Golf ball and method of manufacturing the golf ball

Abstract

To provide a golf ball being moldable highly accurately in a performance and aesthetic property even in a case of reducing the weight of the ball, and a manufacturing method of the golf ball.SOLUTION: A golf ball 100 includes a core spherical body 101 and an outer surface body 110. The core spherical body 101 is composed of a thermoplastic ionomer resin with bending rigidity of 320 MPa. An outermost layer 103 of the core spherical body 101, coming into contact with an inner surface of the outer surface body 110 is composed of a solid body without air bubble 102. Alternatively, in the core spherical body 101, an inner layer 104 located inward the outermost surface layer 103 is composed of a porous body with numerous air bubbles 102. In that case, the inner layer 104 is so formed that the size of the bubble 102 increases toward the central part of the core spherical body 101.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a golf ball for use in ground golf or park golf, and a method for manufacturing the golf ball. [Background technology]

[0002] Various golf balls for use in ground golf and park golf have been proposed. For example, Patent Document 1 below discloses a two-layer resin ball with a first core and a second core made of a foamed resin material and a solid skin that does not contain any foam bubbles formed on the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-237479

[0004] However, the resin ball described in Patent Document 1 has a problem in that if the expansion ratio of the foamed resin is increased to reduce the weight of the ball, the foamed resin portion will deform during injection molding of the skin, making it impossible to mold the ball with precision in terms of performance and aesthetics.

[0005] The present invention has been made to address the above-mentioned problems, and its object is to provide a golf ball and a method for manufacturing a golf ball that can be molded with high precision in terms of performance and aesthetics even when the ball is lightweight. Summary of the Invention

[0006] In order to achieve the above object, the present invention is characterized by a golf ball for ground golf or park golf, which includes a core spherical body made of an ionomer resin sphere, and a skin body made of an ionomer resin that covers the outer surface of the core spherical body and forms the outer surface of the golf ball, the skin body being formed to a thickness of 4 mm or less, and the core spherical body having a surface layer in contact with the inner surface of the skin body having a bending rigidity of at least 300 MPa or more. Made of resin material In addition, the outermost layer, which is at least 1 mm deep from the surface that contacts the inside surface of the skin body, is made of a solid body that does not contain any bubbles, and the inner layer that is deeper than the outermost layer is made of a porous body that contains countless bubbles, and these outermost layer and inner layer are formed integrally.

[0007] According to the features of the present invention configured in this manner, the golf ball has a skin body formed to a thickness of 4 mm or less, and the surface layer of the core body that contacts the inner surface of the skin body is made of a resin material with a bending rigidity of at least 300 MPa. Therefore, even if the golf ball is made lighter, deformation of the core body is suppressed, and the entire golf ball can be molded with precision in terms of both performance and aesthetics.

[0008] Furthermore, according to the features of the present invention configured as described above, the golf ball has an outermost layer of the core spherical body, which is at least 1 mm deep from the surface that contacts the inner surface of the skin body, and is composed of a solid body that is free of air bubbles, and an inner layer inside the outermost layer is composed of a porous body that contains numerous air bubbles, thereby making it possible to reduce the weight of the golf ball while effectively suppressing deformation of the core spherical body and accurately molding the entire golf ball in terms of both performance and appearance.Furthermore, if the outermost layer of the golf ball is composed of a translucent or opaque material, air bubbles in the inner layer are prevented from appearing on the exterior, thereby improving the aesthetic appearance of the golf ball.

[0009] Another feature of the present invention is that in the golf ball, the inner layer is formed with larger bubbles toward the center.

[0010] According to the features of the present invention configured as described above, the size of the air bubbles in the inner layer of the golf ball increases toward the center, which allows the golf ball to be made lighter while effectively suppressing deformation of the core sphere, thereby enabling the entire golf ball to be molded with precision in terms of both performance and aesthetics.In addition, the golf ball can be made lighter while preventing the air bubbles in the inner layer from being noticeable in appearance.

[0011] Another feature of the present invention is that in the golf ball, the core sphere is formed to have a weight of 35 g or more and 55 g or less.

[0012] According to the features of the present invention, the golf ball has a core spherical body weighing between 35g and 55g, which allows the golf ball to be made lighter overall, specifically, easily molded while maintaining the aesthetic appearance of a golf ball weighing 85g or less, particularly 75g to 80g. In this case, a golf ball weighing between 75g and 80g is less likely to sink into the turf, particularly on turf, reducing rolling resistance and also making it easier to control the flight distance due to its small moment of inertia.

[0013] In addition to the above configuration, the golf ball may further include: The core sphere is made up of a porous material with countless air bubbles throughout. can be .

[0014] According to this, The entire core of the golf ball is made of a porous material containing countless air bubbles, which allows the golf ball to be made lighter while suppressing deformation of the core, thereby enabling the entire golf ball to be molded with high precision in terms of both performance and aesthetics.

[0015] Also, in this case, In the golf ball, the core has an internal space portion, which is a single space centered on the center of the core, inside the surface layer. Good .

[0016] According to this, The golf ball has an internal space inside the surface layer of the core sphere, which is a space centered on the center of the core sphere. This allows the golf ball to be made lighter while effectively suppressing deformation of the core sphere, thereby enabling the entire golf ball to be molded with precision in terms of performance and aesthetics.

[0017] In these cases, the core sphere of the golf ball has an internal support member that is installed within the internal space and supports the core sphere from the inside. Good .

[0018] According to this, The golf ball has an internal support body that is installed within the internal space of the core sphere and supports the core sphere from the inside, making it possible to reduce the weight of the golf ball while effectively suppressing deformation of the core sphere, thereby enabling the entire golf ball to be molded with precision in terms of performance and aesthetics.

[0020] Furthermore, the present invention can be embodied not only as an invention of a golf ball, but also as an invention of a method for manufacturing a golf ball.

[0021] Specifically, the present invention relates to a method for manufacturing a golf ball for ground golf or park golf, the method comprising the steps of: Made of ionomer resin A core sphere molding process for molding a core sphere made of a sphere, and a process for covering the outer surface of the core sphere to form the outer surface of the golf ball. Made of ionomer resin and a skin molding step of molding a skin body, in which a foamed resin material having a bending rigidity of at least 300 MPa or more is injected into a mold at a temperature of 10°C or higher and 50°C or lower to mold a surface layer that contacts the inner surface of the skin body, and the outermost surface layer that is at least 1 mm deep from the surface that contacts the inner surface of the skin body is molded as a solid body that does not have any bubbles, and the inner layer inside the outermost surface layer is molded as a porous body that has numerous bubbles. Furthermore, these outermost and inner layers are integrated. In the skin forming step, the skin may be formed to a thickness of 4 mm or less, and the same effects as those of the above embodiment can be expected.

[0023] In this case, in the golf ball manufacturing method, the core sphere may be formed to a weight of 35 g or more and 55 g or less in the core sphere molding step, which can also be expected to achieve the same effects as the above embodiment. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a half cross-sectional view showing an outline of the external and internal configurations of a golf ball according to one embodiment of the present invention. [Figure 2] 2 is a cross-sectional view schematically showing the configuration and molding process of a core sphere molding die for molding the core sphere of the golf ball shown in FIG. 1. FIG. [Figure 3] 2 is a cross-sectional view schematically showing the configuration of a skin molding die for molding the skin of the golf ball shown in FIG. 1. FIG. [Figure 4] 4 is a cross-sectional view schematically showing the process of forming a skin body using the skin body forming mold shown in FIG. 3. FIG. [Figure 5] FIG. 10 is a half cross-sectional view showing the outline of the external and internal configurations of a golf ball according to a modified example of the present invention. [Figure 6] FIG. 10 is a half cross-sectional view showing the outline of the external and internal configurations of a golf ball according to another modified example of the present invention. [Figure 7] FIG. 10 is a half cross-sectional view showing the outline of the external and internal configurations of a golf ball according to another modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of a golf ball according to the present invention will now be described with reference to the drawings. FIG. 1 is a half-sectional view showing the outline of the external and internal configuration of a golf ball 100 according to the present invention. Note that the drawings referred to in this specification are schematic, with some components exaggerated to facilitate understanding of the present invention. Therefore, the dimensions and proportions of the components may differ. This golf ball 100 is a game ball with a diameter of 60 mm that is hit with a club in ground golf or park golf.

[0026] (Configuration of Golf Ball 100) Golf ball 100 is primarily comprised of core 101 and skin 110. Core 101 is a component that constitutes the interior of golf ball 100 and is comprised of a sphere. Core 101 is made of a foamed resin material obtained by adding a foaming agent to various resin materials, such as thermoplastic ionomer resin, thermoplastic polyurethane elastomer, or ABS resin. In other words, core 101 is made of a porous body in which countless bubbles 102 are formed due to foaming that occurs when the foamed resin material hardens.

[0027] In this case, the core sphere 101 is made by foaming a resin material with a bending rigidity of 300 MPa or more. Here, bending rigidity is a value calculated by multiplying the moment of inertia of the resin material molded into a plate shape by Young's modulus (elastic modulus); the larger this value, the less flexible the material is. This bending rigidity can be calculated experimentally in accordance with the Japanese Industrial Standard "JIS K 7106," but can also be obtained for each type of material from the manufacturer of the resin material. In this embodiment, the core sphere 101 is made of a thermoplastic ionomer resin with a bending rigidity of 320 MPa.

[0028] Furthermore, this core sphere 101 has an outermost surface layer 103 in contact with the inner surface of the skin body 110, which is composed of a solid body without bubbles 102, and an inner layer 104 inside this outermost surface layer 103, which is composed of a porous body with countless bubbles 102. In this embodiment, the outermost surface layer 103 is the portion up to a depth of 1 mm from the surface of the core sphere 101. In Figure 1, the outermost surface layer 103 is indicated by thick hatching.

[0029] Furthermore, the inner layer 104 is formed so that the size of the bubbles 102 gradually increases toward the center of the core sphere 101. In this case, the size of the bubbles 102 is preferably about 5 mm or less at the center of the core sphere 101, but in this embodiment, the bubbles 102 are formed to a size of about 1 mm to 2 mm at the center of the core sphere 101. Note that although the bubbles 102 are depicted as circular in FIG. 1, in reality, the bubbles include bubbles of various irregular shapes (non-uniform, irregular shapes).

[0030] Skin 110 is a component of golf ball 100 that covers the entire outer surface of core sphere 101 and is made of a transparent or translucent resin material. In this embodiment, skin 110 is made of a transparent ionomer resin. Skin 110 is formed with a uniform thickness of 4 mm or less. In this embodiment, skin 110 is formed with a thickness of 2 mm. As a result, golf ball 100 has core sphere 101 with a diameter of 56 mm.

[0031] (Manufacturing 100 golf balls) Next, a method for manufacturing the golf ball 100 configured as described above will be described. First, an operator manufactures the core sphere 101. Specifically, as shown in FIG. 2, the operator prepares a core sphere molding die 200 for molding the core sphere 101. As shown in FIG. 2, the core sphere molding die 200 is composed of a pair of a first mold 210 and a second mold 220 for molding each half (hemisphere) of the core sphere 101.

[0032] The first mold 210 and the second mold 220 are respectively formed with a first molding section 211, a second molding section 221, and sprue sections 230a and 230b. The first molding section 211 and the second molding section 221 are sections that mold the respective shapes of one half (hemisphere) of the core sphere 101, and are formed into concave hemispherical shapes that are the inverse of these shapes. The sprue sections 230a and 230b are flow paths that guide the foaming resin material from the outside of the first mold 210 and the second mold 220 into the first molding section 211 and the second molding section 221, respectively.

[0033] More specifically, sprue portions 230a, 230b are formed as grooves recessed into the mating surfaces (parting surfaces) of first mold 210 and second mold 220, and these grooves are arranged opposite each other to form elongated tubes serving as flow paths. In this embodiment, sprue portions 230a, 230b are formed to extend in opposite directions relative to first molding portion 211 and second molding portion 221.

[0034] Next, an operator attaches the core sphere molding die 200 to a known injection molding machine (not shown) and operates the injection molding machine to injection-mold the core sphere 101. Here, the injection molding machine is primarily equipped with a mold clamping unit (not shown) that opens and closes the first mold 210 and the second mold 220, and an injection unit 240 that injects molten foam resin material into each of the sprues 230a and 230b. Therefore, the injection molding machine molds the core sphere 101 by injecting molten resin material from the injection unit 240 into the core sphere molding die 200, which has the first mold 210 and the second mold 220 closed.

[0035] In this case, the worker injects the foaming resin material into the cooled first mold 210 and second mold 220. As a result, within the core sphere molding die 200, the foaming resin material in contact with the first molding section 211 and the second molding section 221 hardens without foaming, while the foaming hardens in a state where it is more advanced toward the center of the first molding section 211 and the second molding section 221. In other words, the worker can configure the outermost surface layer 103 of the core sphere 101 as a solid body without bubbles 102, and can configure the inner layer 104 inside this outermost surface layer 103 as a porous body with countless bubbles 102. In this case, the outermost surface layer 103 is formed to be translucent in this embodiment.

[0036] Here, the temperature of each of the first mold 210 and the second mold 220 is preferably 10°C or higher and 50°C or lower, more preferably 30°C or lower, and even more preferably 20°C or lower. In this embodiment, the temperature of each of the first mold 210 and the second mold 220 is 15°C. In this case, the worker can heat the first mold 210 and the second mold 220 to a temperature close to the melting temperature of the foaming resin material, specifically, to a temperature 10°C to 20°C lower than the melting temperature, thereby foaming the foaming resin throughout the first molding section 211 and the second molding section 221 and forming bubbles 102 throughout the core sphere 101. In other words, the worker can control the size of the bubbles 102 formed on the surface of the core sphere 101 by appropriately setting the temperature of each of the first mold 210 and the second mold 220 depending on the type of foaming resin material.

[0037] Next, when the foamed resin material in the core sphere molding die 200 has sufficiently hardened, the worker opens the first die 210 and the second die 220 and removes the core sphere 101. In this case, the core sphere 101 is formed by foaming a resin material with a bending rigidity of 320 MPa, but the bending rigidity of the outermost surface layer 103 does not need to be formed to 320 MPa.

[0038] That is, since the inner layer 104 of the core sphere 101 is composed of a porous material, the outermost surface layer 103 is usually formed to have a bending rigidity of less than 320 MPa. The bending rigidity of this outermost surface layer 103 can be adjusted by the expansion ratio of the foamed resin material, and according to experiments by the inventors, the expansion ratio of the foamed resin material is preferably 1.16 or more and 1.83 or less. In this embodiment, the core sphere 101 is formed to weigh 35 g. The process of molding this core sphere 101 corresponds to the core sphere molding process according to the present invention.

[0039] Next, the worker forms the skin body 110 on the outer surface of the core sphere 101. Specifically, the worker prepares a skin body forming mold 300 for forming the skin body 110. As shown in Fig. 3, the skin body forming mold 300 is composed of a pair of a first mold 310 and a second mold 320 for forming each half (hemisphere) of the core sphere 101.

[0040] First mold 310 and second mold 320 are respectively formed with first molding section 311, second molding section 321, and sprue sections 330a and 330b. First molding section 311 and second molding section 321 are sections that mold the respective shapes of one half (hemisphere) of skin body 110, and are formed into concave hemispherical shapes that are the inverse of these shapes. Sprue sections 330a and 330b are flow paths that guide resin material from the outside of first mold 310 and second mold 320 into first molding section 311 and second molding section 321, respectively.

[0041] More specifically, sprue portions 330a, 330b are formed as grooves recessed into the mating surfaces (parting surfaces) of first mold 310 and second mold 320, and these grooves are arranged opposite each other to form elongated tubes serving as flow paths. In this embodiment, sprue portions 330a, 330b are formed to extend in opposite directions relative to first molding portion 311 and second molding portion 321.

[0042] Support pins 340a and 340b are provided on first mold 310 and second mold 320, respectively. Support pins 340a and 340b are rods that support core sphere 101 in a floating state within skin molding mold 300 and also function as ejection pins when removing golf ball 100 from first mold 310 and second mold 320.

[0043] Next, an operator attaches the skin body molding die 300 to a known injection molding machine (not shown) and operates the injection molding machine to injection mold the skin body 110. Here, the injection molding machine is mainly configured with a mold clamping unit (not shown) that opens and closes the first mold 310 and the second mold 320, and an injection unit 350 that injects molten foamed resin material into the sprues 330a and 330b. Therefore, the injection molding machine molds the skin body 110 by injecting molten resin material from the injection unit 350 into the skin body molding die 300, which has the first mold 310 and the second mold 320 closed.

[0044] Specifically, the worker operates the injection molding machine to protrude support pins 340a and 340b within first mold 310 and second mold 320, respectively, and causes these support pins 340a and 340b to support core sphere 101 in a suspended state within first mold 310 and second mold 320. Then, as shown in Fig. 4, the worker operates the injection molding machine to inject molten resin material from injection unit 350 into skin body molding mold 300, which has first mold 310 and second mold 320 closed.

[0045] In this case, the injection molding machine injects molten resin material into the skin body molding die 300, and then retracts the support pins 340a, 340b from the first mold 310 and the second mold 320 at a predetermined timing, thereby molding the spherical skin body 110 around the core sphere 101. In this case, since the core sphere 101 is made of a resin material with a bending rigidity of 320 MPa, deformation due to the pressure of the resin material injected into the skin body molding die 300 is prevented, and the skin body 110 is molded while maintaining its spherical shape.

[0046] Next, after molding skin body 110, the worker operates the injection molding machine to open first mold 310 and second mold 320, thereby removing golf ball 100 with molded skin body 110 from skin body molding die 300. Then, the worker can complete golf ball 100 by subjecting skin body 110 to predetermined post-processing steps, such as a process of removing unnecessary portions corresponding to sprue portions 330a and 330b, a polishing process, a decorating process, and a cleaning process. In this embodiment, the worker can manufacture golf ball 100 weighing 75 g. This process of molding skin body 110 corresponds to the skin body molding process according to the present invention.

[0047] (Operation of golf ball 100) Next, the operation of golf ball 100 configured as described above will be described. A user of golf ball 100 prepares golf ball 100 along with a golf club when playing ground golf or park golf. After placing golf ball 100 on the playground, the user can play the game by hitting it with the golf club.

[0048] In this case, golf ball 100 is formed to be extremely light, weighing only 75 g, and has thin skin 110, which reduces the impact on the user when hit with a golf club and makes the ball more likely to stop after being hit. Also, in golf ball 100, outermost surface layer 103 of core sphere 101 is made of a translucent solid body, which hides air bubbles 102 from the outside, improving the aesthetic appearance of golf ball 100.

[0049] As can be seen from the above description of operation, according to the above embodiment, golf ball 100 has skin body 110 formed to a thickness of 4 mm or less, and core sphere 101 in contact with the inner surface of skin body 110 is entirely made of a resin material having a bending rigidity of 320 MPa or more. Therefore, even if golf ball 100 is made lighter, deformation of core sphere 101 can be suppressed, and golf ball 100 as a whole can be molded with high precision in terms of performance and aesthetics.

[0050] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention. In the following modifications, the same components as those in the above-described embodiment are designated by the same reference numerals, and their description will be omitted.

[0051] For example, in the above embodiment, the entire core sphere 101 is integrally formed into a solid sphere using the same resin material. In this case, the core sphere 101 is made of a resin material with a bending rigidity of 320 MPa. However, it is sufficient that the surface layer of the core sphere 101 in contact with the inner surface of the skin body 110 is made of a resin material with a bending rigidity of at least 300 MPa. According to experiments conducted by the present inventors, the bending rigidity of the core sphere 101 is preferably 320 MPa or more.

[0052] For example, as shown in FIG. 5, the core sphere 120 can have a two-layer structure consisting of a surface layer 121 formed in a hollow spherical shape inside the skin 110 and an inner layer 122 formed in a spherical shape inside the surface layer 121. In this case, the surface layer 121 and the inner layer 122 of the core sphere 120 can be formed separately from each other using the same or different resin materials. Furthermore, at least one of the surface layer 121 and the inner layer 122 of the core sphere 120 can be formed from a foamed resin material. In these cases, the surface layer 121 is preferably formed to a thickness of at least 4 mm using a resin material with a bending rigidity of at least 300 MPa. Furthermore, the surface layer 121 and the inner layer 122 may each be formed from a single sphere, or each may be formed by combining two hemispherical parts.

[0053] Furthermore, as shown in FIG. 6, the core sphere 130 can be configured as a hollow sphere with a hollow interior. That is, the core sphere 130 can have an internal space 131 formed therein, which is a space centered at the center of the core sphere 130. In this case, the internal space 131 can be formed in a spherical shape or a shape other than a sphere. However, by forming the internal space 131 as a space centered at the center of the core sphere 130, that is, a shape that is symmetrical vertically and horizontally, the center of gravity of the core sphere 130 can be the center of the core sphere 130. Even in this case, it is preferable that the thickness of the surface layer 132 of the core sphere 130 that contacts the inner surface of the skin body 110 is at least 4 mm or more. In this case, the core sphere 130 can be formed by combining two hemispherical parts.

[0054] Furthermore, as shown in Figure 7, the core sphere 130 can also be provided with an internal support 133 within the internal space 131. The internal support 133 is a component that is disposed within the internal space 131 to support the core sphere 130, and is provided in a state in which it is bridged within the internal space 131. In other words, the internal support 133 is provided fixedly within the internal space 131. In Figure 7, this internal support 133 is formed into a three-dimensional shape in which a semicircular plate-like body protrudes in the up, down, left, and right directions when viewed from the front, but it can be formed into any three-dimensional shape.

[0055] Furthermore, internal support 133 can be made of a metal material or wood in addition to a resin material. This allows golf ball 100 to be made lighter while effectively suppressing deformation of core sphere 130, thereby enabling the entire golf ball to be molded with precision in terms of both performance and aesthetics. Note that internal support 133 can be made of a fluid such as water or oil, instead of a resin material, metal material, or wood, and can be filled into internal space 131.

[0056] In the above embodiment, core sphere 101 has a weight of 35 g. This allows the worker to easily mold golf ball 100 weighing 85 g or less, particularly in the range of 75 g to 80 g, while maintaining its aesthetic appearance. However, by forming core sphere 101 to have a weight of 35 g to 55 g, it is possible to easily mold lightweight golf ball 100 weighing 85 g or less, particularly in the range of 75 g to 80 g, while maintaining its aesthetic appearance. Of course, core spheres 101, 120, and 130 may be made of a resin material without the addition of a foaming agent.

[0057] In the above embodiment, golf ball 100 has a weight of 75 g. This allows golf ball 100 to reduce the impact on the user when hit with a golf club and allows the ball to stop easily after being hit. In this case, golf ball 100 rolls easily, particularly on turf, increasing the flight distance, and the resistance of the turf makes it easier to stop, improving controllability. However, golf ball 100 can achieve the same effects by weighing 75 g or more and 80 g or less.

[0058] Furthermore, in the above embodiment, core sphere 101 is configured so that the size of air bubbles 102 increases toward the center. This allows golf ball 100 to be molded accurately in terms of performance and aesthetics while effectively suppressing deformation of core sphere 101 and reducing the weight of golf ball 100. Furthermore, golf ball 100 can be made lighter while preventing air bubbles 102 in inner layer 104 from being noticeable in appearance. However, core sphere 101 is configured so that the size of air bubbles 102 remains constant toward the center.

[0059] Furthermore, in the above embodiment, outermost surface layer 103 is formed from a portion extending up to 1 mm from the surface of core sphere 101. This allows golf ball 100 to be lightweight while effectively suppressing deformation of core sphere 101, thereby enabling the entire golf ball 100 to be molded with precision in terms of both performance and appearance. Furthermore, because golf ball 100 has outermost surface layer 103 formed from a solid body, air bubbles 102 in inner layer 104 are prevented from appearing on the exterior, improving the appearance of golf ball 100. However, outermost surface layer 103 may be formed from a solid body from a portion extending at least up to 1 mm from the surface of core sphere 101. In this case, outermost surface layer 103 preferably has a depth of 1 mm or more and 3 mm or less from the surface of core sphere 101. [Explanation of symbols]

[0060] 100...golf balls, 101...core sphere, 102...air bubbles, 103...outermost surface layer, 104...inner layer, 110...epidermal body, 120...Core sphere, 121...Surface layer, 122...Inner layer, 130... core sphere, 131... internal space, 132... surface layer, 133... internal support, 200...core sphere molding die, 210...first die, 211...first molding section, 220...second die, 221...second molding section, 230a, 230b...sprue section, 240...injection unit, 300...skin body molding die, 310...first die, 311...first molding section, 320...second die, 321...second molding section, 330a, 330b...sprue section, 340a, 340b...support pin, 350...injection unit.

Claims

1. A golf ball for ground golf or park golf, A core sphere made of ionomer resin, a skin made of an ionomer resin that covers the outer surface of the core spherical body and constitutes the outer surface of the golf ball, The epidermal body It is formed to a thickness of 4 mm or less, The core sphere is a surface layer in contact with the inner surface of the skin body is made of a resin material having a bending rigidity of at least 300 MPa, and an outermost layer at a depth of at least 1 mm from the surface in contact with the inner surface of the skin body is made of a solid body having no air bubbles; an inner layer located inside the outermost layer is made of a porous material having countless bubbles; The golf ball is characterized in that the outermost surface layer and the inner layer are integrally formed.

2. 2. The golf ball according to claim 1, The inner layer is A golf ball characterized in that the size of the air bubbles increases toward the center.

3. The golf ball according to claim 1 or 2, The core sphere is A golf ball formed to have a weight of 35 g or more and 55 g or less.

4. A method for manufacturing a golf ball for ground golf or park golf, comprising: a core sphere molding step of molding a core sphere made of an ionomer resin sphere; a skin molding step of molding a skin made of an ionomer resin that covers the outer surface of the core spherical body and constitutes the outer surface of the golf ball, The core sphere molding step includes: a foamed resin material having a bending rigidity of at least 300 MPa or more is injected into a mold at a temperature of 10°C or more and 50°C or less to form a surface layer in contact with the inner surface of the skin body, and the outermost surface layer having a depth of at least 1 mm from the surface in contact with the inner surface of the skin body is formed as a solid body having no bubbles, and an inner layer inside the outermost surface layer is formed as a porous body having countless bubbles, and the outermost surface layer and the inner layer are integrally molded; The skin forming step includes: A method for manufacturing a golf ball, comprising forming the skin body to a thickness of 4 mm or less.

5. 5. The method for manufacturing a golf ball according to claim 4, The core sphere molding step includes: The method for manufacturing a golf ball is characterized in that the core spherical body is formed to have a weight of 35 g or more and 55 g or less.

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