JP2000116821A - Manufacture of golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the decentering of a core and to form a molding layer of uniform thickness by utilizing a conventional injection molding die even when a soft core is used and the thin molding layer is to be formed, by adjusting the tong hold of a supporting pin within a predetermined range of size is supporting a core ball on a center of a cavity. SOLUTION: A core ball 6 is placed in a spherical cavity of a die 1, and supported on a center of the cavity by a supporting pin 5, and a molding material is poured into a void between the core ball 6 and the die inner wall surface 10. On this occasion, a part of the core ball 6 is deformed by the supporting pin 5, and the deformation amount (tong hold) of the core ball 6 is optimized for supporting. That is, the tong hold Y (mm) is adjusted to be within a range of :A/4B-(0.1+A/10B)<=Y<=A/4B+(0.1+A/8B) when the flexible amount under 100 Kg load of the core ball 6 is A (mm), and the thickness of the molding layer formed by the molding material is B (mm), to be corresponded to the hardness of the core ball 6 and the thickness of the molding layer. Whereby the decentering of the core ball 6 can be prevented, and an uniform thin layer is injection-molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a golf ball capable of injection-molding a uniform thin layer on the surface of a solid core of a solid golf ball or a wound core of a wound golf ball.

[0002]

2. Description of the Related Art A golf ball has a solid type in which a spherical solid core of a rubbery elastic body is structurally covered with a cover made of a resin or the like, and a wound core in which a thread rubber layer is formed in a solid center. It is roughly classified into a thread-wound type whose surface is covered with a cover such as balata or resin. When a cover is formed on a core (core ball) using a resin such as a thermoplastic resin, any type of core is used. In general, the injection molding of the cover material is also performed for.

For example, FIG. 6 is a cross-sectional view of a mold 1 showing a conventionally known injection molding.
And a lower mold 3 having a two-part mold. By joining the split surfaces (parting lines) P of the upper and lower molds 2 and 3, a spherical cavity 4 is formed inside. The equatorial plane of the cavity 4 coincides with the position of the split plane P.

Here, the upper mold 2 and the lower mold 3 are provided with a plurality of support pins 5 each having a tip located very close to the spherical cavity 4, and a core ball disposed at the center of the cavity (the example shown in the figure). The core 6 is provided so as to be sandwiched between the tips of the support pins 5 from above and below.

The mold 1 shown in FIG. 6 has a runner 7 for supplying an injection material by joining the upper and lower molds 2 and 3, and a gate for introducing the molding resin supplied from the runner 7 into the cavity 4. 8 is provided. Further, at the pole (pole) position of the cavity 4, there are provided degassing means 9 comprising a pin a having a convex cross section and a gas vent hole b for passing the pin a, respectively. It is provided so that the gas in the cavity 4 is released from the gap formed therebetween.

In order to injection-mold a thermoplastic resin as a cover material on the core 6 using the mold shown in FIG. 6, the core 6 is placed in the cavity 4 and the core 6 is supported by the support pins 5 from above and below. Then, a thermoplastic resin is supplied from a supply source (not shown) to the runner 7 and the gate 8, and the resin 12 is placed in a space 11 between the surface of the core 6 and the inner wall surface 10 of the mold.
(Press-fitting).

In this case, the support pins 5 for supporting the core 6
Is gradually retracted in accordance with the state of introduction of the material so as to reach the level of the mold wall surface 10 (the pin tip corresponds to a desired shape of the molding surface) at the end of or immediately before the end of the material injection, and to supply the resin. The injection molding is ended by ending.

Although not shown, a large number of protrusions for molding dimples are arranged on the mold inner wall surface 10 constituting the cavity 4, and a large number of protrusions are formed on the surface of the golf ball when injection molding is completed. The dimples are formed.

[0009]

When the state before injection of the mold 1 shown in FIG. 6 is enlarged by taking only the center of the cavity, as shown in FIG.
Each of the support pins 5 is disposed at the center of the cavity while the vicinity of both poles is supported by the tip of each support pin 5. In this case, usually, the tip of the support pin 5 is press-fitted enough to support the core, and the core 6 is hardly deformed.

[0010] In recent years, with the softening of golf balls, the core hardness of a solid core has become particularly soft, and a thin cover has been required. On the other hand, the mold gate is provided by joining the split molds as in the above-mentioned type, or even if it is a tunnel gate formed only on one split mold, the purpose of the gate cut is Therefore, an injection port is often provided very close to the split surface, and the internal pressure is 400 to 20 at the time of injection molding.
A resin of 00 kg / cm ² or more is supplied to the core.

For this reason, when the core is hard and the cover has a large thickness, the eccentricity of the core does not occur if the gate material of the cover material is balanced, but when the core is soft, the core is shown in FIG. As described above, the core surface close to the gate is partially deformed by the injection pressure, which may cause a problem that eccentricity and unevenness of the formed cover thickness may occur.

The reason for this is that if the core is soft, deformation and blurring at the time of injection become large, and the eccentricity is easily caused due to a slight imbalance of the gates made of resin.

Further, when the cover is to be formed thin with the above-described mold, the gap at the deepest portion (in the vicinity of the cavity) of the cavity becomes small due to the deformation of the core as described above, and the cover thickness at this portion becomes thin. In other words, there is also a problem that when the cover is formed into a cover having a thickness of 1.3 mm or less, particularly 1.0 mm or less, a filling failure is likely to occur.

[0014] The present invention has been made in view of the above problems, and uses a relatively soft core.
In particular, even when a thin molding layer of 1.0 mm or less is formed, a golf ball capable of forming a molding layer having a uniform thickness by using a conventional injection mold to avoid eccentricity of the core. It is an object of the present invention to provide a method for producing the same.

[0015]

The present invention provides the following method for manufacturing a golf ball to achieve the above object. Claim 1: A spherical cavity is formed in the inner wall surface, a plurality of split molds having a split surface at a position substantially coincident with the equatorial plane of the spherical cavity, and a plurality of split dies are provided in a direction perpendicular to the equatorial plane. Using a mold provided with a support pin capable of moving forward and backward, a core ball is put in the spherical cavity, the core ball is supported at the center of the cavity by the support pin, and a space between the core ball surface and the mold inner wall surface is formed. In the method of manufacturing a golf ball in which a molding layer is formed on the surface of a core sphere by introducing a molding material into the void, when the core sphere is supported at the center of the cavity, the core sphere may be 10
Assuming that the amount of deflection when pressed at 0 kg is A (mm) and the thickness of the formed layer is B (mm), the allowance for gripping each support pin (the amount of deformation of the core sphere by each support pin) Y (mm) ) Is adjusted so as to satisfy the following range (1). A / 4B− (0.1 + A / 10B) ≦ Y ≦ A / 4B +
(0.1 + A / 8B) Claim 2: The mold comprises two split dies, each of the split dies having at least three support pins, and these support pins are equally spaced around the pole center of the cavity. The method for manufacturing a golf ball according to claim 1, wherein the golf ball is spaced apart. In a third aspect, when a region that completely surrounds all the support pins arranged in the same split mold in the vertical direction is a virtual region, the support pins are arranged so that the minimum virtual region is 60 to 450 mm ^2. The method of manufacturing a golf ball according to claim 1, wherein the golf ball is provided. Preferably, the support pins are arranged such that the total cross-sectional area of all the support pins, in which the dies are arranged in the same split mold, is 20 to 100 mm ^2. The manufacturing method of the golf ball of the description.

That is, the inventor of the present invention has a plurality of split dies which form a spherical cavity on the inner wall surface, has a split surface at a position substantially coincident with the equatorial plane of the spherical cavity, and Using a mold provided with a plurality of support pins that can move forward and backward in the vertical direction, a core ball is put in the spherical cavity, the core ball is supported at the center of the cavity by the support pin, and the surface of the core ball and the mold By introducing the molding material into the space between the inner wall surface, when forming the molding layer on the core sphere surface, the hardness of the core sphere on which the molding layer is formed, the desired thickness of the layer to be molded Accordingly, by optimizing the grip allowance of the support pin that supports the core ball, eccentricity does not occur especially for the softened core ball, and injection molding of a thin cover to a uniform thickness And a thin layer such as an intermediate layer other than the cover can be formed. The present invention has been found to be applicable to both cases, and to be able to be favorably injection-molded on a solid core having a single layer or a multilayer structure of a solid golf ball, a wound core of a thread-wound golf ball, or a cover having a multilayer structure. It is a thing.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail.

As described above, the method of manufacturing a golf ball of the present invention involves injection molding using a conventionally known injection mold.

That is, the injection mold used in the present invention is:
As in the injection molding die 1 shown in FIG. 6 described above, a spherical cavity 4 is formed on the inner wall surface, and a plurality of split dies 2 and 3 having a split surface at a position substantially coincident with the equatorial plane of the spherical cavity 4. 6 (in the example of FIG. 6) and a plurality of support pins that pass through the split mold and are provided in a direction perpendicular to the equatorial plane.

Hereinafter, the structure of the mold 1 will be described with reference to FIG.
Are denoted by the same reference numerals, and description thereof will be omitted.

According to the manufacturing method of the present invention, a core ball 6 (solid core in the illustrated example) is placed in the spherical cavity 4 of the mold 1, and the core ball 6 is supported at the center of the cavity by the support pin 5,
The molding material is introduced into the space 11 between the surface of the core ball 6 and the inner wall surface 10 of the mold. However, since the injection molding layer can be made thinner as described later, the outer layer cover, the inner layer cover, In order to form the layers up to the layer, the present invention is applied to a single-layer or multi-layer core of a solid golf ball, a wound core formed by winding a wound rubber around a solid center or a liquid center of a wound golf ball, and the like. As the molding material, a cover material or an intermediate layer material currently used for golf balls, such as an ionomer resin, a polyetherester, a thermoplastic resin such as a polyurethane resin or a polyamide resin, can be used.

The method of manufacturing a golf ball according to the present invention requires that the core ball 6 contacting the support pin 5 be supported in a partially deformed state.

That is, FIG. 1 is a partially enlarged cross-sectional view showing a core ball disposed in the mold 1, and uses an injection molding die of a type in which the core ball is supported by the support pins 5. When the above-mentioned core ball 6 is supported, the conventional example (for example, FIG.
Rather than simply supporting the core sphere 6 at the center of the cavity without causing the core sphere 6 to bend as in the case of the method described above, a part of the core sphere is deformed by the support pin 5 and the amount of deformation of the core sphere (hereinafter, referred to as This is called "grasping allowance".

Here, the grip allowance Y (mm) of the present invention is:
When the amount of deflection A (mm) of the core ball under a load of 100 kg and the thickness of the formed layer are B (mm), the following range A / 4B− (0.1 + A / 10B) ≦ Y ≦ A / 4B +
(0.1 + A / 8B), and it is necessary to match the hardness of the core sphere and the thickness of the molded layer. If the grip allowance is smaller than the above value, the core deformation due to the injection pressure and the subtle momentum of the gate balance,
If the core is apt to be eccentric and has a large value, the core is chipped due to the pin touching the core, or the core is excessively deformed, and the space 11 near the gate 8 is narrowed, and the molding material is difficult to enter. The mold internal pressure (injection pressure) becomes unnecessarily high.

The amount of deflection of the core sphere means the amount of deformation that occurs when the core sphere is placed on a flat surface and a load of 100 kg is applied through a flat plate.

In the manufacturing method of the present invention, the core ball is supported by adjusting the above-mentioned gripping margin. In this case, as shown in FIG. The contact state is defined as a fixed position, and the core ball 6 is deformed by pressing with the support pin 5 so as to have a value specified within the above range with reference to this position, as shown in FIG.
The distance between the fixed position (broken line) and the deformed core ball (solid line) is set to the specified allowance.

Here, the setting of the gripping margin is performed for each support pin, but since it is determined by the hardness of the core ball and the thickness of the molding layer, the support pins arranged in the same split mold are set. Are set so as to have the same gripping margin even if the length and the cross-sectional area are different.

The mold used in the present invention may be any mold having a plurality of split molds which are conventionally known. In order to improve the injection conditions, the mold is composed of two split molds having the same shape. Preferably, it is a split type.

The number of support pins provided in each split mold can be appropriately selected according to the supporting state of the core sphere, but three or more, especially 3 to 5 pins are arranged in each split mold. Sometimes it is provided perpendicular to the equatorial plane (split mold joining surface) of the spherical cavity formed inside, but in this case, the tips of the pins are arranged at equal intervals around the pole of the cavity Is preferably performed.

In the present invention, furthermore, when a region which completely surrounds all the support pins arranged in the same split mold in the vertical direction is a virtual region, the minimum virtual region is 60 to 450 m.
m ^2, it is preferable to so particularly in 80～300Mm ^2, is less than 60 mm ^2, when the core holding, may not be held in the center. On the other hand, when the diameter exceeds 450 mm ² , an error of the gripping margin with respect to the outer diameter of the core becomes large, the eccentricity becomes easy, and when used as a pin for forming a dimple at the tip, the dimple becomes elliptical, which is not preferable.

Here, a specific example of the minimum virtual area will be described with reference to FIG. 4. FIG. 4 is a front view of one split mold as viewed from the inner wall side, and the tips of three support pins 5 They are arranged at equal intervals so as to be located concentrically around the pole p of the cavity 4.

The minimum virtual area referred to in the present invention is a virtual plane T (where the support pins 5 are 3) formed by connecting three support pins from the outside (to be in contact with each other) with a straight line on the same plane. In the case of a book, the shape is almost a regular triangle)
In the case where there are four support pins, the virtual plane connected by straight lines circumscribing each pin has a shape similar to a square, and similarly, when there are five or more support pins, the minimum The virtual region is a planar region similar to a regular pentagon or more regular polygon.

In the present invention, the total sectional area of the support pins arranged in the same split mold is 20 to 100 mm ² , especially 20
It is preferably adjusted to be ~75mm ^2. If the total cross-sectional area is less than 20 mm ² , the pin will stick to the core and the core will be easily chipped. On the other hand, if the total area is more than 100 mm ² , the flow of the molding material will be poor with respect to the position supported by the pin, and the ball will have durability May decrease.

In the production method of the present invention, other conditions are not particularly limited as long as the above requirements are satisfied, and injection molding can be performed according to a known method. Therefore, in injection molding, an appropriate molding material may be supplied in the order of the runner 7 and the gate 8 and introduced into the cavity.

In this case, the molding material injected from the gate 8 hits the nearest core ball 6 while maintaining a high injection pressure, so that the pin 5 supporting the core ball is restored with the momentum, When the support pins are pushed outward and the core ball returns to the original spherical shape, and the filling of the space is completed, the shape of the core ball is completely restored (FIG. 5).

Therefore, according to the production method of the present invention, a molded layer having a uniform thickness can be formed without eccentricity of the core sphere due to the injection pressure.
In particular, injection molding can be easily performed only by adjusting the grip allowance, even when the thickness is as thin as 1.0 mm or less.

The mold used in the present invention can be appropriately selected depending on the type of the molding layer to be formed on the core ball. For example, when the molding layer is a cover, it is not shown in the drawings. On the inner wall surface, those having a large number of protrusions for molding dimples can be used.

When a core having a multilayer structure is manufactured by injection molding, for example, when a solid core having a multilayer structure composed of a plurality of layers having different physical properties is manufactured, an inner layer of a cover is formed on the core. In such a case, or when the outer layer is further coated on the inner layer, a mold having a flat inner wall surface can be selected and used.

Further, the type of the gate of the mold is not limited to the type formed at the time of joining the split molds described above, and the type of the gate may be a tunnel gate formed inside one split mold. Good.

The embodiment of the present invention will be described. In this embodiment, a core ball 6 (elastic spherical core in this embodiment) is supported by a support pin before injection molding as shown in FIG. By joining the upper and lower mold halves 2, 3, a spherical cavity 4 is provided inside, and a split surface P is provided at a position coincident with the equatorial plane of the cavity 4.
In this method, injection molding is performed using a mold 1 having three support pins 5 so as to be able to advance and retreat in a direction perpendicular to the equatorial plane.

The mold 1 supports a spherical elastic core 6 as a core ball at the center of the cavity 4 by respective support pins 5, and a cavity 1 formed between the core 6 and the mold wall surface.
1, the runner 7 and the gate 8 formed on the split surface P
The molding is performed by injecting a molding material (in this example, a cover material such as an ionomer resin) through the mold. Although not shown, the position of the gate 8 is determined by dividing the upper and lower molds 2 and 3. It is provided with six locations equidistantly spaced about the plane P.

In this embodiment, when the core 6 is supported by the support pin 5, the core 4 is urged by the pin until it is partially deformed as shown in FIG. As a result, the core 4 is pressed in the axial direction of the support pin 5, that is, in the upward and downward directions, and expands and deforms in the equator direction, and the gap between the voids 11 formed on the wall surface of the core 4 and the mold 1 is , Support pin 5
Is increased in the area near the poles where the sword is provided, and decreases near the equator near the gate 8 (FIG. 1).

In this case, as shown in FIG. 2, the gripping margin Y of the support pin 5 is changed from the position where the support pin 5 comes into contact without deforming the core 6 as shown in FIG. It is deformed and supported. That is, FIG. 2 is a partially enlarged view showing a state where the tip of the support pin 5 is in contact with the solid core 6. Conventional injection molding core 6
Are mostly supported in this position and injection is taking place. On the other hand, in the present invention, the state of supporting the core by the support pins 5 is not limited to the position shown in FIG. 2, and the core 6 is further pressed into the state shown in FIG. Things. That is, as shown in FIG. 3, by pressing each support pin 5 in the axial direction, the original surface shape of the core 6 shown by the broken line becomes a concave portion of the deformation amount Y (mm) at the position shown by the solid line. Deformed and supported.

Here, the deformation amount Y (mm) of the core, that is, the allowance Y (mm) of the support pin is 100 k of the core.
Assuming that the amount of deflection A (mm) when the g load is applied and the thickness of the cover to be formed is B (mm), the values are adjusted to the values shown in the following ranges as described above. A / 4B− (0.1 + A / 10B) ≦ Y ≦ A / 4B +
(0.1 + A / 8B)

In this embodiment, the amount of deflection of the core under a load of 100 kg is 4.0 mm, the desired thickness of the cover layer to be formed is 1.3 mm, and the gripping margin is 0.77 mm.
And

FIG. 4 is an enlarged plan view showing the arrangement of the support pins 5 when the upper mold 2 or the lower mold 3 is viewed from the inner surface of the mold in the examples of FIGS.

In FIG. 4, the tips of the three support pins 5 are arranged at equal intervals on a concentric circle around the pole p. Then, in this case, the area of an imaginary plane (substantially close to an equilateral triangle) that is in equilibrium with the equatorial plane (partition plane of the mold) of the cavity formed when the support pins are connected by straight lines so as to circumscribe each pin is It is in the range of 139.3 mm ² . Further, in FIG. 4, the total cross-sectional area of the support pins indicated by oblique lines is 30.5 mm ² .

[0048]

According to the method of manufacturing a golf ball of the present invention, a uniform thin layer can be injection-molded on the surface of a solid core or the like of a solid golf ball while avoiding eccentricity.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a base point of a grip margin in the same example.

FIG. 3 is an explanatory diagram showing a grip allowance in the same example.

FIG. 4 is an explanatory diagram showing a virtual plane according to the present invention.

FIG. 5 is a partially enlarged view showing the inside of a mold after injection molding of the present invention.

FIG. 6 is a schematic view showing an injection mold.

FIG. 7 is a partially enlarged view showing a conventional supporting method.

FIG. 8 is a partially enlarged view showing a state where a core of a conventional example is deformed.

[Description of Signs] 1 Mold 2 Upper mold 3 Lower mold 4 Cavity 5 Support pin 6 Core ball

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Michio Inoue 20 Onohara, Chichibu City, Saitama Bridgestone Sports F-term (reference) 4F206 AA22 AA24 AA29 AA31 AA32 AA42 AD05 AD18 AG19 AH61 AR12 AR20 JA07 JB12 JF05 JF35 JL02 JM04 JQ81

Claims (4)

[Claims] 1. A spherical cavity is formed on an inner wall surface, a plurality of split molds having a split surface at a position substantially coincident with an equatorial plane of the spherical cavity, and a plurality of split molds perpendicular to the equatorial plane. The core ball is put into the spherical cavity by using a mold having a support pin that can move forward and backward, and the core ball is supported at the center of the cavity by the support pin. By introducing the molding material into the void,
In the method of manufacturing a golf ball in which a molding layer is formed on the surface of a core ball, when the core ball is supported at the center of the cavity, the core ball is formed by one
Assuming that the deflection amount when pressed at 00 kg is A (mm) and the thickness of the formed layer is B (mm), the allowance for gripping each support pin (the amount of deformation of the core sphere by each support pin) Y (mm) ) Is adjusted to fall within the following range. A / 4B− (0.1 + A / 10B) ≦ Y ≦ A / 4B +
(0.1 + A / 8B) 2. The mold according to claim 1, wherein the mold comprises two split molds.
The split molds each include at least three support pins,
2. The method of manufacturing a golf ball according to claim 1, wherein the support pins are arranged at equal intervals in the pole center of the cavity. 3. When the area in which the mold completely surrounds all the support pins arranged in the same split mold in the vertical direction is a virtual area, the support pins are set so that the minimum virtual area is 60 to 450 mm ^2. The method for manufacturing a golf ball according to claim 1, wherein the golf ball is disposed. 4. The support pin according to claim 1, wherein the support pins are arranged such that the total cross-sectional area of all the support pins arranged in the same split mold is 20 to 100 mm ^2. 9. The method for producing a golf ball according to the above item.