JPH05200914A - Sphere and its production - Google Patents

Abstract

PURPOSE:To easily produce a sphere high in sphericity without deviation of a core at low cost by holding a supporter in a mold and performing the positioning of the core when the supporter is enveloped by a second resin layer. CONSTITUTION:A sphere is constituted of a spherical core 2, a first resin layer 3 with which at least one part of the spherical core is covered, a second resin layer 5 for enveloping the core 2 and the first resin layer 3 and a pair of supporters 4 described below. The supporters 4 are integrally molded together with the first resin layer 3 and projected. Further when the supporters 4 are enveloped by the second resin layer 5, these are held in a mold to perform positioning of the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small spherical body having a high sphericity used for a signal input device and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a trackball device or a mouse device is used as a signal input device for a peripheral device of a computer, and a spherical ball having a high sphericity is used for these signal input devices. This ball is a highly precise product having a high sphericity and an extremely smooth surface, and is required to have a certain weight.

[0003]

By the way, as this type of ball, a resin ball having a steel ball or the like as a core and a surface coated with a colored resin is used in order to give a certain weight. However, in order to uniformly coat the surface of the steel ball with a resin, without deviation of the steel ball, and to manufacture with high sphericity, an expensive manufacturing apparatus accompanied by a highly accurate control device is required, Inevitably an expensive ball. In addition, this type of ball is required to have a beautiful appearance,
It is also necessary to prevent the occurrence of color unevenness that can be visually confirmed, which is an inconvenience that the ball becomes more expensive.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a sphere and a method for producing the sphere, which have a high sphericity and a beautiful appearance without any deviation of the core, which is simple and inexpensive to produce. To provide.

[0005]

In order to achieve the above-mentioned object of the present invention, a first aspect of the present invention is to provide a spherical core, a first resin layer at least partially covering the core, the core, and A second resin layer having a spherical outer surface that wraps the first resin layer, is integrally molded with the first resin layer and projects outward, and when the second resin layer is wrapped with the second resin layer, A pillar for positioning the core in cooperation with a molding die,
The strut is characterized in that a portion exposed from the second resin layer is removed when the second resin layer is spherically processed. Further, the invention according to claim 2 is a primary molding step of resin-molding a first resin layer that at least partially covers the spherical core, and a pillar that extends outward from the first resin layer. And a second molding step of wrapping the core and the first resin layer with a second resin layer in a state where the pillar is held in a mold and the core is positioned in the mold, and exposed from the second resin layer. And a spherical surface processing step of removing the pillars and polishing the outer surface of the second resin layer into a spherical shape.

[0006]

According to the above-mentioned means, the pillar for positioning the core in cooperation with the mold for molding the second resin layer when wrapped with the second resin layer is integrally molded with the first resin layer, and the pillar by the pillar is formed. By positioning the second resin layer accurately and uniformly coating the surface of the core with the second resin layer, it is possible to obtain a sphere having a high sphericity with no deviation of the core by a simple manufacturing method.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described in detail based on. Here, FIG. 1 is a sectional view of a main part of a sphere according to the present invention, FIGS. 2 to 10 are process diagrams of a method for manufacturing a sphere according to the present invention, and FIG. Lower mold cross-sectional view, FIG. 3 is a cross-sectional view of the upper and lower molds in a clamped state in the primary molding process, and FIG. 4 is a perspective view of the primary molded product.
5 is a sectional view of the lower mold on which the primary molded product of the secondary molding process is placed, FIG. 6 is a sectional view taken along line AA in FIG. 5, and FIG. 7 is a sectional view of the upper and lower molds in the mold clamping state in the secondary molding process. FIG. 8 is a side sectional view of the secondary molded product, FIG. 9 is a plan sectional view of the secondary molded product, and FIG. 10 is a sectional view of the elemental ball taken along line BB in FIG.

The sphere 1 according to the present invention has a steel ball 2 having a diameter of about 12 mm as a center core, and the steel ball 2 has a large specific gravity and has a desired weight as the sphere 1. The steel ball 2 is covered with a thermoplastic first resin layer 3 made of polybutylene terephthalate or the like on a part of the surface thereof in a belt shape, and the steel ball 2 extends outward from the steel ball 2 from the first resin layer 3. It has a pair of protruding columns 4. The pillar 4 serves as a support member for positioning the steel ball 2 at the center of the spherical body 1 in the mold for molding the second resin layer 5 in the secondary molding step described later, and in the primary molding step described later, First resin layer 3
It is molded at the same time. The first resin layer 3 may cover the entire steel ball 2. In addition, the entire surface of the spherical body 1 is covered with the second resin layer 5 that encloses the steel ball 2, the first resin layer 3 and the support column 4, and the surface of the second resin layer 5 is smooth by polishing and the appearance is beautiful. Is becoming The sphere 1 having such a structure has an appropriate weight due to the steel ball 2, and has a smooth surface and no deviation of the core and excellent sphericity. It can be used for a ball device or a ball such as a mouse.

Next, a method of manufacturing the sphere 1 will be described with reference to FIGS. First, as shown in FIG. 2, the steel ball 2 is placed in the central recess 8a of the cavity of the primary forming lower die 8. The lower mold 8 is provided with recesses 8b, 8c, and 8d filled with resin for forming a post 4, a positioning boss 9, and a first resin layer 3 which will be described later, and directly below the central recess 8a. Vertically movable pin 1
Two are provided. After the steel ball 2 is placed on the lower die 8, the upper die 10 for primary molding is placed on the lower die 8 and clamped as shown in FIG. The upper mold 10 includes the recesses 8a, 8b, 8 of the lower mold 8.
recesses 10a, 10b, 1 having the same shape at positions facing d
0d is formed. Then, the recesses 8a, 8b, 8c, 8d and the recesses 10 of the upper and lower molds 8 and 10 that have been clamped.
The molten resin is filled from a gate 11 into a, 10b, and 10d. After a predetermined resin solidification time has passed, the upper mold 10 is moved and the pins 12 of the lower mold 8 are moved upward to take out the primary molded product 13 shown in FIG. Ends. The primary molded product 13 includes a first resin layer 3 that surrounds the surface of the steel ball 2 in a strip shape, and columns 4 that project from both side surfaces of the first resin layer 3.
And a positioning boss 9 and the like at the tip of the column 4. Next, as shown in FIGS. 5 and 6, the primary molded product 13 is positioned at the center of the lower mold 15 by inserting the positioning boss 9 into the hole 15a of the lower secondary mold 15. By this positioning,
Since the steel ball 2 is located at the center of the sphere 1 and the steel ball 2 is not offset, the rotation of the sphere 1 becomes smooth and the sphericity can be increased. A hemispherical recess 15b which becomes the second resin layer 5 is formed in the center of the lower mold 15, and the hemispherical ring-shaped recess 15c and the recess 15c are electrically connected to the gate 16 outside the recess 15b. A plurality of recesses 15d are formed. Two vertically movable pins 18 are disposed directly below the recess 15c. After the primary molded product 13 is placed on the lower mold 15, the upper mold 17 for secondary molding is placed on the lower mold 15 and clamped. The upper mold 17 includes the recesses 15b, 15 of the lower mold 15.
recesses 17b, 1 having the same shape at positions facing c, 15d
7c and 17d are formed. After mold clamping, recess 15
The molten resin is filled in the recesses 15b, 15c, 15d and the recesses 17b, 17c, 17d of the upper and lower molds 15, 17 with the c, 15d and the recesses 17c, 17d as the gate 16 and the state shown in FIG. 7 is obtained. Since the gate 16 is composed of the ring-shaped recesses 15c and 17c and the plurality of recesses 15c and 17c, the molten resin uniformly flows into the hemispherical recesses 15b and 17b, so that the solidification time can be equalized. Therefore, the occurrence of color unevenness or the like of the second resin layer 5 is prevented. After a predetermined resin solidification time has passed, the upper mold 17 is moved and the pin 18 of the lower mold 15 is moved upward to move the secondary molded product 19 shown in FIGS.
Is taken out, and the manufacturing process of the secondary molded product is completed. The secondary molded product 19 has a second resin layer 5 that surrounds the first resin layer 3, and a pillar 4, a positioning boss 9, and a gate filling portion 20 are formed around the second resin layer 5. Then, the gate filling portion 20 is sequentially cut and removed to form a base ball 21 in which the surface of the steel ball 2 shown in FIG. 10 is covered with the second resin layer 5. Next, the base balls 21 are subjected to a plurality of barrel polishing steps in which the size of the abrasive grains is changed, and the surface layer 5a of the second resin layer 5, a part of the pillars 4, and the rest of the gate filling portions 20a, 20b ... 20f. Are removed, and the final sphere 1 in FIG. 1 is completed.

Although the illustrated embodiment has been described above, the present invention is not limited to the embodiment of the above embodiment,
Various changes can be made to the components. For example, when it is necessary to make the sphere 1 smaller and heavier, the material of the core can be changed to a material having a larger specific gravity than the steel ball, and the material of the core can be changed according to the demand.

[0011]

As is apparent from the above description, according to the first aspect of the invention, the spherical core is wrapped with the first and second resin layers and is integrally molded with the first resin layer. By having a pillar that determines the core in cooperation with the mold for molding the resin layer, the sphere has a high degree of sphericity and a beautiful appearance, and the manufacturing is simple and inexpensive. According to the invention as set forth in claim 2, a primary molding step of covering at least a part of the core with the first resin layer having integrally formed columns, and positioning the core and the first resin layer in the mold by the columns. By having a secondary molding step of wrapping with the second resin layer and a spherical surface processing step of removing the pillars exposed from the second resin layer and polishing the outer surface of the second resin layer into a spherical shape, the manufacturing is simple. It is possible to obtain an inexpensive one having a high sphericity with no deviation of the core.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a spherical body showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a lower die on which a steel ball is placed in a primary forming step showing an embodiment of the present invention.

FIG. 3 is a sectional view of the upper and lower molds in a clamped state in a primary molding process.

FIG. 4 is a perspective view of a primary molded product.

FIG. 5 is a cross-sectional view of a lower mold on which a primary molded product of a secondary molding process is placed.

6 is a cross-sectional view taken along the line AA in FIG.

FIG. 7 is a cross-sectional view of the upper and lower molds in a clamped state in a secondary molding process.

FIG. 8 is a side sectional view of the secondary molded product.

FIG. 9 is a plan sectional view of a secondary molded product.

10 is a cross-sectional view of the element ball taken along line BB in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 sphere 2 steel ball 3 first resin layer 4 support 5 second resin layer 8 lower mold for primary molding 9 positioning boss 10 upper mold for primary molding 13 primary molded product 15 lower mold for secondary molding 17 upper mold for secondary molding 19 Secondary molded product 20 Gate filling part 21 Elementary ball

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G06F 3/033 340 A 7927-5B Z 7927-5B // B29L 9:00 4F 31:34 4F 31:54 4F (72) Inventor Atsushi Nakano 1-7 Yukiya Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd.

Claims (2)

[Claims] 1. A spherical core, a first resin layer that at least partially covers the core, a second resin layer that surrounds the core and the first resin layer and has a spherical outer surface, and the first resin. A pillar that is integrally molded with the layer and protrudes outwardly, and cooperates with a mold that molds the second resin layer when wrapped with the second resin layer to position the core. A sphere, wherein a portion exposed from the second resin layer is removed during spherical surface processing of the second resin layer. 2. A primary molding step of resin-molding a first resin layer that at least partially covers a spherical core, and a pillar projecting outward from the first resin layer, and the pillar. A secondary molding step of wrapping the core and the first resin layer with a second resin layer in a state where the core is positioned in the mold while being held in a mold, and removing the pillars exposed from the second resin layer, And a spherical surface processing step of polishing the outer surface of the second resin layer into a spherical shape.