made in view of the problems of the prior art described above, and does not cause clouding and can be applied to a wide range of glass materials.Moreover, it shortens manufacturing time and does not impair reversibility during molding. An object of the present invention is to provide a method for manufacturing a glass lens and an apparatus for manufacturing the same.

[Means for Solving the Problems] In order to achieve the above object, the method for manufacturing a glass lens of the present invention involves holding a glass material so that the surfaces are in a non-contact state, and in this holding state, the glass transition point of the glass material is increased. The glass material is heated so that the surface area becomes hotter than the center area by passing it alternately through the following heating areas and heating areas above the softening point, and then press-molded into a predetermined lens shape using a mold. This is a distinctive method for manufacturing glass lenses.

Further, the glass lens manufacturing apparatus of the present invention that can be applied to this manufacturing method includes a low temperature furnace that heats the glass material to a temperature below the glass transition point and a temperature furnace that heats the glass material to a temperature above the softening point. A plurality of continuous heating furnaces arranged alternately in communication, a mold for press-molding the glass material heated by the continuous heating furnace, and a conveying means for holding and transporting the glass material without contacting the surface of the glass material. This is a glass lens manufacturing apparatus characterized by comprising:

[Function] In the manufacturing method having the above configuration, the central portion of the glass material is heated to a temperature below the softening point by passing the glass material alternately through a heating region below the glass transition point and a heating region below the softening point. On the one hand, deformation during heating is suppressed, and on the other hand, the surface portion of the glass material has a softening point temperature or higher, which is higher than that of the central portion, so it becomes smooth and has good moldability. Moreover, since the glass material is held and passed through these heating areas without contacting the surface, volatile components do not adhere to the surface and no warping occurs.

In addition, in the manufacturing apparatus with the above configuration, the glass material can be heated in a manner suitable for the above conditions using a continuous heating furnace in which a plurality of low-temperature furnaces and high-temperature furnaces are arranged alternately. It is possible to carry out transportation within the heating furnace in a state where no generation occurs.

[Example] Hereinafter, the present invention will be specifically explained by referring to an illustrative example.

FIG. 1 shows an embodiment of a manufacturing apparatus for carrying out the manufacturing method of the present invention, and FIGS. 2 and 3 show cross-sectional views taken along the line 1--2 and the line 2--2. This manufacturing device molds a glass lens 1a while conveying a glass material 1. As shown in FIG.
．． Continuous heating furnace 4. Molding mold 5. An annealing section 6 and a discharge table 7 are arranged in this order. The charging table 3 is used to arrange the glass materials 1 and sequentially feed them into the continuous heating furnace 4. In this case, the glass material 1 is held by the conveying member 8 and used for molding the glass lens, and the conveying member 8 holds the glass material 1 as shown in FIG.
It has a ring shape with an open top and bottom that individually supports the glass material 1 by abutting only the outer peripheral portion of the glass material 1. By placing the glass material 1 in this conveying member 8,
The upper and lower surfaces are transported together with the transport member 8 in a non-contact state.

The continuous heating furnace 4 is configured such that low temperature furnaces 41, 42, 43, 44 and high temperature furnaces 45, 46, 47, 48 are arranged alternately. That is, a low temperature furnace 41 is connected to the charging table 3, a high temperature furnace 45 is connected to this low temperature furnace 41, and the low temperature furnaces 42, . High temperature furnace 46. Low temperature furnace 43. High temperature furnace 47, low temperature furnace 44. A high temperature furnace 48 is connected. In this case, the low-temperature furnaces 41 to 44 are arranged in a straight line, but the last high-temperature furnace 48 is arranged in a direction orthogonal thereto, thereby reducing the space required for arrangement. Such a continuous heating furnace 4 heats the glass material 1 held by the conveying member 8 as it passes therethrough, and adjacent furnaces are interconnected internally as shown in FIG. At the same time, a conveying path 9 for moving the conveying member 8 is installed in a penetrating state. The low-temperature furnaces 41, 42, 43.44 heat the glass material 1 to the glass transition (Tg) temperature, while the high-temperature furnaces 45, 46, 47.48 heat the glass material 1 to its softening (S) temperature.
These low temperature furnaces 41,
42, 43.44 and high temperature furnace 45, 46, 47.48
has a built-in heater that heats the glass material 1 to a target temperature.

By alternately arranging the low temperature furnaces 41, 42, 43, 44 and the high temperature furnaces 45, 46, 47, 48 in this way,
As will be described later, heating can be performed such that the surface portion of the glass material 1 is at a higher temperature than the center portion. Further, since the continuous heating furnace 4 continuously heats the glass material 1 while conveying it, the time required for heating can be shortened, and the manufacturing time can be shortened. The mold 5 press-forms the glass material 1 heated by the continuous heating furnace 4 into a glass lens 1a having a predetermined lens surface, and is connected to the last high temperature furnace 48.

As shown in FIG. 3, this mold 5 includes an upper mold 52 disposed oppositely within a housing 51 erected on the base 2.
and a lower mold 53, and a molding surface for molding a predetermined lens surface is formed on opposing surfaces of the upper mold 52 and the lower mold 53. In this case, the upper mold 52 is fixed to the lower surface of an upper plate 54 mounted on the housing 51. On the other hand, the lower mold 53 is attached to the upper end of a press shaft 55 that passes through the base 2 and moves up and down. This press shaft 55 is supported by an air cylinder 56 attached to the bottom surface of the base 2, and is moved up and down by the operation of the cylinder 56. Therefore, in the illustrated example, the lower mold 5
3 moves upward and comes into contact with the upper die 52, these press the glass material 1, thereby forming the glass lens 1a.
It has a structure that molds. Note that the upper mold 52 and the lower mold 53 have built-in heaters (not shown) to maintain a predetermined temperature.

57 is a bearing for smoothly moving the press shaft 55 up and down. Such a mold 5 is used in the temperature furnace 48 of the continuous heating furnace 4.
The glass material 1 is transferred together with the conveying member 8 from the upper mold 5.
2. Press molding is performed by being inserted between the lower molds 53, and in order to perform this transfer, the input hand 1
o is provided on the base 2 (see FIG. 1). The charging hand 10 includes a hand 11 that holds the conveyance member 8, and this hand 11 is connected to the charging port 4 of the last high temperature furnace 48.
9 (see FIG. 2), and by further advancing, the conveying member 8 holding the glass material 1 is transferred to the pressing position of the mold 5.

The annealing section 6 is for annealing the glass lens la press-molded by the mold 5, and an annealing furnace 61 for this purpose is connected to the mold 5. The slow cooling furnace 61 is a continuous heating furnace 4
It is possible to use a low-temperature furnace having a structure similar to that of the low-temperature furnace shown in FIG. Further, a discharge hand 12 is provided to transport the glass lens 1a from the mold 5 into the lehr 61 together with the transport member 8 (see FIG. 1). This ejection hand 12 can have the same configuration as the input hand 1°, and when the hand 13 passes through the lehr 61 and advances to the press position of the mold 5, it becomes a conveying member holding the glass lens la. 8 is held in the lehr-cooling furnace 61.
to be transferred within. Then, the conveying members 8 transferred into the slow cooling furnace 61 are discharged to the discharge table 7 through the discharge port 63 through the discharge path 62, and are aligned on the discharge table 7.

Next, a specific example of a manufacturing method using the manufacturing apparatus having the above configuration will be described.

First, the glass material 1 is preformed to have a shape similar to the shape of the lens to be molded, and the glass material 1 is placed on each of the conveying members 8 and set on the input table 3. After the conveying members 8 are aligned by a robot hand or the like on the charging table 3, the conveying members 8 are carried into the continuous heating furnace 4 at regular intervals by a supply means such as a cylinder (not shown). In the continuous heating furnace 4, the conveying member 8 is conveyed at a constant pitch from the low temperature furnace 41 to the high temperature furnace 48, and is heated by the low temperature furnaces 41, 42, 43, 44 and the high temperature furnace 45,
46, 47, and 48 are repeated alternately.

Then, in the low temperature furnaces 41, 42, 43, 44, the glass material "1 is heated to a temperature below the glass transition (Tg1 point), and in the high temperature furnaces 45, 46, 47, 48 it is softened (
The glass material 1 is heated to a temperature of Sp1 point. By repeating such heating, a temperature difference occurs between the surface portion and the center portion of the glass material 1, and the temperature of the center portion becomes equal to or lower than the softening point, so that deformation of the glass material 1 due to heating can be suppressed. On the other hand, the surface portion of the glass material 1 has a temperature higher than the softening point, which is higher than the center portion. In such a high temperature state, the surface portion of the glass material 1 becomes smooth and the surface roughness is reduced, resulting in good moldability. That is, by keeping the center part of the glass material 1 at a temperature below the softening point and bringing the surface part to a temperature above the softening point, the surface part is made smooth while suppressing thermal deformation. , As a result, a glass lens can be well formed even from the glass material 1 having a maximum surface roughness value Rmax of 1 μm or more,
Even if the preform accuracy is poor, a desired glass lens can be obtained.

FIG. 4 shows the thermal history when SF8 having a Tg point of 443°C and an Sp point of 567°C is used as a glass material.

This glass material is preformed into a biconvex lens shape with an outer diameter of 10 mm, wall thickness of 2 mm, radius of curvature of 11 mm, and 30 mm, and its surface is polished with a metal grindstone to a surface roughness of Rmax = 2 μm. It was then transported into the continuous heating furnace 4. In this case, the low temperature furnaces 41, 42, 43, 44 are set at 450°C, and the high temperature furnaces 45, 4
6.47.48 was controlled at a temperature of 800℃, and the inside of the low-temperature furnace was heated at 800℃ at a conveying speed of 20 seconds.
The lengths of these furnaces were set so that it would pass through the high temperature furnace in 40 seconds. The signs of the parts separated by chain lines in the figure correspond to the respective low temperature furnaces 41, 42, 43.44 and high temperature furnaces 45, 46, 47.48, and the solid line A indicates the temperature of the surface part of the glass material. , broken line B indicates the temperature at the center. As shown in the figure, while the temperature of the center part is kept below the softening point, the surface part is heated above the softening point, and even if the surface roughness is 1 μm or more, the surface part can be made smooth. can. The heating conditions, conveyance pitch, length of the furnace, etc. are appropriately selected depending on the material and size of the glass material.

During heating in the continuous heating furnace 4 as described above, only the outer peripheral portion of the glass material 1 is in contact with the conveying member 8, and the surface portion is in a non-contact state. Components do not dissipate and adhere to the surface. For this reason, the surface of the glass material (does not get sticky),
Since a good glass lens can be obtained even with an SF glass material, a wide variety of glass materials can be used.

By passing through the continuous heating furnace 4 in this manner, the surface portion of the glass material 1 is heated and softened to become smooth, and the surface roughness at the exit portion becomes as small as Rmax=0.07 mm. Therefore, the surface roughness suitable for press molding is transferred into the mold 5, and the upper mold 52 and the lower mold 5
3, the glass lens is molded into a desired shape. After this press molding, the mold is released and transferred to the slow cooling section 6 where slow cooling is performed. In the case of the above-mentioned glass material, this slow cooling can be performed by setting the slow cooling furnace 61 to 200°C.
After this slow cooling, it is carried out to the discharge table 7 and
It is then cooled to room temperature to complete the molding.

Note that the present invention is not limited to the above embodiments,
Various changes are possible, for example, the number of continuous heating furnaces, temperature conditions, etc. can be changed depending on the material and form of the glass material, and the mold may also be of an upper type press or a double type press.

[Effects of the Invention] As explained above, according to the present invention, since the surface of the glass material is heated in a non-contact manner, volatile components do not adhere to it and clouding does not occur. Therefore, it can be applied to a wide range of glass materials.

In addition, by repeating the process of heating the glass material to a temperature below the glass point transition and the process of heating it above the softening point, in order to smooth the surface part while suppressing thermal deformation of the central part of the glass material, Even glass materials with large surface roughness can be press-molded successfully. moreover,
Since the glass material is heated while being transported, manufacturing time can be shortened.

[Brief explanation of drawings]

FIG. 1 is an overall plan view showing an embodiment of a manufacturing apparatus applied to the manufacturing method of the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■, FIG. 3 is a cross-sectional view taken along the line ■-■, FIG. 4 is a characteristic diagram showing the thermal history during heating of a glass material, and FIG. 5 is a side view showing the concept of the prior art. l... Glass material 1a... Glass lens 4... Continuous heating furnace 5... Molding mold 8... Conveying member 41.42, 43.44 -... Low temperature furnace 45.46, 47.48 ...High temperature furnace 52...Upper mold 53...Lower mold diagram Fermentation diagram

Claims (2)

[Claims] (1) Hold the glass material so that the surfaces are in a non-contact state, and in this held state, pass the glass material alternately through a heated region below the glass transition point and a heated region above the softening point, so that the surface is closer to the center than the center. A method for manufacturing a glass lens, which comprises heating a glass material so that a portion thereof reaches a high temperature, and then press-molding it into a predetermined lens shape using a mold. (2) a continuous heating furnace in which a plurality of low-temperature furnaces that heat the glass material to a temperature below the glass transition point and a plurality of temperature furnaces that heat the glass material to a temperature above the softening point are alternately arranged in a communicating state;
A glass lens comprising a mold for press-molding a glass material heated in a continuous heating furnace, and a conveying means for holding and conveying the glass material without contacting the surface of the glass material. Manufacturing equipment.