JPH0324888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a two-color mold, and particularly to a primary mold for displaying characters, symbols, etc. on the curved surface of a molded product.

(b) Background of the technology In a keyboard equipped with a large number of pushbutton switches, the input display for each keytop is generally formed by forming the keytop with a two-color mold, and is clearly indicated on the keytop itself, but the input display for each keytop is Concave or cylindrical surfaces are often used.

(c) Prior Art and Problems Figure 1 is a perspective view A showing an example of a two-color molded key top, and a perspective view B showing its primary molded product.

In FIG. 1, for example, a key top 1 with an input display (numeral 5) clearly displayed in black on a gray background is made by molding a primary product 2 with a protrusion 2a with a numeral 5 protruding from the top surface using black resin. A gray resin surface layer 3 is molded on the side surface of the primary product 2 and on the upper surface around the number 5.

FIG. 2 is a side cross-sectional view showing the main structure of the mold for molding the key top 1, FIG. 2A is the primary molding mold for molding the primary product 2, and FIG. This is a secondary molding die for molding.

In Fig. 2A, 11 is a convex template, 12 is a concave template, 13 is a core, and 14 is a template 12 and a core 13.
The mold plates 11 and 12 and the core 13 constitute a cavity 15, and the core 13 has a groove 13a carved therein for forming a protruding number 5. Therefore, by clamping the templates 11 and 12 with appropriate pressure and injecting black molten resin into the cavity 15 through a runner and gate (not shown), the primary product 2 is molded.

In FIG.
1 and 16 constitute a cavity 17 of the key top surface layer 3. Therefore, when gray molten resin is injected into the cavity 17 through a runner and a gate (not shown), the surface layer 3 is molded and the key top 1 is formed.
is completed.

In the mold configured in this way,
The conventional core groove 13a was formed using an end mill having a diameter equal to the thickness of the letters, numbers, etc. to be engraved, 0.3 to 0.73 mm, or the minimum width. Therefore, when the display surface 1a of the key top 1 is not a flat surface but, for example, a spherical concave surface, a cylindrical convex surface, or a pyramid-shaped concave surface, the resin forming the surface layer 3 may cover a portion of the upper surface of the display protrusion 2a. Ta.

Figures 3 and 4 are side sectional views for explaining the conventional method of cutting grooves for forming display protrusions into a mold;
The figure is a side sectional view showing a state in which the line width (thickness) of numbers, etc. is narrowed by using the mold according to the conventional method.

In FIG. 3, 18 is a core corresponding to the above-mentioned core 13, 19 is an end mill for cutting a groove corresponding to the above-mentioned groove 13a, and a two-dot chain line 20 is an imaginary curve showing a spherical key top display concave surface. It is. and,
For example, when the end mill 19 is moved in the thickness direction of the paper, one tip of the end mill 19 is curved 2.
0, while its opposite tip deviates from the curve 20 by a dimension A.

In FIG. 4, 21 is a core corresponding to the above-mentioned core 13, 22 is an end mill for cutting a groove corresponding to the above-mentioned groove 13a, and a chain double-dashed line 23 is a part of a pyramid-shaped key top display concave surface. This is an imaginary diagonal line indicating For example, when the end mill 22 is moved in the same manner as the end mill 19 described above, the end of the end mill 22 opposite to the end in contact with the diagonal line 23 will be separated from the diagonal line 23 by the dimension B.

Therefore, in a primary product molded using a mold incorporating the core 18 or 21, a part of the upper surface of the display protrusion corresponding to the aforementioned protrusion 2a comes off from the key top display surface in a wedge-like manner. It is formed by Therefore, for such a primary product, that is, a primary product where A and B are approximately 0.1 mm maximum in a normal key top,
When the surface layer (corresponding to the above-mentioned surface layer 3) is formed by molding, as shown in FIG.
The resin forming 5 flows in and covers the part.

As a result, there was a drawback that the line width (thickness) of the input display became narrow and blurred at the flow-in portion, and sometimes was interrupted.

(d) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned problems, clarify the display of letters, numbers, etc., and improve the display quality.

(e) Structure of the Invention The above object is to provide two-color molding in which the upper surface of protrusions such as letters and symbols protruding from the surface of a mold formed by primary molding is exposed to the curved surface of a mold of a different color formed by secondary molding. In a two-color mold for forming the mold, the groove of the primary mold that forms the protrusion protruding from the mold surface has a diameter smaller than the width of the protrusion such as the letter or symbol, and is formed by secondary molding. This is achieved by a two-color molding die that is cut with an end mill that moves in three dimensions following the curved surface of the mold.

(f) Embodiments of the invention Examples of the invention will be described below with reference to the drawings.

FIG. 6 is a side sectional view for explaining an embodiment in which grooves for display protrusions are cut in a core corresponding to the core 13 described above by the method of the present invention, and FIG. A side sectional view for explaining another method of cutting, and FIG. 8 shows a part of a key top obtained by performing secondary molding on a primary product molded using the core shown in FIG. 6. FIG.

In FIG. 6, 31 is the core of the primary molding die;
32 is an end mill with a diameter of 0.12 mm, 33 is a groove cut by the end mill 32 to form a display protrusion, and the two-dot chain line 34 is an imaginary curve on the display surface corresponding to the two-dot chain line 20 mentioned above. It is moved along the curve 34 in the width direction of the groove 33 (horizontal direction in the drawing). Therefore, the dimension C at which the bottom surface of the groove 33 deviates from the curve 34 is, for example, when the width of the groove 33 is about 0.6 mm, as shown in FIG. Approximately 1/ of the dimension A of
5 (for example, 0.02mm).

In FIG. 7 using the aforementioned end mill 32, 41 is a core corresponding to the aforementioned core 21, and 42 is a core corresponding to the aforementioned core 21.
is a groove corresponding to the above-mentioned groove 33, the two-dot chain line 43 is an imaginary diagonal line on the display surface corresponding to the above-mentioned two-dot chain line 22, and the end mill 32 forms the groove 42 in a stepped manner by using the diagonal line 43.
It is moved in the width direction (horizontal direction in the drawing).

Therefore, the bottom surface of the groove 42 has a step-like shape, and the step D is, for example, when the width of the groove 42 is about 0.6 mm.
As shown in Fig. 4, approximately 1/5 of the dimension B of the conventional method using an end mill 22 with a diameter equal to the groove width of 0.6 mm.
(for example, 0.02mm).

In FIG. 8, 51 is a primary product corresponding to the above-mentioned 24, 52 is a key top surface layer (secondary molded part) corresponding to the above-mentioned surface layer 25, and the primary product 51
is molded using a primary mold into which the core 31 (or 41) described above is incorporated. The surface layer 52 is formed by molding using a conventional secondary molding die, but the resin forming the surface layer 52 hardly flows into the upper surface of the display protrusion 51a, which corresponds to the aforementioned protrusion 24a. become.

(g) Effects of the Invention As explained above, according to the present invention, an end mill selected depending on the line width of the display specified by two-color molding, the curvature of the display surface, etc. is used, and the end mill is used in the direction of the line width. Since the display protrusion forming grooves are cut by moving the protrusions, the flow of the secondary molding resin into the upper surface of the protrusions is significantly reduced or almost eliminated, and the display quality is greatly improved.

[Brief explanation of drawings]

Fig. 1 is a perspective view A showing an example of a two-color molded key top, a perspective view B showing its primary molded product, and Fig. 2 is a side sectional view showing the main structure of the primary molding die for molding the key top. Figure A is a side sectional view showing the main structure of the secondary mold. Figure 3 is a side sectional view showing a conventional method of cutting a display protrusion forming groove clearly shown on the spherical display surface into the mold. Fig. 4 is a side cross-sectional view showing a conventional method of cutting a display protrusion forming groove clearly shown on an inclined display surface into a mold; FIG. 6 is a side sectional view showing an embodiment of the present invention, FIG. 7 is a side sectional view showing another embodiment of the present invention, and FIG. FIG. 2 is a side sectional view showing a part of a two-color forming mold (key top) using the mold according to the present invention. In the figure, 2, 24, 51 are primary molded products,
2a, 24a, 51a are protrusions, 11 is a convex template,
12, 16 are concave side templates, 13, 18, 21, 3
1 and 41 are cores for cutting display protrusion forming grooves, 1
9, 22, 32 are end mills, 20, 23, 3
4 and 43 indicate display surfaces.

Claims (1)

[Claims] 1 Molding a two-color mold in which the upper surface of protrusions such as letters and symbols protruding from the surface of the mold formed in primary molding is exposed to the curved surface of a mold of a different color formed in secondary molding. In the two-color molding die, the groove of the primary molding die forming the protrusion protruding from the mold surface has a diameter smaller than the width of the protrusion such as the letter or symbol, and the groove is formed on the curved surface of the mold formed in the secondary molding. A two-color molding die characterized by being cut with an end mill that moves in three-dimensional directions.