JPH02192919A - Molding method for sphere - Google Patents

Abstract

PURPOSE:To prevent generation of defective gas accumulation by reducing dispersion of molded products and enabling uniform casting of a covering material into a cavity, by providing a covering material casting sprue at a specific angle to a mold split surface. CONSTITUTION:Spherical cores 7 are inserted as cores respectively into the central part of a plurality of spherical cavities 6 formed in a mold device to be divided into the top and bottom under a state where they are supported with a plurality of holding pins 4. Then along with injection of a covering material within the cavity 6 the holding pin 4 is pulled out through the cavity 6 prior to completion of the injection or upon the completion of the injection, the surface of the core 7 is coated with the covering material and a plurality of spheres are molded at a time. Hereupon, a covering material casting sprue 14 is provided on a split surface of a mold at an angle of at least 80 deg.. An angle of the sprue 14 to the split surface of the mold is most suitably almost perpendicular, that is, 90 deg.. Then it is preferable that resin is held under a fluid state by keeping a part or the whole of the sprue 14 warm at a temperature of at least the softening point of the resin (covering material) or heating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously molding a plurality of spherical bodies, such as two-piece golf balls, by uniformly covering the surface of a spherical core with a covering material by injection molding.

Conventionally, when manufacturing a two-piece golf ball by covering a core with a cover material by injection molding, a mold apparatus as shown in FIG. 3 has been used.

In other words, this mold packaging! ! 1 consists of an upper mold 2 and a lower mold 3, and the upper mold 2 is provided so as to be movable in the vertical direction.The mold device 1 also includes a holding pin support that supports a holding pin 4 so as to be movable in the vertical direction. 5 is provided. When manufacturing a two-piece golf ball using this mold device 1, the upper and lower molds 2.3 are closed, and the cavity 6 of the mold device 1 is closed.
The core 7 is inserted into the center of the cavity while being supported by the holding pin 4, and then the cover material is injected into the cavity 6, and the pin 4 is inserted from the cavity 6 immediately before or at the same time as the injection of the cover material is completed. is pulled out, and the core 7 is covered with a cover material.

In this case, in order to inject the cover material into the cavity 6, a sprue is provided along which dividing surface of the upper mold 2 and the lower mold 3, and the cover material is injected from this sprue and branched from the sprue into the cavity 6. It is injected. That is, in the mold apparatus 1, as described above, the holding pin 4 for supporting the core 7 and the support body 5 for supporting the holding pin 4 are provided on the upper and lower molds 2.3, and these upper and lower molds 2 and 3 are usually provided with a gas venting mechanism for venting the gas in the cavity 6, although not shown in the drawings.For this reason, the thickness of the upper and lower molds 2.3 is usually formed to be about 150 to 200I,
The thickness of the mold device is thick. Therefore, in order to shorten the sprue distance and facilitate the release of the sprue after opening the mold, the cover material injection sprue is formed along the mold parting surface, for example, as shown in Fig. 4.5. Runners 9 are branched from 8 in an H-shape or X-shape along the dividing plane, and each runner 9 forms cavities 6a, 6b.

A method of injecting a cover material into 6c and 6d is usually adopted.

However, if the sprue 8 and the runner 9 are placed on the same surface, the cavities 6a and 6b shown in FIGS. 4 and 5 will have a larger amount of resin than the cavities 6c and 6d. Moreover, the timing is also faster.

For this reason, there is a problem in that there is a difference in the filling state between the cavities 6a, 6b, 6c, and 6d, and a difference in quality between the molded products.

In addition, the injection of the cover material into the cavity 6 in the two-piece golf ball mold apparatus generally employs a ring runner 10 method, as shown in FIG. The structure is such that the resin is simultaneously injected into the cavity 6 from several gates 11 formed by As a result, the core of the core is eccentric toward the side where the flow rate is low, making the thickness of the cover material uneven, and the gathering point of the resin flowing from the gate is at the top of the cavity. It may shift from the hole and cause gas venting failure.

Conventionally, in order to prevent these, a throttle 13 is provided in the middle of the runner 9 that supplies resin to the ring runner 10, as shown in FIG. The amount of inflow between the gates 11 of 6 is adjusted. In this case, the above-mentioned flow rate balance and gate inflow amount are adjusted by cutting the throttle or gate to an appropriate width.

However, these operations not only require great skill but are also time consuming, and the gate thickness becomes non-uniform, resulting in a significant drop in work efficiency in the finishing process after molding.

The present invention has been developed in view of the above circumstances, and allows the flow to flow into each cavity without the need for difficult adjustment of the runner diaphragm or gate of the mold when a large number of spheres such as two-piece golf balls are produced by injection molding. It is possible to make the amount of resin uniform, and it is possible to reduce variations in each molded product as much as possible when molding multiple pieces, and it is also possible to make the amount of resin flowing into the cavity from each gate as uniform as possible, and to prevent unevenness of the core. It is an object of the present invention to provide a method for forming a sphere, which can uniformly cover a cover material by preventing cores, prevent degassing failures, and facilitate crisp finishing.

In order to achieve the above object, the present invention includes a plurality of spherical cavities formed in a mold device that is divided into upper and lower parts, each having a spherical core as a core supported by a plurality of holding pins at the center of each of the plurality of spherical cavities. In the method of molding a plurality of spheres at the same time by inserting the core into the core, injecting the cover material into the cavity, pulling out the holding pin from the cavity immediately before or at the same time as the injection is completed, and covering the core surface with the cover material. , the cover material injection sprue is provided at an angle of 80' or more with respect to the mold dividing surface.

Here, the more preferable angle of the sprue with respect to the mold dividing plane is 85'', and the optimal angle is approximately perpendicular (90°). It is preferable to keep the resin in a fluid state by keeping it warm or heating it above.

In addition, the end of the sprue that reaches the mold dividing surface is
A plurality of runners can be connected along the dividing plane in an H-shape, an X-shape, etc. similar to the conventional one, and the cover material can be injected into the cavity from the ring runner through the gate.

Kei-■ According to the present invention, the cover material can be uniformly injected into the cavity by providing the cover material injection sprue at an angle of 80 degrees or more with respect to the mold dividing surface.

That is, in general, the flow velocity distribution when resin is flowing through a runner is as shown in Figure 7 (a), where the flow velocity is maximum at the center of the runner and is symmetrical, and the flow velocity decreases as it approaches the runner wall. , the flow velocity becomes zero at the wall surface. In addition, the resin temperature distribution in this case is as shown in FIG. 7(b),
The area with a large flow velocity gradient (near the runner wall) has a large shear force, so the temperature is higher than the center of the runner, and a temperature peak occurs. When this flow is divided into left and right halves, as shown in FIG. 8, the temperature distribution becomes asymmetrical with respect to the center line of the runner after branching. If the resin with this left-right asymmetrical temperature distribution is further divided into two, the resin temperatures of the left and right branches will be different, and more resin will flow toward the runner on the higher resin temperature side, resulting in an overall gap between the cavities. The balance will be lost. Therefore, if the two-split branching is performed more than once in the same plane, the balance of resin inflow into the cavity cannot be maintained. With the conventional configuration in which resin is injected into the cavity, it is difficult to completely balance the injection of resin into the cavity except for one injection.

In contrast, in the present invention, a sprue is provided at an angle of 80" or more, preferably approximately perpendicularly, to the mold dividing surface, and resin is injected from the sprue, and the resin is injected into each runner at the mold dividing surface. Can be evenly branched.

Therefore, according to the present invention, since the sprue for injecting the cover material at a predetermined angle is provided on the mold dividing surface, the drawing of the runner is uniform for each runner leading to a plurality of cavities without having to adjust it in post-processing. Since the resin can be poured into each cavity and the resin can be uniformly filled into each cavity, it is possible to reduce variations in quality between multiple molded products as much as possible. In order to prevent as much as possible the difference in flow between the left and right sides caused by the difference in resin temperature when branching left and right at the entrance of the gate, and to reduce the difference in flow between the gates as much as possible, It is possible to prevent eccentricity of the core and uniformly cover the core with the cover material without adjusting the gate of the mold in post-processing, and gas venting can prevent the occurrence of defects.

In addition, part or all of the sprue is heated or kept warm,
By keeping the cover material inside the sprue above the resin softening point, it can be
Even if various devices are built in and the mold device becomes thick, it will not be difficult to release the sprue and the molding workability will not be impaired. Next, Figures 1 and 2 are shown. The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

FIG. 1 shows an example of a mold apparatus used for carrying out the present invention. Components that are the same as those of the mold apparatus described in FIG. 3 above are given the same reference numerals, and their explanations will be omitted.

In the mold apparatus shown in FIG.
A heating device (heater) 17 is provided around the sprue 14, passing through the center of the sprue 6 and extending along the mounting direction relative to the mold dividing surface (lower surface of the base 16 of the upper mold 2). Thus, the temperature of the resin (covering material) passing through the sprue 14 is always heated above its softening point.

At the lower end of this sprue 14, as shown in FIG. 2, runners 9 are formed radially along the mold dividing surface.
The tip of each runner is connected to the ring runner 10 as shown in FIG.
has been contacted.

Here, on the lower surface of the base 16 of the upper mold 2 and the upper surface of the base 18 of the lower mold 3, the runner 9 and the ring runner 1o are provided.
A groove corresponding to the cavity 6 is formed, and a hemispherical recess corresponding to the cavity 6 is formed, and when the upper mold 2 and the lower mold 3 are closed and brought together, the runner 9, the ring runner 10, and the cavity 6 are formed. It is something that will be done.

When manufacturing a sphere using the above mold, first the spherical core 7 is
is inserted into each cavity 6, the mold is closed, and the core 7 is placed in the center of the cavity 6 using the holding pin 4. After that, the molten resin (cover material) is applied with pressure from the outside and is poured into the injection port 1 of the sprue.
Inject from 9. The molten resin then passes through sprue 14 and into radial runners arranged perpendicularly thereto, where each runner is evenly branched with resin. The resin that has passed through the runner is branched left and right by the ring runner, and then filled into the cavity through the gate. In addition,
The other methods are the same as the conventional method.

In this case, the molten resin is injected from the sprue 14 into the runner 9 arranged perpendicularly thereto and branches radially, so there is no asymmetric temperature distribution in the cross section within the runner as shown in FIG. . Therefore, even when the resin passes through the runner and branches to the left and right in the ring runner population, there is almost no difference in temperature between the left and right resin, and therefore the resin flows evenly to the left and right of the ring runner. As a result, the flow passing through the gate becomes even, the core of the core is less likely to be eccentric, and the convergence position of the resin within the cavity does not deviate from the gas vent hole, reducing the rate of gas vent defects. Can be reduced.

Therefore, since the above method essentially does not produce a difference in the flow rate between the branches from the sprue to each runner and the ring runner branch, it is difficult to draw and gate the runners of the mold, and it requires a lot of skill. Almost no adjustment is required.

Furthermore, when the molded product is removed from the mold after molding is completed, the sprue is heated above the resin softening point of the cover material, and the molten resin does not harden within the sprue, so the molding work is not damaged.

In the above embodiment, the runners are arranged radially, but other arrangements may be used, for example, an H-shaped arrangement as shown in FIG. 4 may be used.

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

[Experiment example]

Using a mold apparatus as shown in Fig. 1, a sprue arranged perpendicular to the mold parting plane is heated, and the sprue shown in Fig. 9 (
A two-piece golf ball was prepared by injection molding a cover material onto the surface of a spherical core with two types of runner arrangements, a) and (b), and the resin injection balance between cavities and gates and molding defects were investigated.

For comparison, molding was carried out in the same manner using a conventionally used mold in which a sprue was provided along the dividing surface of the mold (FIG. 9(C)).

In this case, tests were conducted before and after runner throttling and gate adjustment.

Table 1 shows the sprue position, runner arrangement, presence or absence of sprue heating, and the temperature of the above mold.

The common molding conditions are as follows.

Molding conditions Ring runner diameter 60nn Injection temperature 220℃ Injection pressure setting 120kg/aJ Holding pressure setting 60kg/cJ Injection time
3.5 seconds Holding pin withdrawal timing When injection is completed Mold cooling temperature 20℃ Ejector stroke 10n11 Under the above molding conditions, the defect rate for each mold's cavity inflow difference, thickness unevenness, and gas vent is as follows. was measured.

The cavity was molded without the core of the core, and the weight of each of the four balls was measured, and the difference between the maximum weight and the minimum weight was determined. This is an index showing the balance between each cavity.

The difference between the maximum and minimum cover thickness of the hemoglottically molded ball was measured. This is an indicator of the gate balance of one cavity because if there is a difference in the amount of resin flowing from each gate of one cavity, the core will be eccentric and the thickness of the cover will vary.

As shown in FIG. 10, gas retention 21 occurs between the core 7 and the cover material 20 covering the core 7,
As shown in the figure, the rate at which flow marks 23 were generated on the surface of the sphere 22 was measured. This occurs because if there is a difference in the amount of resin flowing in from the gates, the collection point of the resin from each gate is shifted from the gas vent hole at the apex of the cavity.

The results are also listed in Table 1.

As explained above, according to the method for manufacturing spheres according to the present invention, when a thick mold device is used to perform multi-cavity molding, the mold runners and Even without adjusting the flow of the gate, the core can be uniformly coated with the cover material, thereby reducing variations in the molded product and preventing the occurrence of gas retention defects.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an example of a mold device used for carrying out the present invention, FIG. 2 is a layout diagram of the runner and cavity of the mold device shown in FIG. 1, and FIG. 3 is a diagram of a conventional mold device. A schematic side view, FIGS. 4 and 5 are layout diagrams of the runner and cavity of a conventional mold in which resin is injected from the mold dividing surface, respectively. FIG. 6 is a sectional view showing the ring runner, and FIG. 7 is a schematic side view. The figure is a graph showing the flow velocity and temperature distribution of the resin in the runner in the cross section of the runner. Figure 8 is a graph showing that the resin temperature distribution after branching of the runner becomes asymmetric within the runner. Figure 9 is used in the experiment. FIG. 10 is a cross-sectional view showing the occurrence of gas retention, and FIG. 11 is a front view of the sphere showing the occurrence of uneven flow. 1... Mold device 3... Lower Mold 6... Cavity 9... Runner 11... Gate 2... Upper Mold 4... Holding pin 7... Spherical core 10... Ring Runner 14...Sprue Applicant Brideston Co., Ltd. Agent Patent Attorney Takashi Kojima I1-゛Wall. Ran r- Kirisabaku 1 Slimming Bird Bokuzono Lunch-Example I Dye Figure 9

Claims (1)

[Claims] 1. Insert a spherical core as a core into the center of multiple spherical cavities formed in a mold device that is divided into upper and lower parts, supported by multiple holding pins, and inject the cover material into the cavities. At the same time, in the method of simultaneously molding a plurality of spheres by pulling out the holding pin from the cavity immediately before or at the same time as the injection is completed, and covering the core surface with the cover material, the cover material injection sprue is placed at an angle of 80° against the mold dividing surface. A method for forming a sphere, characterized by forming the sphere at an angle of more than °.