JPS6339057Y2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a structure for improving the exhaust of a resin mold, particularly a mold in which a large number of closely spaced protrusions protrude into the mold space.

(2) Conventional technology and problems Resin molds have a core with a large number of closely spaced protrusions protruding into the mold space. For example, as shown in Figure 1, two-color molding is used to create characters, symbols, etc. In the key top 1 displaying the number 0), the primary molded product is formed so that letters, etc. are stacked on the net-forming area, and then a secondary molded product is formed using a resin of a different color from that of the primary molded product. A mold is used in which a molded product is formed around characters and in closed areas of characters.

FIG. 2 is a side sectional view showing the main structure of the mold and the main steps of the key top 1.

In FIG. 2a, the core 3 fixed to the lower mold plate 2
The upper mold plate 5 for the primary mold has a large number of protrusions 4 protrudingly formed on its upper surface, and constitutes the mold space of the primary mold together with the lower mold plate 2 and the core 3.
A recessed portion 6 for the number 0 is formed on the surface that is in contact with the upper surface of the numeral 0. Therefore, on the upper surface of the primary molded product 7 formed by injecting resin into the mold space, a large number of through holes formed by the projections 4 and the number 0 are stacked and formed on the through hole areas.

In FIG. 2b, after removing the upper mold plate 5 for primary molding, by operating an eject pin (not shown), the primary molded product 7 is moved a predetermined amount above the core 3, that is, slightly above the upper surface of the protrusion 4. be lifted up and held.

Next, as shown in FIG. 2c, when the secondary molding upper molding plate 8, which has a concave portion equal to the outer shape of the key top 1, is stacked and fixed on the lower molding plate 2, the secondary molding space, that is, the number 0 is formed. An outer space of the primary molded product 7 excluding the upper surface and a gap space between the upper surface of the core 3 and the primary molded product 7 are configured. Therefore, when secondary molding resin is injected into the mold space, the resin flows into the closed area of characters (for example, inside the number 0) through the gap space, and the secondary molded product 9 is formed. is completed.

However, in a mold constructed in this way, a large number of protrusions 4 are densely provided on the upper surface of the core 3, so when resin is injected, the air in these parts has no place to escape, and the resin is not filled. The parts were easy to make. As a result, when the end-filling portion occurred in the portion of the letters or the like or the net-like portion below the letters, a portion of the letters, etc. were missing or depressed, resulting in a defective product.
In addition, in a relatively small-capacity resin mold like the key top shown in the figure, the air inside the mold and the gas generated from the resin are generally slowed down as necessary to allow the resin injection conditions to escape through the mating gap of the mold. ing.

(3) Purpose of the invention The purpose of the invention is to eliminate the above-mentioned drawbacks and reduce the product defect rate.

(4) Structure of the device The above object consists of an upper mold plate, a lower mold plate, and a core inserted between the two plates and having a large number of dense protrusions on the upper part that protrude into the mold space. In a resin mold die in which resin mold is injected into the space between the top surface and side surface of the plate and core,
The core has a divided structure in which the upper mold space is vertically divided to separate the dense protrusion formation area, and the mating surface of the division has an exhaust pipe that extends from the upper mold space to the lower end along the dividing surface. This is achieved by a molding die characterized by being provided with a groove.

(5) Example of the invention The present invention is applied to the mold shown in Fig. 2, and Fig. 3 shows a side cross section of the main part of the mold according to one embodiment. The present invention will be explained with reference to FIG. 4, which shows the top surface of the shown split core (core assembly).

In FIGS. 3 and 4, a core assembly 13 formed by combining a pair of cores 11 and 12 has the same outer shape as the core 3 shown in FIG. (same as the lower mold plate 2 in Fig. 2). However, core 12 in contact with core 11
A shallow (for example, about 0.02 mm) rectangular cross-section groove 15 that penetrates vertically and has an appropriate width (for example, about 5 mm) is provided on the bonding surface of the core assembly 13 when the cores 11 and 12 are bonded. This is an exhaust hole that vertically passes through the center of the The upper end of the groove 15 (exhaust hole) opens on the upper surface of the core assembly 13 in which a large number of square protrusions 16 are densely formed in a matrix, while the lower end of the groove 15 (exhaust hole) opens on the lower mold plate 14.
A through hole 18 is drilled in the lower die holder 17 to which the
It is now open to the public.

Therefore, the lower mold plate 14 to which the core assembly 13 is fixed
When primary and secondary molding of the key top 1 is carried out using upper mold plates 5 and 8 as shown in FIG. is ejected from the mold. In addition, when the depth of the groove 15 is about 0.02 mm and the ABS resin that has been degassed by preheating is molded under normal conditions through the gate provided on the mating surfaces of the upper and lower mold plates,
Only a small amount of molten resin entered the groove 15 (exhaust hole), and it did not pose any problem in producing the key top 1 shown in FIG.

(6) Effects of the invention As explained above, according to the invention, the dense protrusions created in the mold are reliably evacuated, and the molten resin completely flows into these parts. This has the practical effect of significantly reducing the defective rate of molded parts having recesses or through holes.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a key top formed by two-color molding, Fig. 2 is a side sectional view showing the configuration of the main parts of the mold for molding the key top and the main steps of manufacturing the key top, and Fig. 3 is a side sectional view of the key top formed by molding the key top. FIG. 4 is a side sectional view of a main part of a mold according to an embodiment in which the present invention is applied to a mold, and FIG. 4 is a top view of the core assembly shown in FIG. 3. In addition, in the figure, 2, 14 are the lower mold plate, 3, 1
1 and 12 are cores, 4 and 16 are protrusions on the upper surface of the core,
5 and 8 are upper mold plates, 7 is a primary molded product, 9 is a secondary molded product, 13 is a core assembly, and 15 is an exhaust groove (exhaust hole).

Claims (1)

[Scope of utility model registration request] It consists of an upper mold plate, a lower mold plate, and a core that is inserted between these two plates and has a large number of dense protrusions on the top that can protrude into the mold space. In a resin molding die in which resin mold is injected into the space between them, the core has a split structure in which the upper mold space is vertically divided so that the dense protrusion formation area is divided, and the mating surface of the division is is a molding die characterized by having an exhaust groove extending from the upper mold space to the lower end along the dividing surface.