JPH059139Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial field of application) This invention relates to a mold for forming a disk such as an optical disk.

(Prior art and its problems) Conventionally, the resin passage connecting the sprue and cavity of a general disk molding die has been formed from the sprue side to the cavity side, for example, as described in Japanese Patent Publication No. 58-58214. It tapers toward the surface to minimize disturbances in the flow of the material resin, and
It is designed to be uniformly distributed on the inner peripheral surface of the cavity and injected into the cavity.

Therefore, in this case, the resin that flows into the resin passage first is pushed out by the resin that flows later and is forced into the cavity one after another, so that the resin that has accumulated at the nozzle tip at the initial stage of injection is removed. Once the altered resin, such as the resin that comes into contact with the inner wall surface of the sprue hole or gate land during injection and is cooled to a semi-molten state, enters the resin passageway, it will all be injected into the cavity.

However, since such altered resins have different physical properties, for example, when an optical disk is molded, they have a negative effect on the optical properties of the disk.

For this reason, conventionally, when there is a risk of degraded resin entering the cavity, the sprue shape is enlarged and a resin reservoir is provided in the sprue to store the degraded resin, or the sprue hole is filled with resin at the initial stage of injection. Methods such as slowing down the injection speed during the process to prevent resin that has deteriorated due to contact with the inner surface of the sprue hole from peeling off and being injected into the cavity have been used. In addition, it was necessary to increase the shape of the sprue or slow down the injection speed, and neither of these methods could provide a satisfactory solution.

(Means for solving the problem) This invention forms an annular cavity between a stationary mold and a movable mold, and inserts molding material into the cavity through a sprue hole provided in a sleeve. This disc molding die is characterized in that the resin passage connecting the sprue and the cavity provided between the fixed sleeve and the movable sleeve is a bent resin passage.

(Example) The following will explain the embodiments shown in the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention. In the figure, 1 is a fixed mold, 2 is a movable mold, and 3 is an annular cavity formed when the fixed mold 1 and the movable mold 2 are in a clamped state. A resin material is injected into the inside to form a disk-shaped molded product such as an optical disk.

A sprue bush (fixed sleeve) 4 is fitted into the center of the stationary mold 1, and one end surface of the bush 4 extends to approximately the middle of the cavity 3, and the other end surface is not shown. An injection device (injection nozzle) is in contact with it.

A sprue hole 5 is bored in the center of the sprue bush 4, and the sprue hole 5 enlarges as it moves away from the injection device.

Reference numeral 6 denotes a cut punch (movable sleeve), which is movably fitted into the center of the movable mold 2, and one end surface of the punch 6 faces the sprue bush 4 at a constant distance. It extends to approximately the middle part of the cavity 3.

In the center of the cut punch 6, a protruding pin hole 7 having the same circular shape and a sprue hole 8 which is connected to the sprue bush side of the hole 7 and enlarges as it approaches the sprue bush 4 are bored. .

Thus, a sprue 9 is formed by the sprue hole 5 provided in the sprue bush 4 and the sprue hole 8 provided in the cut punch 6.

Reference numeral 10 denotes a protruding pin that is slidably fitted into the protruding pin hole 7.

On the end face of the sprue bush 4 on the cut punch 6 side, annular projections 11 projecting toward the cut punch 6 on the sprue 9 side and the cavity 3 side, respectively.
and 12 are provided, and both annular projections 1
The protrusion amounts of Nos. 1 and 12 are approximately equal.

On the other hand, on the end surface of the cut punch 6 on the sprue bush 4 side, the sprue bush 4 is provided in the center.
An annular projection 13 is provided that projects to the side.

Therefore, when the molds 1 and 2 are clamped, an annular opening 14 opening toward the sprue 9 side and an annular opening 15 opening toward the cavity 3 side are formed between the facing surfaces of the sprue bush 4 and the cut punch 6. is formed,
Both openings 14 and 15 are connected by a resin passage 16 that is crank-shaped in cross section.

FIGS. 2 and 3 are longitudinal sectional views showing other embodiments of the present invention, and the overall configuration is approximately the same as the embodiment shown in FIG. 1, with sprue bushes 4 facing each other.
The end face shape of the cut punch 6 is different from that of the resin passage 1.
Since the only difference is in the shape of 6, the same components as those in the embodiment shown in FIG.

In FIG. 2, an annular projection 11a projecting toward the cut punch 6 is provided on the sprue 9 side of the end surface of the sprue bush 4 on the cut punch 6 side.

On the other hand, an annular projection 13a is provided on the end surface of the cut punch 6 on the side of the sprue bush 4 on the side of the cavity 3.

Therefore, when the molds 1 and 2 are clamped, an annular opening 14a opening toward the sprue 9 side and an annular opening 15a opening toward the cavity 3 are formed between the facing surfaces of the sprue bush 4 and the cut punch 6. are formed, and both the openings 14a, 15a are connected by a bent resin passage 16a which is bent into a hook shape in cross section.

Further, in the embodiment shown in FIG. 3, contrary to the embodiment shown in FIG.
1b is provided.

The cut punch 6 is provided with an annular projection 13b that projects toward the sprue bushing 4 on the sprue 9 side of the end face of the cut punch 6 on the sprue bushing 4 side.

Therefore, in this embodiment as well, when the molds 1 and 2 are clamped, the sprue 4
An annular opening 14b opening toward the sprue 9 side and an annular opening 15b opening toward the cavity 3 side are formed between the opposing faces of the cut punch 6 and the openings 14b and 15b, and both openings 14b and 15b are bent into a hook shape when viewed in cross section. They are connected by a bent resin passage 16b.

Next, its effect will be explained. The functions of the embodiments shown in FIGS. 1 to 3 are basically the same, so they will be explained together.

First, an injection device (not shown) is operated in a conventional manner to inject material resin into the sprue holes 5, 7. After the resin fills the sprue holes 5, 7, the resin passes through the annular openings 14, 14a, 14b into the resin passage 16. ,16
It is led to cavity 3 via a and 16b.

At this time, in the embodiment shown in FIG.
6 is bent into a crank shape, and in the embodiment shown in FIGS. 2 and 3, resin passages 16a, 1
6b is bent into a hook shape.

Therefore, the resin flows through the resin passages 16, 16a, 16
In the embodiment shown in FIG. 1, four times during passing through b.
Furthermore, in the embodiments shown in FIGS. 2 and 3, 2
3 times, while changing the direction of flow approximately at right angles.
be guided by Therefore, semi-molten resin and the like with poor fluidity stagnate at the corners of the bent portions and do not flow out to the cavity 3 side, and only homogeneous resin with good fluidity is filled into the cavity 3.

(Effect of the invention) According to this invention, degenerated resin such as resin accumulated at the tip of the nozzle during injection or resin that has become semi-molten after contacting the inner wall surface of the sprue hole is injected into the cavity. Because there is no porosity, molded products with uniform material and good optical properties can be obtained.

Moreover, there is no need to enlarge the shape of the sprue or slow down the injection speed in order to prevent the flow of degraded resin into the cavity, as in the past, so the mold (sprue) becomes larger and the molding cycle There are no problems such as the length becoming longer. It has the following effects.

[Brief explanation of drawings]

1 to 3 are longitudinal sectional views showing different embodiments of the present invention. 3... Cavity, 4... Fixed sleeve (sprue bush), 6... Movable sleeve (cut punch), 14, 14a, 14b, 15, 15a,
15b...Opening, 9...Sprue, 16,16
a, 16b...resin passage.

Claims (1)

[Scope of utility model registration request] In a disc molding mold in which an annular cavity is formed between a fixed mold and a movable mold, and molding material is injected into the cavity through a sprue hole provided in the sleeve, the fixed sleeve A disc molding die characterized in that a resin passage connecting a sprue and a cavity provided between a movable sleeve and a movable sleeve is a bent resin passage.