JPS6011317A - Releasing apparatus of mold for plastic lens - Google Patents

Abstract

PURPOSE:To improve the surface accuracy of a lens, by providing, as a releasing mechanism in a mold for molding a plastic lens, a combination of a mechanism for pushing up a molded lens surface and a mechanism for pushing up the edge portion of a lens surface, and allowing the mechanisms to be operated separately. CONSTITUTION:After a lens 1 is molded, it is cooled, the mold is opened, and the lens is released from a releasing plate 7 via a piece block 4 and a lens core 2. Then through a connecting plate 8 the releasing plate 7 is slid upward, and the molded lens 1 is released from the lens core 2. Successively, through the connecting plate 8, the releasing plate 7 is slid downward to return the releasing plate to the original state. The molded lens 1 has been already released from the lens core 2, and it only rests on the upper surface of the lens core 2. Thus, the deterioration of the accuracy of the configuration of the lens surface and the deformation of the edge portion of the lens can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a mold for forming a plastic lens, and particularly to a lens ejection mechanism intended to improve lens surface precision.

[Background of the invention]

Typical methods for manufacturing plastic lenses include injection molding and heat compression molding. In both cases, thermoplastic resin is heated and melted above the plasticizing temperature of the resin.
This is a method of filling and molding into a mold under high pressure. Therefore, the molds used in these processing methods are basically composed of common parts and have almost the same functions.

In particular, the method for removing a molded lens from a molding die is exactly the same, and has conventionally been released and taken out from a mold using the structure shown in FIG. That is, the molded lens 1 that is in close contact with the lens insert piece 2 that forms the lens surface shape is pushed up from the movable frame body 6 by the ejector rod 6 of the molding machine via the connecting piece 4 and the ejector plate 5, and then the molded lens 1 was released from the lens insert 2 by hand or by a take-out machine and taken out.

However, even when the molded lens 1 is pushed up from the movable frame, the surfaces of the molded lens 1 and the lens insertion piece 2 are in strong contact with each other, so a very large mold release force is applied to take out the molded lens. do.

For this reason, depending on the contact state between a molded lens removal jig such as a removal machine and the edge of the lens surface, an imbalance of mold release force may occur, causing deterioration of the lens surface. Furthermore, depending on the temperature at which the molded lens 1 was taken out, there were defects such as deformation of the edge portion or peeling of the lens surface.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to provide a plastic that can prevent deterioration of the shape accuracy of the lens surface and deformation of the lens edge by releasing the lens in a well-balanced manner using injection molding or heat compression molding. An object of the present invention is to provide a mold release device for a lens mold.

[Summary of the invention]

For this purpose, the mold release device for the plastic lens mold of the present invention is equipped with a mold release plate driven by a hydraulic cylinder to evenly release the molded lens surface and the lens surface insertion piece. It is said that

Furthermore, a control mechanism is provided that measures the temperature of the molded lens and prevents deterioration of the precision of the molded lens or deformation of the edge portion due to the mold release force acting on the molded lens.

[Embodiments of the invention]

The present inventors variously changed the lens shape, lens material, molding conditions, etc., and studied the influence of mold release force on lens surface accuracy. As a result, the mold release force that acts on the lens surface during mold release is almost unaffected by the lens shape, and is dominated by the contact area between the lens surface and the lens insert, the lens material, and the lens temperature during mold release. Understood.

In other words, the unit release force acting on the lens surface is the lens release temperature ratio: N (N=TL
/T? ), as shown in FIG. 2, there is a tendency for the ratio to increase as the lens release temperature ratio -N increases. In particular, it was found that even in plastic materials with b deviation, when the lens mold release temperature ratio: N exceeds 08, the mold release force increases rapidly. When the temperature dependence of the tensile strength of the lens material, which is directly related to the deformation of the 1fc lens surface, is organized by the lens template temperature ratio: N, as shown in Figure 3, the temperature dependence of the tensile strength of the lens material, which is directly related to the deformation of the lens surface, is It was found that there was a tendency for the value to decrease as a result.

゛ Based on these findings, the deterioration of the lens surface, that is, W
Examining the relationship between the deviation from the AD value and the temperature at the time of lens release, and organizing it according to the lens release temperature ratio (N) as described above, we can see that as the lens release temperature ratio increases, the lens temperature decreases as shown in Figure 4. It became clear that the surface deviation tended to increase.

In particular, when the lens mold release temperature ratio: N exceeds 0.8, a more remarkable deviation in the mold release force is observed.

In other words, considering mass production, it is desirable to release from the mold at the highest possible temperature during the molding cycle. On the other hand, considering mass production such as the required specification 2 yield for the lens, it is necessary to minimize the deviation of the lens surface. Based on the required characteristics of both of these and the temperature dependence of lens surface accuracy obtained in Figure 4, the temperature at the time of lens release can be obtained from the glass transition temperature of the lens material and the lens release temperature ratio: N=08. It was understood that the value given below is optimal.

The present inventors have focused on this phenomenon and have devised a mold release device for a plastic lens mold that can monitor the lens temperature during mold release and evenly release the lens surface.

The mold release device of the present invention will be described in detail below with reference to the drawings. FIG. 5 is a block diagram showing an embodiment of a device for implementing a releasing device for a plastic lens mold of the present invention.

In this figure, elements 1 to 6 are the same as those described in the prior art shown in FIG. 1.

Reference numeral 7 denotes a release plate, which is connected to the release cylinder 9 via a connecting plate 8, and is operated by hydraulic oil supplied to the release cylinder 9 from a hydraulic oil pressure source 10 via an electromagnetic directional valve 11. Slides vertically. In addition, the release plate 7
is held by four guide bins (not shown) via guide bushes, and has a structure that allows it to slide smoothly with respect to the central axis of the lens insertion piece 2 without tilting. Reference numeral 12 denotes an infrared thermometer for measuring the temperature of the molded lens, and the measured value is transmitted to the controller 14 via the amplifier 13. 15 is an air outlet, and a clean air unit 16. Solenoid directional valve 17
It has a function of injecting the compressed air obtained from the air source 18 to the molded lens 1 via the air source 18 to rapidly cool the molded lens 1.

The operation of the cooling device configured as described above will be explained using an example of a concave meniscus lens molded from acrylic resin.

The molded lens is composed of a spherical surface with a radius of curvature of 220 mm + 125 m +, and its center thickness is Aw.

The outer diameter of the lens is 135 mm. The molded lens is produced by heating the surface of a lens blank, which has been processed into a roughly lens shape by injection molding, at 150° C. for 40 molecules, and then inserting it into a molding die, and shaping the lens surface by pressurizing and compressing it. . Approximately 1
After cooling for 5 minutes, the mold is opened and the ejector rod 6 of the molding machine
, the release plate is released from the mold via the ejector plate 51 connecting piece 4 and the lens inserting piece 2, resulting in the state shown in FIG. At this point the controller 14 has activated the infrared thermometer 12. The temperature of the lens 1 is measured via the amplification amplifier 16. If the measured lens temperature is below the glass transition point of the acrylic resin, which is 105°C, and the appropriate mold release temperature obtained from the lens mold release temperature ratio: N = 0.8: To = 8A°C,
The hydraulic pressure source 10 immediately passes through the electromagnetic directional valve 11.
Hydraulic oil is supplied to the mold release cylinder 9, and the mold release plate 7 is slid upward via the connection plate 8 to release the molded lens 1 from the lens insert piece 2 as shown in FIG.

On the other hand, when the temperature of the molded lens 1 is equal to or higher than the appropriate mold release temperature of 84°C, the electromagnetic switching valve 17. clean air uni,
G16. Compressed air obtained from an air source 18 is blown onto the surface of the molded lens 1 via the air outlet 15 to cool the molded lens 1. The controller 14 is an infrared ff
M thermometer 12. The temperature of the molded lens 1 is monitored by the temperature measurement unit of the amplifier 13, and when this temperature has cooled down to the appropriate mold release temperature of 84° C., molding is performed using the same sequence as described above as shown in FIG. The lens 1 is released from the lens inserting piece 2 by a mold release source. In this state, the molded lens 1
is buried inside the mold release plate 7, and it is difficult to take it out from the mold using a take-out machine or the like. Therefore, by switching the mode of the electromagnetic directional control valve 11, the release cylinder 9
゜Slide the mold release plate 7 downward via the connection plate 8 to return the mold release plate to its initial state as shown in FIG. The molded lens 1 has already been released from the lens insert piece 2, and is merely resting on the upper surface of the lens insert piece 2, as shown in FIG.

As a result, the molded lens 1 can be easily released from the mold using a take-out machine or by hand.

〔Effect of the invention〕

As explained above, according to the present invention, a molded lens can be taken out from a molding die under appropriate mold release conditions that take into account both mass productivity and lens surface precision. Furthermore, since the edge of the lens surface can be evenly pushed up by the release plate, it is possible to prevent deterioration of lens surface precision or deformation of the edge of the lens surface due to imbalance in the release force, which was a drawback of conventional technology. It has become possible. As a result, the amount of deformation of the lens surface that occurred during mold release could be reduced to 115 compared to the conventional value. In addition, the molding cycle is 8
We obtained the effect of being able to shorten the time to 0%.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing a conventional mold release device, Figure 2 is a characteristic diagram showing the relationship between molded lens temperature and mold release force, and Figure 3 is a characteristic diagram showing the temperature dependence of lens material strength. Figure 4 is a characteristic diagram showing the relationship between molded lens temperature and lens surface accuracy.
FIG. 5 is a block diagram showing an embodiment of a mold release device for a plastic lens mold of the present invention, and FIGS. 6 and 7 are explanatory diagrams of a mold release process for a molded lens, respectively. 1... Molded lens, 2... Lens surface insertion piece, 7...
・Release plate, 9...Release cylinder, 12...
Infrared thermometer, 14...controller, 15...air outlet. Kaya 7 figure

Claims (1)

[Scope of Claims] 1. In a mold for manufacturing plastic lenses by injection molding and heating compression molding, there is provided a mechanism for pushing up the molded lens surface and releasing the lens edge portion from the mold, and a drive. It is equipped with a mechanism for releasing the molded lens surface and the lens surface inserting piece by pushing up the lens surface edge portion driven by a means, and that each mold release mechanism is movable individually. Characteristic mold release device for plastic lens molds. 2. The mold release device according to claim 1 is equipped with a device capable of measuring the temperature of the molded lens at the time of mold release, and the lens temperature at the time of mold release: TL is the glass transition temperature of the molded lens material: Lens release temperature ratio divided by Tt: N is 0.
A mold release device characterized in that the molded lens is released from the lens surface inserting piece when the value becomes 8 or less. 3. The mold release device according to claim 1 or 2 is equipped with a device capable of cooling the molded lens by injecting compressed air passed through a clean air unit onto the molded lens surface. A mold release device, characterized in that the molded lens and the lens surface inserting piece are released from the mold after the molded lens is cooled until the temperature of the skeleton molded lens becomes equal to or less than the lens mold release temperature ratio 2N of 0.8.