JPS6147227A - Injection compression molding die - Google Patents

Abstract

PURPOSE:To prevent the backflow of resin from occurring by a structure wherein a backflow preventer is advanced into a gate part by retreating a movable core by means of the pressure of the resin poured in a cavity. CONSTITUTION:When resin 19 in molten state is filled from a nozzle 18 through a sprue runner 2 and a gate 3 in a cavity 4 (same as cavity 9), an internal piece 5, a connecting pin 7 and an ejecting stand 6 are retreated by means of the pressure in the cavity 4 against a spring 12 by such a distance that the ejecting stand 6 abuts against a rod 11. At this time, a pin 17 implanted in a connecting rod 7 is also retreated, resulting in turning an arm 15 clockwise about a fulcrum shaft 14 and shifting a backflow preventer 13 toward the gate 3. When the backflow preventer 13 advances by the predetermined amount as mentioned above, the tip of the backflow preventer 13 closes the gate 3 mechanically, resulting in cooling and solidifying the resin 19 near the backflow preventer 13 by means of the backflow preventer, the temperature of which is nearly equal to that of the die and lower than that of the resin 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an injection compression mold suitable for molding precision parts such as plastic lenses.

[Background of the invention]

Injection molding, which is known as a type of plastic molding method, uses resin that has been melted and kneaded in a molding machine to be injected into a space inside a mold (
This is a method in which the resin is poured under high pressure into a cavity (hereinafter referred to as a cavity) and cooled over time within the cavity. However, due to the nature of the resin, it always shrinks during cooling, so it is necessary to use precision lenses such as plastic lenses that require high precision. It is not suitable as a molding method for parts, and therefore injection compression molding is generally adopted as a molding method for precision parts.

This injection compression molding method is basically the same as the injection molding method described above, but it is equipped with a compression device such as a hydraulic cylinder in the mold, and the resin injected into the cavity is
Pressure is applied using a compression device, thereby correcting the shrinkage of the resin described above. For example, when a plastic lens is molded using this injection compression molding method, the shape of the lens surface can be transferred as being closer to the cavity part. can. However, when pressurizing the resin with a compression device, the volume of the cavity decreases, and as a reaction to this, a phenomenon occurs in which the resin flows back through the gate, which is the inlet of the resin into the cavity. A means to prevent backflow of resin is required.

As an example of such a resin backflow prevention method, the mold temperature (usually 80 to 100°C) during molding is lower than the resin temperature (usually 210°C).
By utilizing the fact that the resin in the gate part, which is lower than the mold temperature (~230℃) and is easily affected by the mold temperature, solidifies faster than the resin in the cavity part, the solid-cooled resin in the gate part cools the resin from the middle cavity. A method for preventing resin from flowing back into the gate portion is known. However, with this method, it is difficult to balance the solid cooling state of the resin with the timing of pressurizing the cavity. If the cavity is pressurized before the resin at the gate is solid cooled, the resin will flow backwards, causing the cavity to cool. If the cavity is pressurized after the resin has solidified, the shrinkage of the resin cannot be sufficiently compensated for, which is a problem.Therefore, precision parts such as plastic lenses that require shape accuracy on the micron order have a problem. It was unsuitable for molding.

Therefore, when extremely high shape accuracy is required, a backflow preventer that can slide inside the metal and a drive device consisting of a hydraulic cylinder or the like that reciprocates the backflow preventer is installed. A method is adopted in which the gate is mechanically closed. Although this method has the advantage that the backflow of the resin can be reliably prevented by the backflow prevention body, on the other hand, the compression device for pressurizing the cavity inside the metal and the drive device for driving the backflow prevention body are used. The structure of the mold becomes extremely complicated, and the compression device and drive device must be controlled separately, making the control system complicated and making metal molds expensive. It had the disadvantage of becoming This means that in the case of a multi-cavity mold in which multiple products are molded at once with one mold, the compression device and the drive device are each one in total as one cavity is deposited. For example, in the case of a four-cavity mold, a total of eight compression devices and drive devices are required, which poses a particularly big problem.

[Purpose of the invention]

An object of the present invention is to provide a mold for injection compression molding that has a simple structure and can prevent backflow of resin, while eliminating the drawbacks of the prior art described above.

[Summary of the invention]

In order to achieve this object, the present invention includes a backflow preventive body that is retractably provided in the gate part, and a direction changing means that is interposed between the backflow preventive body and the movable core, and When the resin is injected into the gate, the movable core is moved backward by the pressure of the resin, and the backflow prevention body is moved forward into the gate portion through the direction changing means due to the retreat of the movable core.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of an injection compression molding mold according to an embodiment of the present invention, and FIG. 2 is a sectional view of essential parts showing the operating state of the injection compression molding mold shown in FIG. Reference numeral 1 indicates the entire metal wheel, and the mold 1 is composed of a fixed dredge 1a and a movable mold 1b. The fixed type 1g has a tin runner 2, and the movable ff1l
A gate part 3 and a cavity part 4 are respectively provided in b, and the molten resin is injected into the intermediate part 4 through the sprue runner 2 and the gate part 3.

Reference numeral 5 denotes an input piece that is slidably fitted in the vertical direction within the flexible mm1b, and 6 is an extrusion table that is connected to the input piece 5 via a connecting rod 7, and these input pieces 5, extrusion table 6, and connection The rod 7 constitutes a movable core. A step 5a is provided on the periphery of the input piece 5, while a stopper 8 is provided on the movable die 1b, and upward movement of the input piece 5 is regulated by the contact between the step 5a and the stopper 8. ing. Reference numeral 9 denotes a mounting plate fixed to the lower end of the movable ff1lb, and the mounting plate 9 has a hydraulic cylinder 10 attached thereto.
is attached, and a spring 12 is elastically installed between the rod 11 of the cylinder 1o and the push-out table 6.

Reference numeral 13 denotes a rod-shaped backflow prevention body fitted in the movable mold lb so as to be slidable in the vertical direction; 14, a support shaft driven into the movable mold 1b; and 15, rotatably supported by the support shaft 14. The bottle 16 installed at the lower end of the backflow prevention body 13 has a long hole 15a drilled at the left end of the arm 15, and the pin 17 installed at the center of the connecting rod 7 is connected to the arm. They are respectively engaged with elongated holes 15b drilled at the right ends of the holes 15.

With the injection compression mold configured in this way, for example, the outer diameter of the lens is 50 mm, and the center wall thickness of the lens is 5 m.
When molding a concave lens of m, the step 5a is the stopper 8.
The spatial distance d1 between the top of the inserting piece 5 and the lower surface of the fixed mold 1a at the position where it abuts is 4 mm, the spatial distance d2 between the lower surface of the extrusion table 6 and the upper surface of the rod 11 is 2 mm, Further, the length 11 of the perpendicular line drawn from the support shaft 14 to the backflow prevention body 13 is 2Q mm.

Length l of the perpendicular drawn from the support shaft 14 to the connecting rod 7! 40m
Set it to m.

Then, as shown in FIG.
Apply nozzle #18 of the molding machine to runner 2, and
8, the resin 19 in a bath-molten state is filled into the cavity portion 4 through the sprue runner 2 and the gate portion 3. Then,
The inserting piece 5, the connecting pin 7, and the extrusion table 6 are arranged so that the extrusion table 6 resists the spring 12 due to the resin pressure inside the cavity part 4, and the extrusion table 6 presses against the rod 1.
1 and retreats by a distance C==aZ), and therefore,
The minimum spatial distance of the cavity part 4 (center thickness of the lens) is the retraction amount d of the entering piece 5 from the initial setting dx = 4 mm, = 2.
mm is added and changes to di + d* = 6 mm.

At this time, the bottle 17 installed on the connecting rod 7 also retreats by d = 2 mm, so the arm 15 rotates clockwise around the support shaft 14, and the backflow preventer 13 moves upward, that is, in the direction of the gate part 3. Move to. If the forward movement of the backflow prevention body 13 is d8, the inclination angle of the arm 15 is θ, and the backward movement of the inserted piece is dt, then d, = JtX tanθ...
...(1) ds = lIX tanθ
.........), so from equation (1), tanθ-t/it...
(3) is obtained. In the case of this example, l, = 2Qmm
, 12=40 mm, d2=2 mm
Therefore, from equation (3), tanθ= 2/40 =
0.05 is obtained, and by substituting this into equation (2), d3 is obtained.

ds = 20X 0005 = 1 (mm), and the amount of advancement d of the backflow preventer 13 is obtained = 1 mm.

When the backflow preventer 13 moves forward by a predetermined amount in this way, the gate portion 3 is mechanically closed by the tip of the backflow preventer 13, and the resin 19 around the backflow preventer 13 is heated to a gold temperature (usually 80°C). -100°C) and lower than the temperature of the resin 19 (usually 210-230°C)
It is rapidly cooled and solidified. In this embodiment, the depth dimension of the gate part 3 is set to be the same as the forward movement amount ds of the backflow preventer 13 (1 mm), and the structure is such that the gate part 3 is completely closed by the backflow preventer 13. However, the depth dimension of the gate part 3 is set to be somewhat longer than the amount of advance of the backflow preventer 13, and the backflow preventer 13 is fixed at the maximum forward position Wl.
A gap may be formed between the lower surface of a and the upper end of the backflow preventer 13.

In this case as well, the resin 19 located between the fixed mold 1a and the backflow preventer 13 is rapidly cooled and solidified before the other parts by the fixed spatula 1a and the backflow preventer 13, which are lower in temperature than the resin temperature.

In this state, the temperature of the resin 19 in the cavity 4 is somewhat lower than when it is filled. Therefore, next, the hydraulic cylinder l0ICE oil is supplied, and the rod 11 is advanced upward, that is, in the direction of the cavity portion 4. Since the rod 11 is in contact with the lower surface of the extrusion table 6 at this point, the rod 11
1, the inserting piece 5 presses the resin 19 within the cavity portion 4, and the lens surface is compression-molded. Usually, this compression amount is 0.2 to 2. □ mm, and in the case of this example in which polystyrene resin was used as the lens material, the compression i' was set to 1 mm.

In this way, when the entering piece 5 advances by 1 mm in the direction of the cavity 4, the arm 15
The backflow preventer 13 is moved back toward the mounting plate 9 by Q, 5 mm. Thereafter, the fixed mold 1a and the movable mold 1b are separated, and the injection compression molded lens is transferred to the hydraulic cylinder 10.
The entering piece 5 advances further (up to 1 m in this example).
m) is removed from the mold 1 from the cavity part 4.
taken outside.

In one embodiment configured in this way, the distance ll from the support shaft 14 to the backflow prevention body 13 is determined by the distance ll from the support shaft 14 to the connection m.
Arm 15 by making the distance to 7 shorter than 1IIl12.
Since the center of rotation is shifted toward the backflow prevention body 13, the backflow prevention body 13 can be driven with a small driving force of the input piece 5.

In the above embodiment, the movement of the entering piece 5 is controlled by the backflow prevention body 13.
In the above description, the arm 15 having a center of rotation is used as a direction change means for transmitting the information to the user. However, instead of the arm 15, a rack is provided for each of the connecting rod 7 and the backflow preventer 13, and on the other hand, the arm 15 has a rotation center. A pinion that meshes with the rack may be supported, and the direction changing means may be constituted by the rack and the pinion.

Furthermore, the dimensions of each part made of porcelain metal in the present invention are not limited to the above embodiments, and can be changed as appropriate depending on the shape of the lens to be molded.

〔Effect of the invention〕

As explained above, according to the present invention, the backflow preventer can be inserted into the gate part using the driving force of the movable core that retreats due to the resin pressure in the cavity part, so a simple mold structure can be used. , it is possible to prevent backflow of resin during pressurization.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an injection compression molding mold according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of essential parts showing the operating state of the injection compression molding mold shown in FIG. 1. 1...Mold, la...Fixed, 1b.
... Range of motion, 2 ... Sprue runner, 3
...Gate part, 4...Cavity part,
5... Input piece, 6... Extrusion stand, 7...
...Connecting rod, 8...Stopper, 9...
・Mounting plate, 10...Hydraulic cylinder, 11...
...Rod, 12...Spring, 13...
・Backflow prevention body, 14... Support shaft, 15...
・Arm, 15a, 15b... Long hole, 16.1
7...Pin, 18...Nozzle, 19.
...Kizukiji. O・1Figure 11 12 lO Figure 2

Claims (2)

[Claims] (1) A mold for injection compression molding that includes a cavity part, a gate part communicating with the cavity part, and a movable core that can move back and forth, and compresses molten resin injected into the cavity part from the gate part with the movable core. A backflow preventive body provided retractably in and out of the gate portion; and a direction changing means interposed between the backflow preventive body and the movable core, wherein the backflow preventive body controls movement of the movable core. 1. A mold for injection compression molding, characterized in that the mold is configured to move in a direction opposite to the movable core in synchronization with the movement of the movable core. (2) Claim (1) is characterized in that the direction changing means is constituted by an arm having a rotation center, and the backflow prevention body and the movable core are respectively connected to both ends of the arm. A mold for injection compression molding.