JPH03264320A - Mold for injection molding - Google Patents

Abstract

PURPOSE:To release easily without damaging an optical surface of a molded product by making an optical molded surface and a structural reference surface inclined in the releasing direction and providing a cavity with the inclination angle. CONSTITUTION:A mold 1 for injection molding consists of a fixed side template 2 and a movable side template 3. An insert block 4 is fitted and fixed on a recessed section 2a of the fixed side template 2 by a pin 5 and an insert block 6 is fitted and fixed on a recessed section 3a of the movable side template 3 by the pin 5, while an insert block 7 is fitted freely slidably. A molded surface 6a of the insert block 6 is formed in parallel with the regular releasting direction A but inclined by the angle theta of 4 deg.. An ejector bar 8 is connected with the insert block 7 and constituted movable up and down freely, and its molded surface 7a is formed inclining by the angle theta of 4 deg. corresponding to the inclination of the insert block 6 in order to secure a square section of a caivty. Injection molding is carried out by using the mold for injection molding of above-said constitution to manufacture a molded product without damaging the optical surface.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an injection mold for optical elements.

[Prior Art] Conventionally, structural reference planes 31a and 90 as shown in FIG.
In the case of a molding tool 31 having an optical surface 31b which is parallel to the M-type direction A, the important optical surface 31b will be scratched due to the friction and stress generated during mold release. In order to eliminate this drawback, the slide insert 34 angular pin 35. bank up 36
A method is generally used in which the optical surface 31b and the slide insert 34 are separated from each other by a slide mechanism including a slide presser 37 and the like.

Furthermore, the following inventions have been disclosed in cases where angular intersection of the optical surfaces is permitted due to the function of the forming tool.

For example, the invention described in Japanese Utility Model Application Publication No. 1-67627 includes:
A method has been proposed in which a mold is provided with a punching slope to prevent problems during mold release.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology, which uses a slide mechanism to solve the mold release problem, not only complicates the structure of the mold and increases the manufacturing cost of the mold, but also requires high-precision molding, especially for optical moldings. In the case of molded products that require high angular accuracy, problems with backlash and positioning reproducibility due to clearances B and C (see Figure 5), which are necessary for the sliding of the movable part of the slide mechanism itself, may occur.
The drawback was that the accuracy was one rank lower than when there was no slide mechanism.

Furthermore, the invention described in the above-mentioned Japanese Utility Model Publication No. 1-67627 is an optical molded body that requires angular accuracy itself, and no consideration is given to the surface accuracy of the optical surface.

Therefore, the present invention solves the drawbacks in the prior art, and
The purpose is to provide inexpensive and simple molds.

[Means and effects for solving the problems] The present invention provides an injection mold for an optical molded article in which the angle between the optical molding surface and the structural reference plane is a right angle. The reference plane is inclined in the die cutting direction, and the cavity has an inclination angle. Further, in the injection mold in which the cavity has an inclination angle, an uneven portion is formed in the mold, and a side surface of the uneven portion has a slope equal to or greater than the above-mentioned inclination angle. Furthermore, in the injection mold in which the cavity has an inclination angle, the side surface of the uneven portion formed in a direction perpendicular to the structural reference plane has a taper of at least twice the inclination angle.

According to the present invention, by tilting the entire cavity of the injection mold, it is possible to easily release the molded product without damaging the optical surface of the molded product.

〔Example〕

Hereinafter, embodiments of the injection mold according to the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a partially omitted cross-sectional view showing a first embodiment of the present invention.

Reference numeral 1 denotes an injection mold, and the injection mold 1 is made up of a fixed mold plate 2 and a movable mold plate 3. An insert 4 is fitted and fixed in the recess 2a of the stationary template 2 with a pin 5. An insert 6 is fitted and fixed to the recess 3a of the movable mold plate 3 by a pin 5, and an insert 7 is slidably fitted therein. The molding surface 6a of the insert 6 is normally parallel to the mold release direction A, but is formed to be inclined by an angle θ of 4°. A protruding rod 8 is connected to the insert 7 and can freely move up and down.
In addition, the molding surface 7a is formed to be inclined by an angle θ of 4'' in accordance with the inclination of the insert 6 in order to ensure a right angle portion of the cavity.

When injection molding was carried out using an injection molding die that was prepared according to the above authorities, a molded product with no scratches on the optical surface was easily obtained.

In this example, the inclination angle θ of the cavity is set to 4″′.
However, the present invention is not limited to this, and the angle of inclination may be in the range of 1° to 10°, and an angle of 3° to 5″ is particularly suitable for releasing from the mold without stress. ing.

(Second Embodiment) FIGS. 2a and 2b are partially enlarged cross-sectional views showing a fixed side insert according to a second embodiment of the present invention.

FIG. 2a shows a molded product 21 formed by providing a concave portion in the stationary side insert 4 in the first embodiment. When injection molding is performed with a molded product 21 having additional functional parts such as concave portions and convex portions simply tilted, the side surface 22a of the overhang portion 22 becomes an obstacle to mold release, as shown in FIG. 2a. (undercut) occurs (○ angle), to remove this obstacle,
As shown in FIG. 2, the side surface 22a of the overhang portion 22, which serves as an undercut, is formed into a side surface 22b having an inclination (an angle of ■) of θ angle (4°) or more.

According to this embodiment, it is possible to eliminate an undercut portion that becomes an obstacle to mold release, and structural functions such as lips, bosses, and holes can be added very easily.

(Third Embodiment) FIGS. 3a and 3b are side views showing a molded article according to a third embodiment of the present invention.

FIG. 3a shows a molded product 23 in which a convex boss used for positioning when attaching the molded product is integrally formed on the overhang portion 22 of the molded product 21 in the second embodiment. If injection molding is performed with the molded product 23 simply tilted, an obstacle (undercut) will occur during mold release. In order to eliminate this problem, as shown in FIG. 3, the boss serving as the undercant is formed with a taper of 2θ (8°) or more.

Hereinafter, the functions and effects are the same as those of the second embodiment, and the explanation of the functions and effects will be omitted.

[Effect of the invention] As described above, according to the injection mold according to the present invention,
It prevents scratches and stress caused by rubbing against each other during mold release, and allows mold release without distorting the bottom-shaped optical plane. Furthermore, since no sliding parts such as slides are required, the mold has a simple structure and is inexpensive.

Furthermore, since there is no play in the fit, the angular accuracy, which is most important for optical molded bodies, is not impaired.

[Brief explanation of drawings]

FIG. 1 is a partially omitted cross-sectional view showing a first embodiment of an injection mold according to the present invention, FIGS. 2 a and b are partially enlarged cross-sectional views showing the second embodiment, and FIG. a and b are the same third
4 and 5 a and b show a conventional example, FIG. 4 is a perspective view, FIG. 5 a is a front sectional view, and FIG. 5 is a side sectional view. 1... Injection mold 2... Fixed side template 3... Movable side template 4.6, 7.21... Insert 5... Bin 8... Extrusion rod 22. ... Overhang part 23 ... Molded product 24 ... Boss

Claims (3)

[Claims] (1) In an injection mold for an optical molded object in which the angle formed by the optical molding surface and the structural reference surface is a right angle, the optical molding surface and the structural reference surface are inclined in the mold removal direction, and the cavity An injection mold characterized by having an inclined angle. (2) In the injection molding mold in which the cavity has an inclination angle, an uneven portion is formed in the mold, and a side surface of the uneven portion has a slope greater than the inclination angle. 1. The injection mold according to 1. (3) In the injection mold in which the cavity has an inclination angle, the side surface of the uneven portion formed in a direction perpendicular to the structural reference plane is configured to have a taper of twice or more the inclination angle. The injection mold according to claim 1 or 2.