JPH02208012A - Mold for forming plastic lens - Google Patents

Abstract

PURPOSE:To relieve the impart to a pushing pin by mold clamping while high accuracy of brim surface and miniaturizing and lightening thereof may be obtained by pushing out the whole periphery of the brim surface of a lens by a ringlike plate through the pushing pin. CONSTITUTION:After the resin packed in a cavity 1 has been solidified, if a stationary mold is separated from a movable mold left and right by the mold- opening operation of a molding machine from parting face 28, the stationary mold is released, and a lens 1a is stuck to the cavity of the movable mold and is kept these. A pushing pin 4 and a ring plate 23 are advanced by the retreating of the movable mold accompanied with mold opening, whereby the lens 1a may be suitably taken out from the ring plate by a robod on the hand of an operator. Since the construction pushing out the whole periphery of the lens brim by the ring plate through the pushing pin is used, there is no occurrence of burrs or unevenness on the brim surface of the lens. The smoothness of the brim surface depends on the flatness of the ring plate, and such flatness may be obtained, by working so as to satisfy its design specification.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to molds for plastic lenses used for various photographic lenses such as cameras, lenses used for reproduction and recording of laser discs, etc., and projection tubes such as projection televisions. Regarding.

[Conventional technology]

Release of plastic lenses from molds is described in Japanese Patent Application Laid-Open No. 1983-
As described in Japanese Patent No. 27500, a method of extruding and releasing the optical surface of a plastic lens is generally widely used. In addition, for plastic lenses where the lens diameter is large and the weight of the lens is not so important, please refer to the literature (Panel Technology: Vol. 3, No. 13b, October 1988 issue).
As described in , a method is used in which a so-called flange surface formed around an optical surface is extruded with an extrusion pin and released from the mold.

[Problem to be solved by the invention]

In the above conventional technology, for example, the method of extruding the lens optical surface and releasing it from the mold does not take into account galling of the sliding surface (the outer periphery of the insert piece that forms the lens surface), which is the most important input part of the metal component. There was a problem with damaging the pieces. For this reason, a method of extruding the flange surface 2 of the lens as shown in FIG. 6 has come to be used, but no consideration has been given to the accuracy of the flange surface or to miniaturization and weight reduction of the lens. This will be explained in more detail using FIGS. 7 and 8. In FIG. 6, the tip 4a of the ejector pin tends to have irregular heights.If the tip 4G is configured to protrude into the cavity, it will bite into the molded product, making it difficult to release the molded product from the ejector pin 4. Have difficulty. Therefore, for boat fishing, the tip is configured so as not to protrude into the cavity 13b1t. Therefore, as shown in FIG. 7, a projection (boss) is formed at the push-out pin position. Since the lengths t of the bosses are uneven as described above, a method is used to avoid holding the lens barrel with the bosses when assembling the lens barrel. Similarly, a method is also taken to avoid the influence of flakes occurring on the sliding portion of the ejector pin. A common method for this is to assemble it on the outside of the boss or the boss via a spacer, as shown in FIG. However, since such a method increases the outer diameter of the lens, the diameter of the lens barrel inevitably tends to increase as well, which poses problems in making the product compact and lightweight.

In addition, in the method using the extrusion pin, it is necessary to secure an extrusion area for mold release, and the size of the flange surface must be increased.In order to solve this problem, as shown in FIG. A method of cutting out the extrusion pin and using it has also been proposed, but the roundness of the outer shape of the collar deteriorates, which limits its application to high-precision products.

As mentioned above, conventional molds for plastic lenses have problems with the life of the insert pieces, the accuracy of the lens rim surface, and the reduction in size and weight of the lens closure.

An object of the present invention is to provide a mold that enables high precision of the flange surface and is small and lightweight. Further, the above-mentioned mold has a structure that makes it easy to assemble the mold due to uneven lengths of the ejector pins and alleviates the impact on the ejector pins due to mold clamping.

[Means to solve the problem]

In order to achieve the above object, the lens brim surface is pushed out over the entire circumference by a ring-shaped plate via a button and push-out pin.

Furthermore, in order to prevent impact caused by mold clamping to the extrusion mechanism, a gap is formed at the head of the extrusion pin to limit restraint of the extrusion pin.

Further, in consideration of ease of assembling the extrusion mechanism, the extrusion pin is constructed by piercing the ring plate so that the ring plate can be assembled from the parting surface.

[Effect]

A ring plate was applied to the tip of the extrusion pin so that the lens brim could be extruded all around the circumference.

Therefore, the accuracy of the flatness of the flange is determined only by the accuracy of the ring plate, and therefore there are no cracks or irregularities, and the molding can be performed with high precision.

Furthermore, the gap provided at the head of the ejector pin reduces the impact on the ring plate during the mold closing operation.

Furthermore, the attachment and detachment of the ring plate when assembling the metal is
Since it can be done from the parting surface, damage to the plate can be prevented and the mold can be assembled easily.

Further, the area occupied by the extrusion pin for extrusion may be made small by the ring plate, and the present structure is not limited to the position or size of the extrusion pin.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 is a sectional view showing one embodiment of the present invention of a mold for a plastic lens. The area around one cavity in a multi-cavity mold is shown.

1 is a cavity, which is filled with molten resin to form a molded product (
This is the space in which the lens (lens) is molded. A gate 27 that communicates with the cow cavity and serves as a passage for the molten resin. runner 5
．． A sprue 6 is formed.

Sg, 3 is a fixed insert piece and a movable insert piece that form the cavity 1. The input pieces are sleeves 7t1゜7b, respectively.
and is fixed to the holders 8a, ak with screws 9, etc., for example. Similarly, the sleeve is fixed to the holder, for example by screws 10. Therefore, the fixed insert piece 5@, the fixed sleeve 7a, and the fixed holder 8a are integrated as one fixed side block, and similarly the movable insert piece 3b,
A movable holder 8b is also integrally formed with the movable sleeve 7 as a movable block.

13bg is a fixed mounting plate, 12g is a heat insulating plate, and 15a is a fixed type, which is integrally formed with bolts (not shown) and the like, and is commonly called a fixed frame.

Similarly, 13b is a movable type, 12 is a movable heat insulating plate, 14 is a receiving plate, and 13bh is a movable mounting plate, which are integrally formed with bolts (not shown) and are commonly called a movable frame. Ru. In addition, between the receiving plate 14 and the movable mounting plate 13bb,
A spacer (not shown) is sandwiched and integrated.
A space 15 is formed. For this purpose, push-out plates 17g and 17A, which freely reciprocate while being supported by a support section 15 and 16, are constructed together with the spring 1B. The fixed side block and the movable side block are inserted and fixed into a fixed type and a movable type, respectively. Reference numeral 19 denotes a ceramic ring formed in a ring shape on the parting surface 28 of the sleeves 7m and 7. 20g and 20h are heat medium flow paths formed in the sleeve 7 and the insert piece 3, respectively, and 21 is a fixed amount heat medium flow path formed in the movable housing. 22 is a temperature sensor.

Configuration according to the present invention l! The element will be explained using FIG. 1 and FIG. 2 in detail. FIG. 2 is a cross-sectional view of a model of the main parts of the extrusion mechanism shown in FIG. 1.

The extrusion pin 4 is held by sandwiching its head 4h between the extrusion plates 17g and 17A by a method known in plastic molding, but in the present invention, there is a gap on the left and right sides of the head 4b! The extruded plate 171! The excavation depth and extrusion pin length are determined and configured. Further, the ejector pin is provided with 24 pins for preventing rotation of the ejector pin. The push-out pin passes through the sleeve 7b and the holder 8k, and projects centrally onto the sleeve receiving surface 7c.

A step 4c is provided at the tip 4a of the push-out pin 4, and a screw 4d is integrally formed therein. Ring plate 23f
In C, the through hole 23m for the screw 4d to pass through is
It is formed in multiple locations. Therefore, the ring plate 23 is inserted into the screw 4d and the rotation stopper washer 23 is inserted into the screw 4d.
It is fixed by a nut 26 via.

The ring plate 23 is the gap between the extrusion pin head! Therefore, the sleeve may be in a floating state with respect to the sleeve receiving surface 7C. However, in the tightened state where the fixed ram 15tx and the movable mold 13A are in close contact with each other at the parting 28, the ring plate 23 and the sleeve receiving surface 7C are in close contact with each other.

Further, the positioning of the ring plate is determined by a guide portion 7d formed on the sleeve.

The operation of Venus, which has the above configuration, will be explained.

In FIG. 1, when a desired molten resin material for lenses is injected from the sprue 6, it passes through the runner 5° gate 27 and is filled into the cavity 1. Before performing such an operation, the cavity is closed to the heat medium flow path 20a.

The temperature is controlled to a predetermined temperature by 20A, 21 and a temperature sensor 22.

In this temperature control system, the cavity can be controlled with high precision and efficiency using the heat insulating plates 12g and 12A and the ceramic ring 19.

The resin filled in the middle cavity begins to solidify as cooling progresses, and solidification is completely completed after a predetermined period of time. After solidification, the fixed side and the movable mold are separated into left and right sides from the parting surface 28 by the mold opening operation of the molding machine, and the fixed side of the lens 1a formed in the cavity 1 is released from the mold, and the lens 1a is attached to the movable mold cavity. It is attached. The mold release according to the present invention is performed as shown in FIG.

FIG. 5 is a process diagram showing a model of the deafening operation of the present invention. ■ indicates a state in which the cavity is filled with resin, ■ indicates a state in which the mold is opened after cooling and solidifying, and O indicates a state in which the ejector pin and ring plate move forward and the lens is released from the middle cavity.

The temperature removal step shown by ◯ is a method known in plastic molding in which the extrusion pin 4 moves forward as the movable mold retreats as the mold opens. After reaching the state of θ, the lens 1a
This embodiment shows a concave lens, but in order to smoothly release the lens from the ring plate, it is necessary to remove the contact part 23 between the ring plate and the lens. The basic operation of the present invention is to provide a draft slope of 0 or more, and the present invention will be explained in detail below.

The first feature, as shown in Figure 3 θ, is that the entire circumference of the lens brim is pushed out by a ring plate via an extrusion pin, so there are no irregularities or cracks on the lens brim surface. The smoothness of the flange surface is determined by the flatness of the ring plate, and such flatness can be processed to a degree that satisfies the design specifications.

The second feature is that it is not limited to the size of the brim, and in some cases can be used to release lenses without a brim. That is, if the extrusion location is an extension of the lens shape and is outside the effective diameter, there is no need to intentionally form a flange.

The third feature is that, as shown in FIG. 2, a gap is formed in the extrusion pin head directly connected to the ring plate. This can alleviate excessive impact on the ring plate and extrusion pin during mold closing. In this embodiment, FIG. 1 shows a structure in which the ring plate is automatically returned by a spring 18 after the lens is released from the mold. In this case, the ring plate is a gap! Because of the play, it returns without colliding with the receiving surface of the sleeve at 7°. Thereafter, the fixed plate presses the ring plate during the mold clamping operation, thereby filling the gap between the ring plate and the receiving surface 7c.

The fourth feature is that the ring plate can be assembled from the parting surface side, considering the ease of assembly of Venus. After assembling the movable side frame together using a known procedure, the ring plate can be finally assembled from the parting side. This is because a fixing through hole 23α is provided in the ring plate so that the ring plate 23 can be clamped and fixed. Furthermore, this fixing method has the feature that it is possible to easily monitor the ring plate coming off during the molding operation.

FIG. 4 shows another embodiment of the invention. FIG. 4 is a sectional view of the main part when applied to a convex lens. ring plate 2
3 is basically positioned by the guide part 1c provided on the input piece 3b, but it may also be done together with the guide part 7d of the sleeve.

Further, in this embodiment, the lens flange 2 can be formed with 3 m of fixed side inserts, but even if it is formed on the ring plate 23, no problem will occur in some parts.

In addition, the ring plate is fixed to the extrusion pin 4 with a nut 26, but as shown in Fig. 5, a female screw 4# is formed on the extrusion pin side and the ring plate is fixed with a bolt 26m. It has similar functions.

On the other hand, the ring plate has a structure that does not constitute a launch in this embodiment, but the thickness of the ring plate is t as shown in FIG.
Even if the ring plate is configured as a runner by increasing the ring plate, the same function will not change.However, it is preferable that the thickness t of the ring plate is made thin as long as there is no deformation due to extrusion.

This is because the temperature of the ring plate tends to become unstable as the ring plate moves, and it is difficult to restore the temperature in a short period of time.
This is because the thinner the material, the better. Preferably,
The thickness t is preferably less than the thickness at which the runner can be formed, and 1
5- or less is optimal.

Also, as shown in FIG. 2, gaps are formed on the left and right sides of the extrusion pin head 4h! The gap is preferably configured equally on the left and right sides! The size of is not particularly limited.

Furthermore, as shown in FIG. 1, in this embodiment, the ring-shaped plate can function even if it is made of gold without using a sleeve or holder, as shown in the insert piece. FIG. 5 is a sectional view of a main part showing another embodiment of the present invention. The ring-shaped plate 23 comes into contact with the receiver ISe of the movable amount 13b, and the push-out pin 4 is also provided to penetrate the movable gn1sh.

〔Effect of the invention〕

According to the present invention, the plastic lens is released from the mold by extruding it over the entire brim surface through the ring plate. Therefore, the accuracy of the flange surface can be ensured to be extremely high, making it possible to apply it to lens systems that require high performance.

Full-circumference extrusion using a ring plate causes no deformation due to extrusion and does not require any area for extrusion.In extreme cases, the ring plate and the molded product (lens) only need to have an area for line contact, and the lens It has the effect of removing the brim around the outside. Therefore, the size of the lens can be reduced, which has a great effect on reducing the size and weight of products including the lens system.

In addition, by creating a gap in the head of the ejector pin,
This has the effect of preventing damage to the extrusion mechanism including the ring plate.

In addition, since the ring plate can be assembled from the parting side in the final process, it can be carefully assembled without damaging the ring plate. This allows you to monitor the loosening of the ring plate during the molding process.
This also has the effect of preventing damage to the inserted pieces due to the ring plate falling off.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a molded metal for a plastic lens showing an embodiment of the present invention. Figure 2 is a model sectional view of the extrusion mechanism shown in Figure 1, Figure 3 is a model process diagram showing the extrusion operation of the present invention, Figures 4 and 5 are for plastic lenses showing other embodiments of the present invention. FIG. 6 is a cross-sectional view of a main part of a mold for a plastic lens showing a conventional example. 7 and 8 are sectional views of essential parts of a plastic lens and lens barrel to explain the problem shown in FIG. 1, and FIG. 9 is a plan view of a lens cavity portion showing another example of the conventional example. 1・・・・−・−・・Medium Yaviti 5h・・・・・・・Movable insert piece 4−−−−・−・−・・Extrusion pin 23・・・・・・・Ring plate! +-1+''a0 gap 3a...--Fixed entry piece closed figure porridge 4 figure 47 figure Y33 figure 〒6 figure

Claims (1)

[Claims] 1. Consisting of a fixed frame and a movable frame disposed opposite to the fixed frame and capable of performing mold opening and mold closing operations, the fixed frame includes a fixed mold (13a), A fixed sleeve (7) that holds the fixed insert piece (3a) attached to this fixed mold.
a) and a fixed holder (8a), the movable frame has a movable mold (13b), a movable sleeve (7b) that holds a movable insert piece (3b) attached to this movable mold, and a movable holder (8b). ), and the fixed insert piece (3a), fixed sleeve (7a), movable insert piece (3b), and movable sleeve (7b) form a cavity when the mold is closed. In the plastic lens molding die capable of molding a plastic lens by filling a cavity with molten resin, the movable sleeve (7b)
A ring plate (23) is integrally formed at the tip of the extrusion pin (4) passing through the movable holder (8b), and a gap (g) is formed on the left and right sides of the extrusion pin head (4b) in the mold closed state. What is claimed is: 1. A molding die for a plastic lens, characterized in that the head thereof is provided with a rotation stopper pin (24). 2. Consists of a fixed frame and a movable frame disposed opposite the fixed frame and capable of performing mold opening and closing operations, the fixed frame comprising a fixed mold (13a) and a movable frame attached to the fixed mold. The movable frame has a fixed insert piece (3a), the movable frame has a movable mold (13b) and a movable insert piece (3b) attached to the movable amount, the fixed mold (13a), the fixed insert piece (3a) and movable type (1
3b), the movable insert piece (3b) forms a cavity when the mold is closed, and by filling this cavity with melt resin, a plastic lens can be molded. In the mold, a ring plate (2
3) are integrally configured, and in the mold closed state, a gap (g) is formed on the left and right sides of the extrusion pin head (4b), and a rotation stopper pin (24) is formed on the head. Molding mold for plastic lenses. 3. Provide through holes (23a) in at least two places in the ring-shaped plate (23), and screws (4d) formed in the extrusion pins (4) in these through holes.
3. The molding die for a plastic lens according to claim 2, wherein the ring-shaped plate and the extrusion pin are integrally formed by a nut (26) passing through the ring plate. 4. Provide through-holes (23a) in at least two places in the ring-shaped plate (23), insert bolts (26a) into these through-holes, and insert push-out pins (
3. The mold for a plastic lens according to claim 2, wherein the bolt is screwed into a female thread (4) formed in 4) to integrally constitute a ring-shaped plate.