JPH0729388B2 - Golf ball manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a golf ball such as a two-piece golf ball by an injection molding method. More specifically, a gas pool is generated between the core and the cover. The present invention relates to a method for manufacturing a golf ball, which is capable of satisfactorily preventing this.

2. Description of the Related Art Conventionally, as a method for manufacturing a two-piece golf ball by an injection molding method, as shown in FIGS. 5 and 6, for example, a cavity 2 is formed in a cover molding mold 1 including an upper mold 1a and a lower mold 1b. The core 3 of the two-piece golf ball is inserted as a core, and the core 3 is supported by a plurality of holding pins 4 (upper and lower four in this example), and then the molding material 5 for the cover is injected into the cavity 2. At the same time as the injection of the cover material 5 is completed or at the same time as the injection is completed, the holding pin 4 is pulled out from the cover material 5,
A method of covering the core 3 with a cover having a large number of dimples is generally adopted.

In this case, the injected cover material resin 5 flows into the space between the core 3 and the peripheral wall of the cavity 2, and the flow of this resin normally converges at the deepest point of the cavity 2,
As a result, the entire surface of the core 3 is covered with the cover material resin 5. For this reason, in the conventional injection molding apparatus, substantially cylindrical degassing holes 6 are formed at the deepest locations of the cavities 2 of the lower mold 1b and the upper mold 1a, which are the convergence positions of the flow of the cover material resin 5. A substantially cylindrical fixing pin 7 having a diameter slightly shorter than the inner diameter of the hole 6 is inserted and fixed in the gas vent hole 6 to remove air generated in the cavity 2 or the cover material resin 5 from the gas vent hole 6 It escapes to the outside through the gap 8 between the pin 7 and the pin 7.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional injection molding method, a gas pool is likely to occur between the core 3 and the cover. That is, as described above, the flow of the cover material resin 5 injected into the cavity 2 normally converges at the deepest portion of the cavity, but the flow of the resin 5 at this time is as shown in FIG.
Since the intermediate portion 9 between the core 3 and the core 3 is the fastest, the gas 10 remains inside the resin 5 as shown in FIG. 5
Since the gas is blocked, the gas 10 remaining in the resin 5 is not satisfactorily discharged from the gas vent hole 6, resulting in a gas pool 11 between the core 3 and the cover 5 as shown in FIG. It is a thing.

When the gas pool 11 is generated as described above, the strength of this portion is insufficient, and not only the durability of the golf ball is deteriorated,
When the ball is taken out of the mold 1, the cover material 5 is lifted by the pressure of the gas pool and the ball is deformed. Actually, the rate of defective molding in golf ball production is 3 to 30% even for a proficient manufacturer, but 90% or more of defective molding is caused by the generation of the gas pool.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a golf ball, which can prevent gas accumulation from occurring between the core and the cover and can effectively suppress the generation of defective molding products. The purpose is to

Means for Solving the Problems In order to achieve the above object, the present invention supports a core inserted in a mold cavity as a core with a plurality of holding pins, and injects a cover molding material into the cavity. In a method for producing a golf ball in which the holding pin is pulled out from the cover material and the core is covered with the cover immediately before or at the same time as the injection of the cover material is completed, the mold is formed on the mold at a convergent position of the flow of the cover molding material. In addition to forming a gas vent hole in the cavity, insert the gas vent pin into the gas vent hole so that the gas vent pin can advance and retreat, and place the tip of the gas vent pin in contact with or close to the core A structure for injecting the cover molding material into the container and pulling out the gas releasing pin from the cover material immediately before or at the same time as the completion of the injection of the cover material. It was done.

In the manufacturing method of the present invention, the gas vent pin is inserted into the gas vent hole so that the gas vent pin can advance and retreat, and the cover material resin is injected into the cavity while the tip of the gas vent pin is in contact with or close to the core. Therefore, when the flow of the resin converges, the tip of the gas releasing pin is inserted into the gas remaining inside the resin. Therefore, by pulling out this pin from the resin, communicating the above-mentioned residual gas with the outside, and letting the resin flow into the cavity after pulling out the pin, the cover is attached to the core without leaving a gas reservoir between the core and the cover. It can be coated.

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

Example FIG. 1 shows an example of an injection molding apparatus used for carrying out the present invention. In FIG. 1, the same components as those of the apparatus of FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In this device, a columnar gas vent hole 12 is formed at the deepest point of the cavity 2 of the lower mold 1b and the upper mold 1a, which is the converging position of the flow of the cover material resin, and the gas vent hole is formed. Gas vent pins 13 each having a diameter slightly shorter than the inner diameter of the hole 12 are inserted in the hole 12 so as to be able to advance and retreat. The pins 13 advance into the cavity 2 through the hole 12 and retreat from the cavity 2 into the hole 12. It's ready to go.

When manufacturing a golf ball with the above apparatus, first
As shown in the figure, after the core 3 is supported by the holding pins 4 and the degassing pins 13, the cover material resin 5 is injected into the cavity 2. Then, since the gas vent pin 13 is present at the position where the flow of the cover material resin 5 converges, the resin 5 converges around the gas vent pin 13 and the gas remaining inside the resin 5 as shown in FIG. The tip of pin 13 is inserted into pin 10. Then, when the injection of the resin 5 is completed and the pin 13 is pulled out from the resin to the inner surface of the cavity, the gas 10 remaining inside communicates with the outside and a sufficient injection pressure is applied to the resin. Because of pin 13
The action works to fill the space after pulling out. At this time, the surface of the mold 1 is usually cooled to 5 to 20 ° C, and the core 3
Since the temperature is lower, the core 3 is better than the resin near the mold 1.
The resin in the vicinity has a higher fluidity, and as a result, as shown in FIG. 4, it flows so as to fill the space after the pin 13 is pulled out from the portion near the resin core 3, and as a result, the resin itself releases the gas vent hole.
With 12, the gas can be completely discharged from the cavity 2 without blocking.

In this case, in the present invention, the diameter of the degassing pin 13 is preferably formed to be slightly smaller than the inner diameter of the degassing hole 12, so that when the pin 13 is inserted in the cover material resin and when the pin 13 is Satisfactory degassing is performed in any case where the cover material is extracted from the resin. Also,
It is preferable that the timing of pulling out the pin 13 be the same as the completion of the injection, whereby the gas remaining between the cover material resin and the core can be reliably removed.

In the above embodiment, the core was supported by the gas releasing pin 13, and the tip of the pin 13 was brought into contact with the core.
The tip of the pin 13 does not necessarily have to be brought into contact with the core, and may be brought close to the core.

Next, the effects of the present invention will be specifically shown by experimental examples.

Experimental Example A golf ball was manufactured by the method described above using the apparatus shown in FIG. 1 (example of the present invention). For comparison, a golf ball was manufactured by the device shown in FIG. 5 (comparative example).

Table 1 shows the gas pool defect rate and the burr state of the gas vent holes at this time. The clearance between the air bleeding hole and the pin and the quantity to be implemented are as shown in Table 1.

From the results in Table 1, it is recognized that the method of the present invention can favorably suppress the generation of gas pools. In particular, the present invention example
Even if the gap between the gas vent holes is made small as in Nos. 1 and 2, not only the defective rate of gas accumulation is reduced, but also molding without burrs is made possible and post-treatment of the ball surface is not required. On the other hand, it was confirmed that the conventional method is likely to cause gas accumulation. In particular, in Comparative Example 3, the gap between the gas vent holes is too large, and the resin flows deep into the gap, so that the resin that has flowed in is left behind at the time of mold release, and therefore the gap is rather filled in continuous molding, which is a defect. The rate was increasing.

Effects of the Invention As described above, according to the method for manufacturing a golf ball of the present invention, it is possible to satisfactorily prevent gas accumulation from occurring between the core and the cover, and to minimize the incidence of molding defects. Can be reduced to.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an injection molding apparatus used for carrying out the present invention, FIGS. 2 to 4 are schematic cross-sectional views showing the flow of a cover material resin in the apparatus, and FIG. FIG. 6 is a schematic sectional view showing an example of a golf ball injection molding apparatus, FIG. 6 is a plan view showing a lower mold of the apparatus, FIG.
FIG. 9 to FIG. 9 are schematic cross-sectional views showing the flow of the cover material resin in the same apparatus. 1 ... Mold, 2 ... Cavity, 3 ... Core, 4 ... Holding pin, 5 ... Cover material, 11 ... Gas reservoir, 12 ... Gas vent hole, 13 ... Gas vent pin.

Claims (1)

[Claims] 1. A core inserted into a mold cavity is supported by a plurality of holding pins as a core, and a cover molding material is injected into the cavity, and a cover material is injected immediately before or simultaneously with the completion of injection of the cover material. In the method of manufacturing a golf ball in which the holding pin is pulled out from the core and the core is covered with a cover, a gas vent hole is formed in the mold at the convergence point of the flow of the cover molding material, and the gas is discharged. Insert the gas vent pin into the vent hole so that it can move back and forth, and inject the cover molding material into the cavity with the tip of the gas vent pin in contact with or close to the core, and complete the injection of this cover material. A method of manufacturing a golf ball, characterized in that the degassing pin is pulled out from the cover material immediately before or at the time of completion of injection.