JPH07117088A - Apparatus and method for molding plastic concave lens - Google Patents

Abstract

PURPOSE:To provide a mold apparatus capable of molding a plastic concave lens of high quality by perfectly preventing the generation of weld at the time of the injection of a molten resin into a cavity. CONSTITUTION:An induction input 50 is allowed to advance and retreat from the position opposed to the gate 35 of the peripheral side part of the cavity 30 between a fixed input 6 and a movable input 13 with respect to the cavity 30 by a drive device 55 and a molten resin is injected into the cavity 30 in such a state that the induction input 50 is allowed to protrude. After the resin strikes against the leading end of the induction input 50, the induction input 50 is allowed to retreat to the peripheral side part of the cavity and, thereafter, the movable input 13 is allowed to advance. By this constitution, the resin penetrating in two directions of the central and peripheral parts of the cavity can fill the induction input retreat region in the cavity at the almost same time. Therefore, the generation of weld can be perfectly prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for molding a plastic concave lens, and in particular, at the time of injecting molten resin into a cavity, the movable insert in the movable side mold is retracted to increase the thickness of the cavity. In addition, the present invention relates to a mold device in which the movable insert is advanced after injection to compression-mold a plastic concave lens of a specified shape, and a molding method using the mold device.

[0002]

2. Description of the Related Art When molding a plastic concave lens L having a central portion (on the optical axis) having a thickness t smaller than a peripheral portion thickness T as shown in the sectional view of FIG. As shown, the pair of fixed and movable molds 101 and 102 are clamped, and the cavity 106 for molding the concave lens L is provided between the inserts 103 and 105 built in the respective molds 101 and 102. To form. Then, the molten resin supplied through the runner 107 is injected and injected into the cavity 106 from the gate 109 located on the peripheral side of the cavity to compression-mold the concave lens L.

However, in this way, the cavity 10
When the molten resin is injected and injected into the cavity 6, the concave lens forming cavity 106 has a thin central portion and a thick peripheral portion.
As shown in the explanatory view of FIG. 8 (a), the injected molten resin 110 is divided into two directions along the peripheral portion having a low resistance and quickly enters, and the molten resin 110 is directed toward the central portion having a large resistance from the peripheral portion. Enter slowly. As a result, as shown in the explanatory view of FIG. 8B, the gate 10 in the cavity 106 is
A weld 111 is generated in a region facing 9.

For example, the diameter is 80 mm and the thickness of the central portion is 1.5.
When a molten resin is injected and injected into a cavity for forming a concave lens having a thickness of 0.5 mm and a peripheral portion having a thickness of 6.5 mm, a weld having a diameter of about 1/10 of the cavity is generated.

Therefore, conventionally, in order to mold a concave lens without generating a weld, the thickness of the cavity is expanded at the time of injection and injection of the molten resin into the cavity, and the thickness of the cavity is reduced after the injection. A mold device is used in which a plastic concave lens having a specified shape is compression molded.

For example, in the injection compression molding die device disclosed in Japanese Patent Laid-Open No. 61-66623, as shown in the schematic diagram of FIG. 9, the insert 1 to be built in the movable die 102.
When 05 is a movable insert capable of advancing and retracting, when the molten resin is injected and injected into the cavity 106, the movable insert 105 is retracted to increase the thickness of the cavity 106, and the movable insert 105 is inserted after the injection. The cavity 106 is advanced to reduce the thickness, and a plastic concave lens having a designated shape is compression-molded.

That is, in this injection compression molding die device, when the molten resin is injected, the movable insert 105 is retracted to increase the thickness of the cavity 106, so that the molten resin injected into the cavity 106 is Make it possible to enter the direction of the central part at a speed not much different from the direction of the peripheral part,
This is to prevent the occurrence of welds.

[0008]

However, in actuality, when molding the above-mentioned concave lens having a diameter of 80 mm, a central portion thickness of 1.5 mm and a peripheral portion thickness of 6.5 mm, the cavity thickness is Even if the molten resin is expanded by 3.5 mm at the time of injection to have a central portion of 5 mm and a peripheral portion of 10 mm, as shown in the explanatory view of FIG.
The molten resin 110 injected and injected into the resin 6 has a tip edge that curves like curves 110a to 110e in the figure, and a weld 111 of about one-tenth the diameter of the cavity 106 remains.

As described above, in the above-mentioned conventional injection compression molding die device, it is impossible to completely prevent the generation of welds, and it is difficult to mold a high-quality plastic concave lens.

The present invention has been made in order to solve this problem, and it is possible to completely prevent the generation of weld when the molten resin is injected and injected into the cavity and form a high quality plastic concave lens. Molding die equipment, which can
Another object of the present invention is to provide a molding method using the molding die device.

[0011]

A molding die apparatus according to the present invention has a cavity (30) formed between a fixed insert (6) and a movable insert (13), which is located on the circumferential side of the cavity. Part (50) that moves forward and backward from the position facing the gate (35) of the part, and the guide part is projected into the cavity when the molten resin (60) is injected, and reaches the cavity peripheral side part during compression molding. And a drive means (55) for retreating.

Further, the molding method according to the present invention is a molding method using the molding die device having the above-mentioned structure, in which the movable insert (13) is retracted and the guide insert (50) is projected. Molten resin (60) in the cavity (30) at
After the molten resin hits the tip of the protruding guide insert, the guide insert is retracted to the cavity peripheral side, and then the movable insert is advanced to move the plastic of the specified shape. It is characterized in that a concave lens is compression molded.

[0013]

In the molding die apparatus and molding method having the above construction,
The shape of the guide insert (50) is changed to the enlarged cavity (3
If it is set appropriately according to the shape of (0), the gate (3
The molten resin injected from 5) into the cavity and progressing in the peripheral direction is stopped at the side of the guide insert until the molten resin advancing in the central direction hits the tip of the guide insert, and , The induction insert (50) to the cavity (30)
When the resin is retracted to the peripheral side, the molten resin from the two directions of the central portion and the peripheral portion almost simultaneously fills the region in which the induction nest is retracted in the cavity. Therefore, no weld is generated in the cavity.

The reference numerals in parentheses refer to the drawings and do not limit the structure of the present invention.

[0015]

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

FIG. 1 is a side sectional view showing the structure of a molding die apparatus according to an embodiment of the present invention.

As shown in the figure, this molding die apparatus is provided with a pair of a fixed side die 1 and a movable side die 2 which are clamped to each other, and the fixed side die 1 and a mold plate 3 are provided. The fixing plate 6 and the mounting plate 5 are formed to have a built-in structure. In the case of this embodiment, so that a plurality of concave lenses can be simultaneously molded,
A plurality of fixed inserts 6 are built in. A sprue 7 is embedded in the center of the stationary mold 1.
The sprue 7 has a runner 9 formed along the central axis thereof, and is held by a sprue retainer 10 fixed to the rear surface of the mounting plate 5 so as not to come off.

On the other hand, the movable mold 2 is formed by a mold plate 11 and a receiving plate 12 having a movable insert 13 built therein.
As for the movable inserts 13, a plurality of movable inserts 1 are built in corresponding to the fixed inserts 6 of the fixed mold 1, and each movable insert 1
3 is incorporated so as to face each fixed insert 6 and move back and forth. A mounting plate 19 is mounted on the rear surface of the receiving plate 12 via the spacer block 15, the ejector sub-plate 16 and the ejector plate 17.

Further, the movable side mold 2 has a plurality of ejector pins for nesting with a return spring 21 for advancing and retracting the main ejector pin 20 located at the center and the movable nests 13 located around the main ejector pin 20. 22 are provided so as to be able to move forward and backward through the receiving plate 12, the ejector sub-plate 16, the ejector plate 17, and the mounting plate 19. These ejector pins 20 and 22 are connected to a drive mechanism (not shown).

A spool pin 18 is screwed into the ejector plate 17 and is planted.
Is inserted into a hole 18a penetrating the mold plate 11 and the mold plate 12, and a cold slag pool C is formed at the tip thereof. Therefore, at the time of filling the resin, the resin that has hardened at the tip of the nozzle is first injected into the pool C, and the resin in a sufficiently molten state passes through the runner 9a and the gate 35 and flows into the cavity 30. .

Then, the operation of the main ejector pin 20 causes the ejector plate 17 to move (to the left in FIG. 1).
Since the ejector sub-plate 16 is also movable by moving forward, the connecting pin 3 connected to the movable insert 13
8 is pushed up (the connecting pin 38 and the insert ejector pin 22 are at the same position in the figure, but the insert ejector pin 22 is different in position from the connecting pin 38 with an angle difference). The child 13 and the spool pin 18 are
It moves by the same amount as the stroke of the main ejector pin 20. This operation is performed when the resin filled in the cavity 30 is applied with sufficient pressure so as not to escape the resin that is trying to flow backward from the cavity 30 toward the runners 9a, 9 and when the resin solidifies and the molded product is formed. It is done when sticking out.

Further, the insert ejector pin 22 is inserted into a hole penetrating the ejector plate 17 and the mounting plate 19, supports the ejector sub-plate 16 and advances only the movable insert 13. This nesting ejector pin 2
While the movable insert 13 is moving forward by 2, the main ejector pin 20 is operated to operate the spool pin 18 to apply pressure from the side to the resin in the reservoir C and the runner 9a and the resin in the cavity 30 through the gate 35. Therefore, it is preferable that the main ejector pin 20 and the nesting ejector pin 22 have separate drive mechanisms.

When the fixed mold 1 and the movable mold 2 are clamped, a cavity for molding a concave lens is formed between the fixed insert 6 and the movable insert 13 of the molds 1 and 2. Thirty
Is formed. In FIG. 1, the movable insert 13 is in a retracted state, and thus the cavity 30 is in a state where the concave lens having the designated shape is thick and the interval is wide. A plurality of runners 9a communicating with the runner 9 of the sprue 7 and the runners 9 are provided between the template plates 3 and 11.
A plurality of gates 35 that communicate a with the peripheral side of each cavity 30 are formed.

In the molding die device according to the present invention, in addition to the above configuration, with respect to the cavity 30 formed between the fixed insert 6 and the movable insert 13, the above-mentioned peripheral side portion of the cavity 30 is formed. A guide insert 50 that advances and retracts from a position facing the gate 35, and a drive device 55 such as a solenoid that drives the guide insert 50 are provided corresponding to each cavity 30. In the case of the present embodiment, the guide insert 50 has a plate shape. In the illustrated example, the driving device 55 is fixed to the outer surface of the mold plate 3 of the fixed-side mold 1 (it can also be fixed to the outer surface of the mold plate 11 of the movable-side mold 2), and the driving device 55 thereof. Induction nest 50 extended from the
Can be slid through the parting line between the fixed side and movable side mold plates 3 and 11, along one parting line, and on the other side through a groove-shaped guide. It is inserted in the cavity 30. Then, the drive device 55 operates so that the guide insert 50 is projected into the cavity 30 when the molten resin is injected into the cavity 30 and is retracted to the peripheral side portion of the cavity 30 during compression molding, as described later. .

Next, regarding the molding method according to the present invention, in which a plastic concave lens is compression-molded by using the molding die apparatus having the above-mentioned configuration, the sequence operation diagram of FIG. 2 and FIGS.
This will be described with reference to the state explanatory diagrams of FIGS. 3 (a) and 5 (b) are a plan view and a side sectional view showing the same state.

First, the fixed side and movable side molds 1 and 2 which are in an open state are moved by moving the mold clamping device, and the movable side mold 2 is moved to close a preset mold clamping. The mold is temporarily stopped at the position to perform the mold locking and locking, and the mold is closed with a gap so that the mold is completely closed (mold clamping) (S1 to 3). At this time, the movable insert 13 is in the retracted position, and the space between the cavities 30 formed between the fixed insert 6 and the movable insert 13 is large. In this state, the drive device 55 is operated to move the guide insert 50 forward (S
4) As shown in FIG. 3, a predetermined amount D is projected into the cavity 30.

A protrusion amount D and a width W of the guide insert 50.
Is properly set so that the guide insert 50 can act as described later. Further, the thickness of the guide insert 50 is as thick as possible within a range where the guide insert 50 can protrude into the expanded cavity 30 by the predetermined protrusion amount D, and is close to the fixed insert 6 and the movable insert 13 (Fig. 3 (b)).

After the advance of the guide insert 50, the molten resin is injected from the outside of the mold through a nozzle (not shown) in the injection unit, the molten resin is supplied through the runners 9 and 9a, and the inside of the cavity 30 is supplied from the gate 35. (S5). Then, as shown in FIG. 4, after the molten resin 60 that has entered the cavity 30 flows and hits the tip of the protruding guide insert 50, the drive device 55 is operated, and as shown in FIG. Introducing the insert 50 into the cavity 3
It is retracted to the peripheral side of 0 (S6). This induction nest 50
Whether or not the molten resin has come into contact can be determined by directly connecting the induction insert 50 and a sensor to detect the temperature or pressure, but can also be estimated by the injection capacity of the amount of filled resin. After the retreat is completed, the injection of the molten resin 60 is stopped (S7). The operation of the guide insert 50 at this time will be described below.

Now, assuming that the thickness of the cavity 30 in the expanded state is 5 mm in the central portion and 10 mm in the peripheral portion, the direction of the peripheral portion of the molten resin 60 injected into the expanded cavity 30. The ratio of the speed of going to and the speed of going to the center is about 2 to 1. In other words,
The distance from the center to the outer circumference is represented by πR / 4, where R is the diameter, and the center is delayed by about R / 10, which makes welds easy to occur. That is, the speed ratio between the outer circumference from the center and the center is (4R / 10) / (πR / 4) ≈1 /
It can be represented as 2. Therefore, in this case, as shown in FIG. 4, if the width W of the guide insert 50 is set to four times the protrusion amount D, the molten resin that has proceeded in the peripheral direction advances in the central direction. Until the molten resin hits the tip of the guide insert 50, it is dammed by the side part of the guide insert 50, part of it is wrapped around to the tip side, and the guide insert 50 is retracted to the peripheral side part of the cavity 30. At times, the molten resin from two directions, the central part and the peripheral part, is almost at the same time.
The guide insert 50 flows into 0 so as to fill the area where the guide insert 50 is retracted. Therefore, in the cavity 30, the molten resin is
In particular, since the resin on the tip side of the guide insert 50 flows toward the outer peripheral side thereof and comes into contact with the drawn guide insert 50,
Weld does not occur.

After retracting the guide insert 50 to the peripheral side portion of the cavity 30 in this manner, the mold clamping device 1
2 is clamped (S8), the ejector pin 22 for nesting is operated to move the movable nest 13 forward (S8).
9) Align the intervals of the cavities 30 with the concave lens of the specified shape. After the mold clamping is completed (S10), the pressure is maintained (S11), and in some cases, the main ejector pin 20 is operated to move the spool pin 18 forward to press the resin flowing from the gate 35 to the runner 9a. , Hold the pressure sufficiently. After the pressure holding is completed (S12), resin plasticization / measurement of the next shot is started (S13), and the molten resin is cooled and solidified in the cavity 30 (S14). Then, the locking of the mold clamping in the mold clamping device is released (S
Along with 15), the mold clamping device is operated to start the mold opening (S16), and after the mold opening is stopped (S17), the main ejector pin 20 is moved forward to move the movable insert 13 and the spool pin 18 forward to solidify. The formed product is stored in the reservoir C, the runner 9,
9a and the gate 35 are ejected and released (S18). This completes a series of compression molding operations for the plastic concave lens.

As described above, the protrusion amount and width of the guide insert 50 are set in consideration of the slow difference in the flow velocity of the resin, so that they are injected and injected from the gate 35 into the cavity 30 and the peripheral portion. The molten resin that has advanced in the direction and the molten resin that has traveled in the direction of the central portion
It is possible to fill the region facing to the same at almost the same time irrespective of the difference in slow speed, thereby completely preventing the occurrence of weld.

[0032]

As described above, according to the molding die apparatus and the molding method of the present invention, after the molten resin is injected into the cavity, the resin flows at the confluence of the cavity. Since the difference in slow speed is suppressed by the guide insert and the flow is merged, it is possible to completely prevent the generation of welds and mold a high-quality plastic concave lens.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of a molding die device according to an embodiment of the present invention.

FIG. 2 is a sequence operation diagram illustrating a molding method according to an embodiment of the present invention.

3 (a) and 3 (b) are state explanatory views of a molding die device according to an embodiment.

FIG. 4 is another state explanatory view of the molding die device according to the embodiment.

5 (a) and 5 (b) are explanatory views showing another state of the molding die device according to the embodiment.

FIG. 6 is a sectional view of a concave plastic lens.

FIG. 7 is a side sectional view showing a configuration of a molding die device in a conventional example.

FIG. 8 is an explanatory view for explaining the movement of the molten resin injected and injected into the cavity in the conventional example.

FIG. 9 is a schematic configuration diagram illustrating another conventional example.

FIG. 10 is an explanatory view explaining the movement of the molten resin injected and injected into the cavity in another conventional example.

[Explanation of symbols]

 1 Fixed Side Mold 2 Movable Side Mold 6 Fixed Insert 9, 9a Runner 13 Moveable Insert 30 Cavity 35 Gate 50 Induction Insert 55 Drive Device (Drive Means)

Claims (2)

[Claims] 1. A fixed-side mold having a fixed insert and a movable-side mold having a movable insert that moves forward and backward to face the fixed insert. The mold is clamped. A cavity is formed between the fixed insert and the movable insert, and in the state where the movable insert is retracted, the molten resin supplied through the runner into the cavity is placed in the cavity peripheral side portion. In a mold device for injecting and injecting from the above, and after the injection, the movable insert is advanced to perform compression molding of a plastic concave lens of a specified shape, in the cavity formed between the fixed insert and the movable insert, A guide inserter that advances and retreats from a position facing the gate on the peripheral side of the cavity, and a drive means that causes the guide inserter to protrude into the cavity when injecting the molten resin and retract to the peripheral part of the cavity during compression molding. , The molding die apparatus of the plastic concave lens which comprising the. 2. A method of molding a plastic concave lens using the molding die device according to claim 1, wherein the movable resin is retracted and the guiding resin is projected so that the molten resin is injected into the cavity. After injection and injection, the molten resin hits the tip of the projecting guide insert, the guide insert is retracted to the cavity peripheral side, and then the movable insert is advanced to advance the plastic concave lens of the specified shape. A molding method comprising: compression-molding.