JPH0925128A - Lens forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a glass lens free from eccentricity by temporally fixing an optical glass blank between dies to assemble the dies, maintaining the base side of the first die under a negative pressure, temporally fixing this die to a vibration plate and pressing the optical glass blank by applying vibration thereon, thereby moving the optical glass blank toward the center of the die. SOLUTION: The optical glass blank 21 is held between the transfer surface 11a of the first die and the transfer surface 13a of the second die to form a die assembly prior to pressing at the time of forming the lens by pressing the optical glass blank 21 for forming between the first die 11 and the second die 13. The base side of the first die 11 is maintained under the negative pressure and this die is temporally fixed to the vibration plate 31. While the adequate pressing force is applied in this state on the optical glass blank 21 in the range where the optical glass blank 21 is made movable between the transfer surfaces by the vibration, the lens is formed by applying the vibration on the die assembly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding glass lenses by pressing.

[0002]

2. Description of the Related Art Conventionally, glass lenses have been manufactured through a polishing process for imparting a design curvature to a glass surface. However, in recent years, glass lenses having relatively small diameters such as aspherical lenses have been directly manufactured by press molding using a mold (Japanese Patent Publication No. 3-52417). In this pressing method, an optical glass material is sandwiched between a first mold and a second mold, and this is pressed under heating to duplicate the transfer surfaces of the first mold and the second mold. Then, the lens surface is obtained.

[0003]

SUMMARY OF THE INVENTION The present invention focuses on the fact that molding defects such as eccentricity often occur in the method of manufacturing a lens by the above pressing method, and one of the causes is the lower mold and the upper mold. We paid attention to the point that the optical glass material is pressed at a position deviated from the center of the transfer surface of the mold while being held. As a technique to solve this problem, an optical glass material is sandwiched between the lower die transfer surface and the upper die transfer surface to form a die assembly, and then the die assembly is placed on the diaphragm. Then, while applying an appropriate pressing force within the range in which the optical glass material can move between the transfer surfaces due to vibration, apply vibration to the mold assembly to move the optical glass material to the center of the transfer surface and then press-mold. (Japanese Patent Application No. 6-22
2492).

This pressing method is an effective method for preventing defective molding, but when vibration is applied by the vibrating plate, the entire mold assembly shakes greatly and the upper mold moves like bouncing, There was a concern that the mold assembly would move, fall, or drop from the diaphragm. In general, press molding of lenses is performed by continuous production, so that there is a certain process such as a mold assembling process.
Accidents in one process lead to not only the accident in that process but also the stoppage of the entire line, and the problem of industrial production is serious.

Therefore, the inventor of the present invention forms the entire diaphragm from a flexible material such as elastic rubber, or affixes a flexible material such as elastic rubber to the upper surface of the diaphragm, and uses a flexible member. I tried to absorb the shaking caused by vibration. However,
Although this method has achieved some success, it has become clear that there is still room for improvement. Therefore, the present invention applies vibration to the mold assembly to prevent eccentricity prior to pressing, and prevents the vibration from adversely affecting the mold assembly.
It is characterized in that the pretreatment (applying vibration) for press molding is stably performed.

[0006]

[Means for Solving the Problems] That is, the method of molding a lens according to the present invention is performed by pressing an optical glass material for molding between a first mold and a second mold to form a lens. Prior to the above, an optical glass material is sandwiched between the transfer surface of the first mold and the transfer surface of the second mold to form a mold assembly, and the bottom surface of the first mold is placed on the diaphragm. Along with
The first die is temporarily fixed to the diaphragm by making the bottom side of the first die a negative pressure, and the optical glass material is applied with an appropriate pressing force within a range in which the optical glass material can move between transfer surfaces by vibration. It is characterized in that the mold assembly is vibrated while being applied.

Regarding the uneven shape of the transfer surface, it is preferable that the transfer surface of at least one of the molds is a concave surface, and more preferably the transfer surfaces of both the first and second molds are a concave surface. By making the transfer surface concave, it is possible to move the optical glass material to the center of the mold by vibration and prevent the occurrence of eccentricity, and press-mold the lens.

[0008]

1 to 3 are explanatory views showing an embodiment of a lens molding method of the present invention. In this embodiment of the present invention, the optical glass material 21 is placed on the transfer surface 11a of the lower mold 11 (first mold) with the transfer surface 11a which is the replication surface facing upward, and Positioning is performed by the set guide mold body 15, the upper mold 13 is fitted to the guide mold body 15 and the mold is assembled to form a mold assembly. Conventionally, press molding was performed in this state.

In the present invention, as shown in FIG.
Then, the upper mold 13 is assembled into a mold, and the optical glass material 21 is placed on the vibration table 31 (vibration plate) in a state where the optical glass material 21 is temporarily restrained by its own weight and temporarily regulated. Lower mold 11
A plurality of suction holes 33 (through holes) are provided on the vibration table 31 covered with the bottom surface of the suction table 33, and all of the plurality of suction holes 33 communicate (open) with a suction chamber 35 that forms a closed space. ing. Into the suction chamber 35, the suction pipe 3 for sucking and exhausting the air in the suction chamber 35 to a negative pressure or introducing the air into the suction chamber 35 which has become a negative pressure and returning to the normal pressure.
7 is provided. The suction pipe 37 communicates with a pump pipe 41 and a leak pipe 45 via a solenoid valve 39.

Prior to applying vibration to the mold assembly, FIG.
In the state where the mold assembly is placed on the vibration table 31 as shown in FIG. 3, the valve 39a of the electromagnetic valve 39 is opened and the valve 39b is closed, and the suction pump 43 (or the vacuum exhaust pump) is used to move the inside of the suction chamber 35. When the air is exhausted through the suction pipe 37, the solenoid valve 39, and the pump pipe 41, the inside of the suction chamber 35 becomes negative pressure, and the suction hole 33 causes the bottom side of the lower mold 11 of the mold assembly to become negative pressure, and the lower mold 11 passes through. Vibrating table 31
Temporarily fixed to. With this mold assembly temporarily fixed to the vibration table 31, the diaphragm 51 having a bellows structure is expanded and contracted by a voice coil (not shown) in the direction of the arrow A, and the optical glass material 31 is appropriately adjusted by the weight of the upper mold 13. Vibration is applied to the entire mold assembly to which the pressing force of is applied.
Here, the appropriate pressing force means that when the optical lens material 21 is sandwiched at a position deviated from the center between the transfer surfaces 11a and 13a, the optical lens material 21 is vibrated to cause the optical lens material 21 to move.
The pressing force is such that it can move to the center of a, 13a.

If the optical glass material 21 is displaced from the center of the transfer surfaces 11a and 13a due to the impact due to this vibration, the optical glass material 21 moves to the center of the transfer surfaces 11a and 13a and the transfer surfaces 11a and 13a. It moves to the center of the table and then stops moving (see Figure 2).

Next, when the vibration of the vibration table 31 by the diaphragm 51 is stopped, the solenoid valve 39 is switched, the valve 39a is closed and the valve 39b is opened, the leak pipe 47, the leak pipe 45, the solenoid valve 39, and the suction pipe. Air in the atmosphere flows into the suction chamber 35 via 37, the suction chamber 35 becomes atmospheric pressure, and the suction / temporary fixing of the bottom surface of the lower mold 11 due to the negative pressure is released. As a result, the die assembly that can be freely transferred is sent to the next step, and after heating, in the pressing step, the pressing block 61 is pressed down by a pressing cylinder (not shown) as shown in FIG. By heat-pressing with the mold 13 and the lower mold 11, the transfer surfaces 11a, 13a are transferred and duplicated to mold the optical glass material 21, and a glass lens 21 'having no eccentricity is obtained.

Now, assuming that the optical glass material 21 is pressed in a state where it is not at the center position of the transfer surfaces 11a and 13a as shown in FIG. 1, at the time of lens molding (at the time of pressing).
Since the optical glass material 21 is evenly molded from the contact point with the mold, the optical glass material 21 is molded to the full extent of the guide mold body 15 in one direction, but to the guide mold body 15 in the other direction. The optical glass material 21 is not molded, and the resulting glass lens 21 'is decentered. On the other hand, in the present invention, the optical glass material 21 ensures that the transfer surface 11
Since it is installed at the center of a and 13a, a glass lens 21 'having no decentration can be obtained.

In the molding method of the present invention, the transfer surface of at least one of the upper mold and the lower mold is concave.
That is, it is suitable for molding a lens having at least one convex surface, for example, for molding a meniscal lens or a plano-convex lens, which ensures that the optical glass material is positioned at an appropriate center position on the transfer surface during vibration before pressing. Can be moved to. More preferably, the biconvex lens is formed by using an upper die and a lower die whose transfer surfaces are both concave. In this case, the optical glass material is moved to a proper position on the transfer surface more surely and pressed. The lens can be molded, and the lens can be molded while preventing eccentricity. The molding method of the present invention can also be used for molding plano-concave lenses and biconcave lenses.

The temporary fixing method by negative pressure according to the present invention is not limited to the above-mentioned embodiment, and various modifications can be utilized. For example, the following specific examples can be given. (1) Vibration table 31 as a whole, or vibration table 3
The surface of the vibrating table 31 in which 1 is brought into contact with the bottom surface of the lower die 11 is formed of an elastic or flexible member such as rubber or soft plastic to enhance the adhesion between the vibrating table 31 and the lower die 11 to form a vacuum. Improves sealing properties. (2) The suction chamber 35 is not always necessary, and the suction port 33 may be directly connected to the suction pipe 37. (3) The number of suction ports 33 may be one, or a number of smaller suction ports 33 may be densely provided. Further, although FIG. 1 shows a case where vibration is applied to the mold assembly in the vertical direction, the vibration direction is not limited and may be any direction such as the horizontal direction.

[0016]

According to the present invention, after the optical glass material is attached to the mold to form the assembly, the optical glass material is vibrated while the pressing force is applied to the optical glass material to transfer the optical glass material. By locating the lens at the center of the surface and press-molding it, an optical lens in which eccentricity is prevented can be easily manufactured by a pressing method. Furthermore, since the mold assembly is temporarily fixed to the vibrating body using negative pressure to give vibration,
As the mold assembly swings on the diaphragm and falls or moves, it prevents eccentricity from occurring immediately without affecting the transfer to the next process or the process in the next process. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view showing a method for molding a lens of the present invention.

FIG. 2 is an explanatory cross-sectional view showing a lens molding method of the present invention.

FIG. 3 is an explanatory cross-sectional view showing a lens molding method of the present invention.

[Explanation of symbols]

 11 Lower Mold 11a Transfer Surface 13 Upper Mold 13a Transfer Surface 15 Guide Mold 21 Optical Glass Material 21 'Glass Lens 31 Vibration Table 35 Suction Chamber 37 Suction Pipe 39 Solenoid Valve 39a, 39b Valve 41 Pump Piping 43 Suction Pump (Vacuum Pump) ) 45 Leak piping 47 Leak hole 51 Diaphragm 61 Pressure block

Claims (2)

[Claims] 1. When a lens is molded by pressing an optical glass material for molding between a first mold and a second mold, prior to pressing, a transfer surface of the first mold and a second mold are formed. An optical glass material is sandwiched between the mold transfer surface to form a mold assembly, the bottom surface of the first mold is placed on the diaphragm, and the bottom surface side of the first mold is negative pressure. As a result, the first mold is temporarily fixed to the vibration plate, and the optical glass material is given a suitable pressing force within a range in which the optical glass material can move between the transfer surfaces due to the vibration, and the vibration is applied to the mold assembly. Characteristic lens molding method. 2. The lens molding method according to claim 1, wherein the transfer surface of at least one of the molds is a concave surface.