JPH08300403A - Injection molding method of golf ball and mold therefor - Google Patents

Abstract

PURPOSE: To easily and assuredly discharge air in a cavity of a mold so as to prevent generation of flashes by forming vent holes which communicate with the cavity in the mold and movably arranging, in the holes, movable pins whose head ends are formed into shapes capable of blocking openings at the cavity side of the holes. CONSTITUTION: In between holding pins 4 of an upper mold 1a and a lower mold 1b, vent holes 11 are formed in an arrangement opposed to each other. Each vent hole 11 is formed such that an opening 12 communicating with a cavity 2 has a small cylindrical shape 13 and a side which opens to the outside has a large cylindrical shape 14. In the holes 11, movable pins 15 are arranged movably. The cavity 2 is filled with a molding material. Immediately before the material enters the holes 11, moving devices 18 actuate the pins 15 to move toward the cavity 2 by a signal from a control device 19. Head ends of small cylindrical sections 16 of the pins 15 proceed in between the ends of the openings so as to block the openings 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball injection molding method and an injection molding die used therefor, and is particularly suitable for injection molding a golf ball cover.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a method of manufacturing a two-piece golf ball by injection molding, for example, as shown in FIG. 6, a core 3 of a two-piece golf ball is placed inside a cavity 2 of a cover molding mold 1 composed of an upper mold 1a and a lower mold 1b. The core 3 is inserted as a child, further, the core 3 is supported by a plurality of holding pins 4 (upper and lower four in this example), and then a molding material (cover material) 5 for the cover is injected into the cavity 2 and A method of covering the core 3 with a cover having a large number of dimples is generally adopted by pulling out the holding pin 4 from the cover material 5 immediately before or at the same time as the injection of the cover material 5 is completed.

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, whereby the core 3 The entire surface of the above is covered with the cover material resin 5. Therefore, in the conventional injection molding apparatus, substantially cylindrical degassing holes 6 are formed at the deepest points 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. At the same time, 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 releasing hole 6, and the air in the cavity 2 is injected with the injection pressure to form the gas releasing hole 6 and the pin 7. It escapes to the outside through the gap 8 between them. Further, in this case, air is also discharged from the gap 10 between the inner peripheral surface of the insertion hole 9 for the holding pin 4 and the holding pin 4.

However, the gaps 8 and 10 are usually 2
/ 100 to 4/100 mm, and if it is more than 100 mm, the resin 5 is inserted into these gaps 8 and 10, causing a problem of burrs. For this reason, since the gaps 8 and 10 have to be formed in such a narrow manner, it is difficult to discharge air, and weld defects and air entry defects are likely to occur in the molded product. Further, since it is difficult to discharge air, it is necessary to increase the injection pressure, which easily causes burrs and requires a large mold clamping force. Further, if the injection speed is increased, the air will not escape completely, and welds and air-entry defects will easily occur, making it difficult to mold the cover thinly. For example, it was difficult to mold the cover twice.

A method is also known in the prior art in which a gas vent pin is projected and retracted in the cavity to vent gas (Japanese Patent Laid-Open No. 63-45040), but this method also allows
The gap between the degassing pin and the degassing hole is also 5 to 30.
The gap is about μm, and the gap is as narrow as the above.

The present invention has been made in view of the above circumstances.
An injection molding method for a golf ball, which can easily and surely discharge the air in the mold cavity, and which can prevent injection of air, weld defects, and burrs as much as possible to inject a golf ball, and An object is to provide a mold for injection molding.

[0007]

In order to achieve the above object, the present invention provides (1) a method of injection molding a golf ball by introducing a molten injection molding material for a golf ball into a cavity of a mold. In the above step, a gas vent hole communicating with the cavity is formed in the mold, and a movable pin having a tip portion capable of closing the cavity side opening of the hole is movably arranged in the hole. In this state, the molten molding material is injected and introduced into the cavity with the tip of the pin not blocking the opening, and the air in the cavity is discharged from the hole and introduced into the cavity. (2) A golf ball injection molding method, characterized in that the pin is moved to close the opening with the tip of the pin immediately before the molten molding material enters the hole. A golf ball injection molding die having an upper die and a lower die, and forming a hollow spherical cavity inside by joining the upper die and the lower die in a separable manner, one of the upper die and the lower die, or A gas vent hole communicating with the cavity is formed on both sides, and in this hole, a movable pin having a tip portion capable of closing the cavity side opening of the hole is movably disposed. A mold for injection molding a golf ball, characterized in that the opening can be opened and closed by the movement of the movable pin. In this case, the distal end surface of the movable pin is formed into a hemispherical convex shape capable of forming a dimple of a golf ball or a concave shape capable of forming a land portion of a golf ball, and when the distal end portion of the pin closes the opening, It is preferable to form a part of the mold cavity surface with the tip end surface to obtain a golf ball having a surface portion corresponding to the tip end surface of the pin.

Here, the movement of the movable pin toward the opening portion is started when the injection amount of the molding material by the injection molding machine reaches a predetermined value, or the movement of the movable pin toward the opening portion is started. The movement of the air can be started when the pressure of the air discharged from the cavity to the gas vent hole reaches a predetermined value. Further, the movable pin is arranged so that the opening is opened when the movable pin is retracted from the cavity, and the opening is closed by the tip when the movable pin is advanced in the cavity direction. The opening may be opened when the tip is projected into the cavity, and the opening may be closed by the tip when retracted from the cavity.

[0009]

Since the golf ball injection molding die of the present invention is constructed as described above, the opening area of the gas vent hole can be made large, and when the molding material is injected and introduced into the cavity, the air in the cavity is Is surely and smoothly discharged from the gas vent hole, so that it is possible to surely prevent the occurrence of air entry defects and weld defects in the golf ball, and
Immediately before the molding material introduced into the cavity penetrates the gas vent hole, the pin tip closes the opening, so that the occurrence of burrs in the gas vent hole can be prevented, and the appearance is good,
It is possible to form a golf ball that can omit or simplify post-processing.

Further, the tip end surface of the movable pin is formed into a hemispherical convex shape capable of forming a dimple of a golf ball or a concave shape capable of forming a land portion of a golf ball, and the tip end portion of the pin closes the opening. At this time, by forming a part of the mold cavity surface with the tip end surface, the opening area of the gas vent hole can be further increased, and post processing of the pin mark can be omitted or simplified. .

[0011]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5, the same components as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows an embodiment of a golf ball injection molding die of the present invention. In this embodiment, between the holding pins 4 and 4 of the upper die 1a and the lower die 1b, respectively. Gas vent holes 11 and 11 are formed so as to face each other (the holes 11 and 11 are preferably provided on or near the weld line). In this case, the gas vent hole 11,
Reference numeral 11 denotes openings 12 and 1 respectively communicating with the cavity 2.
The second side is formed into a small-diameter column 13 and 13, and the side opening to the outside is formed into a large-diameter column 14 and 14, and the movable pins 15 and 15 are movably disposed in the holes 11 and 11. These pins 15 and 15 are small-diameter cylindrical portions 13 of the holes 11 and 11,
Small diameter cylindrical parts 16 and 16 that can be fitted to the large diameter cylindrical parts 13 and the large diameter cylindrical parts 13 and 1 of the holes 11 and 11 that are continuously provided integrally therewith.
3 and a cylindrical base portion 17 having a diameter smaller than 3, pin movable devices 18, 18 are connected to the pins 15, 15, and the operation of the pin movable devices 18, 18 causes the pin 1 to move.
5, 15 retreat from the cavity 2 side in the holes 11, 11, and the tips of the small-diameter cylindrical portions 16, 16 of the pins 15, 15 recede from the rear ends of the large-diameter cylindrical portions 14, 14 of the holes 11, 11. By doing so, the openings 12, 12 are opened (see FIG.
(Exited state shown in (B)) or advanced from this position in the cavity direction, and the small-diameter cylindrical portions 16, 1 of the pins 15, 15 are
6 is fitted into the small-diameter cylindrical portions 13 and 13 of the holes 11 and 11, and the tip thereof reaches the end of the opening to close the openings 12 and 12 (shown in FIG. 1 (A)). Advancement status). Here, the movable devices 18, 18 are connected to a control device (computer) 19 of an injection molding machine (not shown), and the injection amount of the molding raw material into the cavity 2 of the mold 1 from the injection molding machine. When a predetermined value is reached (when the molding material is filled in the cavity 2), a signal is sent to the movable devices 18, 18 to move (advance) the movable pins 15, 15 toward the cavity 2 as described above. Moreover, before the molding material is injected into the mold cavity 2 from the injection molding machine, a signal is emitted to move the movable pins 15 and 15 out of the cavity 2 as described above.

The openings 12, 1 of the holes 11, 11 are
The diameter of 2 is not particularly limited, but when it is the same as the dimple diameter, it is preferably 1.5 to 4 mm.

The method of injection molding using the mold 1 is as follows.
Basically the same as the conventional method using the mold of FIG. 6,
In the present embodiment, the pins 15 and 15 are shown in FIG.
As shown in FIG. 3, the molding material is introduced into the cavity 2 with the openings 12, 12 left open. As a result, the air in the cavity 2 is quickly and surely discharged from the openings 12, 12, and the molding material is filled in the cavity 2. Then, a predetermined amount of molding material is injected from the injection molding machine to fill the cavity 2 with the molding material, and immediately before entering the holes 11 and 11, the movable devices 18 and 18 are moved by a signal from the control device 19. Has pins 15 and 15
Actuate toward the cavity 2,
The tips of the small-diameter cylindrical portions 16, 16 advance to the ends of the openings to close the openings 12, 12.

Therefore, according to this method, the cavity 2
Since the air inside is smoothly and surely discharged to the outside, the molding golf ball is unlikely to suffer from air-entry defects or weld defects, and the molding material may be pinned before entering the holes 11, 11. 15 small diameter cylindrical parts 16, 16
Is fitted into the small-diameter cylindrical portions 13, 13 of the holes 11, 11 and advances to the end of the opening to close the openings 12, 12, so that burrs are unlikely to occur.

In this case, the tip surface of the pin 15 is as shown in FIG.
As shown in FIG. 3, the pin 15 is formed in a hemispherical convex shape capable of forming a dimple of the golf ball, or as a concave shape capable of forming a land portion of the golf ball as shown in FIG.
It is preferable to allow the tip end surface of the pin 15 to form a mold cavity surface when it is advanced to the opening end of the pin. This makes it possible to increase the opening area of the opening 12 and eliminate pin marks. The post-processing is omitted or simplified. In the figure, 2a is a mold cavity surface, and 2b is a dimple forming convex portion. When the land portion is formed by the tip of the pin, the planar shape of the tip of the pin is not only circular but also polygonal such as triangle, square, rectangle, hexagon, octagon, etc. It may be formed in various shapes such as a letter shape, and the shape of the opening 12 may be changed accordingly.

Further, as shown in FIG. 4, the shape of the movable pin 15 is such that the tip portion 20 has a small-diameter columnar shape, and the intermediate portion 21 has a truncated cone shape.
The rear portion 22 has a large-diameter columnar shape, and the axial length of the large-diameter columnar rear portion 22 is formed to be longer than the total axial length of the small-diameter columnar front portion 20 and the truncated pyramid-shaped intermediate portion 21, and accordingly the hole 11 is formed. When the pin 15 is advanced, the rear portion 22 is first fitted to the large-diameter peripheral wall surface 11a of the hole 11 into which the pin 15 can be fitted, and the front portion 20 and the opening portion of the pin 15 are formed. The clearance formed by 12 and 12 is made as narrow as possible. Further, the tip 20 of the pin 15 can be accurately and concentrically arranged in the opening 12 (not biased). This makes it possible to further reduce the occurrence of burrs. Further, since the rubbing between the tip portion 20 and the inner surface of the opening portion 12 can be prevented, pin contamination does not occur.

Further, in the above-mentioned embodiment, when the pin 15 is withdrawn from the cavity 2, the opening 12 is opened and the cavity 2 is opened.
Although the opening 12 is configured to be closed when it advances in the direction, as shown in FIG. 5, when the molding material is filled in the cavity 2, the tip of the pin 15 is projected into the cavity 2 to open the opening. When the portion 12 is opened and the cavity 2 is filled with the molding material, the pin 15 may be retracted from the cavity 2 side so that the opening portion 12 is closed by the tip portion thereof.

Further, when the pin advances or retracts, the air pressure when air is discharged from the cavity into the hole 11 is detected, and when the air pressure reaches a predetermined value (eg, atmospheric pressure), the pin closes the opening. The movable device can also be operated as described above.

The type of golf ball molded according to the present invention is not particularly limited, and it may be a solid golf ball such as a one-piece, two-piece or three-piece golf ball or a thread-wound golf ball. It is suitable for injection molding. In this case, as shown in FIGS. 1 and 2, the cover can be formed by inserting the core into the cavity and injecting the molding material for the cover into the gap between the core and the wall surface of the cavity. The cover material may be injection-moldable and is not particularly limited.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications may be made without departing from the gist of the present invention.

[0022]

According to the present invention, since the opening area of the gas vent hole can be made large, the air in the cavity can be discharged reliably and smoothly, and weld defects and air entry defects are reduced. At the same time, burrs are less likely to occur in the gas vent hole. In addition, since air is satisfactorily released from the cavity, low-pressure injection and low-pressure mold clamping are possible, which reduces burrs from this point as well.
Therefore, post-processing is omitted or simplified because the number of hole traces and burrs is reduced, defects in subsequent processing steps are eliminated, and factors such as variations in the flight of golf balls due to post-processing can be reduced or eliminated. Is improved. Furthermore, since low-pressure injection and low-pressure mold clamping are possible as described above, a thin cover can be easily molded, and the life of the mold and molding machine is extended. Furthermore, by configuring the tip end surface of the pin to match the shape of the golf ball cavity so that dimples and land portions of the golf ball can be formed, the opening area of the gas vent hole can be increased and the pin trace No processing is required.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a mold according to an embodiment of the present invention,
(A) shows a state in which the opening is closed with a pin, and (B) shows a state in which the opening is open.

FIG. 2 is a partially omitted cross-sectional view showing another embodiment of the present invention,
An example in which the pin tip is formed in a hemispherical convex portion capable of forming dimples is shown.

FIG. 3 is a partially omitted cross-sectional view showing another embodiment of the present invention,
An example in which the tip of the pin is formed into a shape capable of forming a land portion is shown.

FIG. 4 is a partially omitted sectional view showing still another embodiment of the present invention.

5A and 5B show still another embodiment of the present invention, in which FIG. 5A shows a state in which the opening is opened, and FIG. 5B shows a state in which the opening is closed.

FIG. 6 is a schematic cross-sectional view of a conventional mold.

[Explanation of symbols]

 1 Mold 1a Upper mold 1b Lower mold 2 Cavity 3 Core 4 Holding pin 5 Molding material 11 Gas vent hole 12 Opening part 15 Movable pin 18 Pin moving device 19 Control device 20 Light part 21 Middle part 22 Rear part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B29D 31/00 7726-4F B29D 31/00 // B29L 31:54

Claims (9)

[Claims] 1. A method for injection molding a golf ball by introducing a molten injection molding material for a golf ball into a cavity of a mold, wherein a gas vent hole communicating with the cavity is formed in the mold. In the hole, a movable pin formed so that the tip portion can close the cavity side opening portion of the hole is movably arranged, and the tip portion of the pin does not block the opening portion. The molten molding material is injected and introduced into the cavity, the air in the cavity is discharged from the hole, and the pin is moved by moving the pin immediately before the molten molding material introduced into the cavity enters the hole. A golf ball injection molding method, characterized in that the opening is closed by the tip of the pin. 2. The tip surface of the movable pin is formed into a hemispherical convex shape capable of forming a dimple of a golf ball or a concave shape capable of forming a land portion of a golf ball, and the tip portion of the pin closes the opening. 2. The method according to claim 1, wherein the tip surface of the pin forms a part of the cavity surface of the mold to obtain a golf ball having a surface corresponding to the tip surface of the pin. 3. A golf ball injection molding mold having an upper mold and a lower mold, wherein the upper mold and the lower mold are separably joined to each other to form a hollow spherical cavity therein. A gas vent hole communicating with the cavity is formed in one or both of the
It is characterized in that a movable pin having a shape capable of closing the cavity side opening of this hole is movably arranged so that the opening can be opened and closed by the movement of the movable pin. Golf ball injection mold. 4. A tip end surface of the movable pin is formed into a hemispherical convex shape capable of forming a dimple of a golf ball or a concave shape capable of forming a land portion of the golf ball, and the tip end portion of the pin closes the opening. At this time, the die according to claim 3, wherein the tip surface constitutes a part of the die cavity surface. 5. The mold according to claim 3, wherein the movement of the movable pin toward the opening is started when the injection amount of the molding material by the injection molding machine reaches a predetermined value. 6. The method according to claim 3, wherein the movement of the movable pin toward the opening is started when the pressure of the air discharged from the cavity to the gas vent hole reaches a predetermined value. Mold. 7. The movable pin is arranged such that when the movable pin is retracted from the cavity, the opening is opened, and when the movable pin is advanced in the cavity direction, the distal end of the movable pin closes the opening. The mold according to any one of 6 above. 8. The movable pin has a small-diameter columnar front portion, a middle portion having a truncated cone shape, and a rear portion having a large-diameter columnar shape, and the axial length of the large-diameter columnar rear portion has a small-diameter columnar front portion and a truncated cone-shaped intermediate portion. The mold according to claim 7, wherein the mold is formed to have a shape longer than the total axial length of the movable pin and the hole, and the hole has a shape that can be fitted to the movable pin. 9. The movable pin is arranged such that when the tip of the movable pin is projected into the cavity, the opening is opened, and when retracted from the cavity, the tip is closed by the tip. The mold according to any one of 3 to 6.