JPH0145382B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a golf ball manufacturing method. In general, there are compression molding methods and injection molding methods for manufacturing golf balls by covering the outer periphery of the core with a cover material such as plastic. For example, to manufacture a two-piece ball by injection molding, as shown in FIG. 1, a plurality of holding pins 5 are placed inside a cavity 4 of a mold 3 consisting of an upper mold 1 and a lower mold 2, and which protrude from the upper and lower directions. The core of the golf ball 6
In this state, the cover material 8 is injected into the cavity 4 through the sprue 7, and just before the injection is completed, the pins 5 are retracted as shown in FIG. 2 to injection mold a golf ball 9. . However, such conventional injection molding methods have the following drawbacks. That is, conventionally, the golf ball 9 (finished product) was manufactured directly by injection molding, so the retraction marks of the pins 5 were directly formed on the outer circumferential surface of the golf ball 9, that is, the dimple surface. or other flat curved surfaces, therefore, conventionally, the pin 5 just before the injection is completed...
As shown in FIG. 2, the retracting movement of the pins 5 is stopped at a position where the tip surfaces of the pins 5 coincide with the inner surface of the mold 3, and the cover material 8 is further inserted into the cavity 10 created by the retracting movement. I was trying to fill it up. However, with this method, the above-mentioned cavity 1 is damaged due to distortion caused by resin flow in the cover material 8 and weld marks caused by air that has not completely escaped from inside the cavity 4.
0... The interior is not completely filled with the cover material 8, and therefore, the marks of the pins 5 appear as scratches on the outer circumferential surface of the golf ball 9, which not only lowers the product value but also prevents damage from the scratches during use. The problem is that the golf ball 9 is easily broken due to cracks, has poor durability, and has a short lifespan. The present invention solves the above-mentioned problems,
To provide a method for manufacturing a golf ball that is extremely durable and has a long life compared to conventional ones, has a beautiful appearance, and has extremely high commercial value. Therefore, a feature of the present invention is that the cover material is injected into the cavity with the core held as a core by a plurality of holding pins protruding into the cavity of the mold, and immediately before the injection is completed, the cover material is The holding pin is pulled out from the cavity to form an injection molded product, and the marks of the plurality of protruding pins on the outer peripheral surface of the molded product are removed by cutting the entire surface in post-processing. Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings. In FIG. 3, a golf ball 11 is a two-piece structure ball having a homogeneous plastic core 6 in the center, similar to the conventional example described above.
The ball 11 is constructed by covering the outer periphery of a core 6 with a plastic cover material 8 of a different type from that of the core 6, and has a large number of dimples 15 recessed throughout its outer periphery. Next, a method for manufacturing the golf ball 11 will be described. The manufacturing method includes a pre-process using an injection molding method and a post-process using a cutting method. The initial stage of the pre-process by the injection molding method is the same as in the conventional example described above. That is, in FIG. The core 6 is held as a core. As shown in FIG. 5, the inner surface 14 of the mold 3 has an uneven shape corresponding to the outer circumferential surface of the golf ball 11, and the insertion holes 1 for the holding pins 5...
3 is formed to open at a position on the inner surface 14 corresponding to the outer peripheral surface of the ball 11 other than the dimples 15 . Next, while maintaining this state, injection of the cover material 8 into the cavity 4 via the sprue 7 is started. Covering material 8 injected into cavity 4
When the amount of the cover material 8 increases and the cover material 8 reaches almost every corner of the cavity 4, and the injection of the cover material 8 is about to be completed, the core 6 held in the fixed position by the holding pins 5... Since its outer circumferential surface is supported by the cover material 8 filled in the cavity 4, holding by the holding pins 5 is no longer necessary. Therefore, at this point, while continuing the injection of the cover material 8, the holding pins 5 are pulled out from the cavity 4 by appropriate means as shown in FIG. The drawing operation is stopped at a position where the tip end surfaces of the holding pins 5 have retracted from the inner surface 14 of the mold 3 by a predetermined distance l into the insertion hole 13, as shown in FIG. Then, the cavity 12 created by the above drawing is filled with the cover material 8, and when the filling is completed, the injection of the cover material 8 is completed. After the cover material 8 in the cavity 4 is cooled and solidified, the mold 3 is opened, and a molded product 16 having an appearance as shown in FIG. 6 is completed. On the outer circumferential surface of the molded product 16, there are a plurality of pin marks 17 with a protruding size l caused by the holding pin 5 during injection molding and the contact boundary between the upper and lower molds 1 and 2 of the mold 3. A protruding parting line 18 is provided, and these are cut and removed by a cutting method in a subsequent process to complete the golf ball 11 as shown in FIG. The cutting is performed on the entire outer peripheral surface of the molded product 16 (full-surface cutting), and the cutting depth is a predetermined distance h from the outer peripheral surface of the molded product 16, as shown in FIG. Therefore, the shape and dimensions of the injection molded product 16, such as the depth dimension of the dimples 15 during injection molding, are set in consideration of the predetermined dimension h. In addition, the retraction dimension of the holding pin 5, that is, the protrusion dimension l of the pin mark 17, is also due to distortion caused by resin flow of the cover material 8 that occurs in the cavity 12 during injection molding, and failure to completely escape from the cavity 4. The weld mark (not shown) caused by air is set to be completely removed by the above-mentioned entire surface cutting. Next, the results of experiments on the appearance finish and durability of the golf ball 11 conducted with various settings for the above-mentioned predetermined dimension l are shown below. Experimental golf ball 11: (Cover material 8 was manufactured by DuPont in the US under the trade name "Surlyn 1707")
(Uses plastic sold by Surlyn 1707) Ball A (Example) - The protruding dimension l of the pin mark 17 is
0.1m/m Ball B (Example) - The protrusion dimension l of the pin mark 17 is
0.5m/m Ball C (comparative example) - protrusion dimension l of pin mark 17 is
0.65m/m Ball D (comparative example) - The protruding dimension l of the pin mark 17 is 0m/m (closest to the conventional example mentioned above) In addition, the mold used for injection molding of the above balls A, B, C and D. The shapes and dimensions of the inner surfaces 14 of No. 3 are all the same. Injection molding conditions: Heating cylinder temperature: Nozzle - 220℃ Cylinder front - 210℃ Middle - 190℃ Rear - 150℃ Cover material 8 injection pressure: 900Kg/cm ² Cutting depth dimension h: Approx. 2.5/100 ~ 5/100m /m (about 5/100 to 10/m in diameter of molded product 16)
100m/m) Durability test method: Impact is repeatedly applied to the ball 11, and evaluation is performed based on the number of impacts until the ball 11 breaks. The results of the experiment conducted under the above conditions are shown in the table below.

[Table] As is clear from the above table, in consideration of durability and appearance finish, the protruding dimension l of the pin mark 17 is approximately
It is preferable to set it to 0.1 to 0.5 m/m. Of course, when using another material as the cover material 8, the optimum value should be selected and set according to the characteristics of the material. It should be noted that the experimental results in the above-mentioned embodiments are just one example, and it goes without saying that the manufacturing conditions can be changed as long as the same effect can be obtained. The present invention has the configuration as detailed above,
The intended purpose was effectively achieved. In particular, just before the completion of injection molding, the plurality of holding pins 5 that hold the core 6 are pulled out from the cavity 4 of the mold 3, and the injection molded product 16 is
At the same time, the above-mentioned molded product 16 is obtained by the injection molding.
A plurality of pin marks 17 are molded protrudingly on the outer peripheral surface,
Since the golf ball 11 is manufactured by removing the cutting by cutting the entire surface in the post-processing, the pin marks 1 mentioned above are removed.
7. Strains and weld marks occurring in the portion 7 do not remain as scratches on the outer peripheral surface of the golf ball 11, and therefore,
It is possible to provide a golf ball that is extremely durable and has a long life without causing the problem of the ball 11 cracking due to cracking during use as in the conventional golf ball. Moreover, since the above-mentioned scars are not left and the other outer peripheral surfaces (excluding the dimples 15) are finished by cutting, it is possible to obtain a golf ball with a beautiful appearance and extremely high commercial value.

[Brief explanation of drawings]

1 and 2 are sectional views for explaining a conventional golf ball manufacturing method, and FIG. 3 is a partially sectional perspective view of a golf ball according to an embodiment of the present invention.
Figure 4 is a sectional view corresponding to Figure 2 for explaining the injection molding method, Figure 5 is an enlarged view of the main parts, and Figure 6 is a cross-sectional view corresponding to Figure 2 for explaining the injection molding method.
The figure is a perspective view of the molded product, and FIG. 7 is a partially enlarged sectional view thereof. 3... Mold, 4... Cavity, 5... Holding pin, 6
... core, 8 ... cover material, 16 ... molded product, 17 ... pin trace.

Claims (1)

[Claims] 1 Injecting the cover material 8 into the cavity 4 of the mold 3 while holding the core 6 as a core by a plurality of holding pins 5 protruding into the cavity 4,
Immediately before the injection is completed, the holding pins 5 are pulled out from the cavity 4 to form an injection molded product 16, and the plurality of pin marks 17 protruding from the outer peripheral surface of the molded product 16 are removed by cutting the entire surface in post-processing. A golf ball manufacturing method characterized by cutting and removing the golf ball.