Patent Application
20180056136
This application claims priority on Patent Application No. 2016-166387 filed in JAPAN on Aug. 29, 2016. The entire contents of this Japanese Patent Application are hereby incorporated by reference.
The present invention relates to golf balls. Specifically, the present invention relates to golf balls having dimples on the surfaces thereof.
Golf balls have a large number of dimples on the surfaces thereof. The dimples disturb the air flow around the golf ball during flight to cause turbulent flow separation. This phenomenon is referred to as “turbulization”. Due to the turbulization, separation points of the air from the golf ball shift backwards leading to a reduction of drag. The turbulization promotes the displacement between the separation point on the upper side and the separation point on the lower side of the golf ball, which results from the backspin, thereby enhancing the lift force that acts upon the golf ball. The reduction of drag and the enhancement of lift force are referred to as a “dimple effect”. Excellent dimples efficiently disturb the air flow. The excellent dimples produce a long flight distance.
JP2015-142599 (US2015/0182805) discloses a golf ball having a surface with large roughness. The roughness can be formed by blasting or the like. The roughness enhances the aerodynamic characteristic of the golf ball due to a synergetic effect with dimples.
JP2011-72776 (US2011/0077106) discloses a golf ball having a coating formed from a paint that contains particles. The particles enhance the aerodynamic characteristic of the golf ball due to a synergetic effect with dimples.
JPH2-68077 discloses a golf ball having dimples each having one projection at a bottom thereof. The dimples each having the projection enhance the aerodynamic characteristic of the golf ball.
The greatest interest to golf players concerning golf balls is flight distance. Golf players desire golf balls having excellent flight performance. Golf players having an average skill desire golf balls having excellent flight performance particularly when being hit with a long iron.
An object of the present invention is to provide a golf ball having excellent flight performance when being hit with a long iron.
A golf ball according to the present invention has a plurality of dimples and a land. The golf ball further has a large number of minute projections formed on surfaces of the dimples and/or the land. An average depth Fav of the dimples and an average height Hav of the minute projections satisfy the following mathematical formula (1).
Hav<Fav*0.05 (1)
With the golf ball according to the present invention, the minute projections suppress rising of the golf ball during flight. With the golf ball, a large flight distance can be achieved due to a synergetic effect of the dimples and the minute projections.
Preferably, an average value Pav of pitches P between the minute projections and other minute projections adjacent to the minute projections is not less than 10 μm and not greater than 2000 μm.
The golf ball can have a plurality of rows. Preferably, in each of the rows, a plurality of minute projections are aligned at equal pitches.
Preferably, an average area Sav of the dimples and an average area Qav of bottom surfaces of the minute projections satisfy the following mathematical formula (2).
Qav<Sav*0.016 (2)
The golf ball can include a main body and a paint layer positioned outside the main body. Preferably, the minute projections each have a shape in which a surface shape of the main body is reflected.
Preferably, an average value Lav of distances between the minute projections and other minute projections adjacent to the minute projections is not less than 5 μm and not greater than 1500 μm.
Preferably, the average height Hav of the minute projections is not less than 0.5 μm and not greater than 25 μm.
Preferably, a total number of the minute projections is not less than 500 and not greater than 500000.
The following will describe in detail the present invention based on preferred embodiments with appropriate reference to the drawings.
A golf ball 2 shown in
The golf ball 2 preferably has a diameter of not less than 40 mm and not greater than 45 mm. From the standpoint of conformity to the rules established by the United States Golf Association (USGA), the diameter is particularly preferably not less than 42.67 mm. In light of suppression of air resistance, the diameter is more preferably not greater than 44 mm and particularly preferably not greater than 42.80 mm. The diameter of the golf ball 2 according to the present embodiment is 42.7 mm.
The golf ball 2 preferably has a weight of not less than 40 g and not greater than 50 g. In light of attainment of great inertia, the weight is more preferably not less than 44 g and particularly preferably not less than 45.00 g. From the standpoint of conformity to the rules established by the USGA, the weight is particularly preferably not greater than 45.93 g.
The core 4 is formed by crosslinking a rubber composition. Examples of the base rubber of the rubber composition include polybutadienes, polyisoprenes, styrene-butadiene copolymers, ethylene-propylene-diene copolymers, and natural rubbers. Two or more rubbers may be used in combination. In light of resilience performance, polybutadienes are preferable, and high-cis polybutadienes are particularly preferable.
The rubber composition of the core 4 includes a co-crosslinking agent. Examples of preferable co-crosslinking agents in light of resilience performance include zinc acrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate. The rubber composition preferably includes an organic peroxide together with a co-crosslinking agent. Examples of preferable organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide.
The rubber composition of the core 4 may include additives such as a filler, sulfur, a vulcanization accelerator, a sulfur compound, an anti-aging agent, a coloring agent, a plasticizer, and a dispersant. The rubber composition may include a carboxylic acid or a carboxylate. The rubber composition may include synthetic resin powder or crosslinked rubber powder.
The core 4 has a diameter of preferably not less than 30.0 mm and particularly preferably not less than 38.0 mm. The diameter of the core 4 is preferably not greater than 42.0 mm and particularly preferably not greater than 41.5 mm. The core 4 may have two or more layers. The core 4 may have a rib on the surface thereof. The core 4 may be hollow.
The mid layer 6 is formed from a resin composition. preferable base polymer of the resin composition is an ionomer resin. Examples of preferable ionomer resins include binary copolymers formed with an α-olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Examples of other preferable ionomer resins include ternary copolymers formed with: an α-olefin; an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; and an α,β-unsaturated carboxylate ester having 2 to 22 carbon atoms. For the binary copolymer and the ternary copolymer, preferable α-olefins are ethylene and propylene, while preferable α,β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In the binary copolymer and the ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of metal ions for use in neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion, and neodymium ion.
Instead of an ionomer resin, the resin composition of the mid layer 6 may include another polymer. Examples of the other polymer include polystyrenes, polyamides, polyesters, polyolefins, and polyurethanes. The resin composition may include two or more polymers.
The resin composition of the mid layer 6 may include a coloring agent such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like. For the purpose of adjusting specific gravity, the resin composition may include powder of a metal with a high specific gravity such as tungsten, molybdenum, and the like.
The mid layer 6 has a thickness of preferably not less than 0.2 mm and particularly preferably not less than 0.3 mm. The thickness of the mid layer 6 is preferably not greater than 2.5 mm and particularly preferably not greater than 2.2 mm. The mid layer 6 has a specific gravity of preferably not less than 0.90 and particularly preferably not less than 0.95. The specific gravity of the mid layer 6 is preferably not greater than 1.10 and particularly preferably not greater than 1.05. The mid layer 6 may have two or more layers.
The cover 8 is formed from a resin composition. A preferable base polymer of the resin composition is a polyurethane. The resin composition may include a thermoplastic polyurethane or may include a thermosetting polyurethane. In light of productivity, the thermoplastic polyurethane is preferable. The thermoplastic polyurethane includes a polyurethane component as a hard segment, and a polyester component or a polyether component as a soft segment.
The polyurethane has a urethane bond within the molecule. The urethane bond can be formed by reacting a polyol with a polyisocyanate.
The polyol, which is a material for the urethane bond, has a plurality of hydroxyl groups. Low-molecular-weight polyols and high-molecular-weight polyols can be used.
Examples of an isocyanate for the polyurethane component include alicyclic diisocyanates, aromatic diisocyanates, and aliphatic diisocyanates. Alicyclic diisocyanates are particularly preferable. Since an alicyclic diisocyanate does not have any double bond in the main chain, the alicyclic diisocyanate suppresses yellowing of the cover 8. Examples of alicyclic diisocyanates include 4,4′-dicyclohexylmethane diisocyanate (H12MDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane diisocyanate (CHDI). In light of versatility and processability, H12MDI is preferable.
Instead of a polyurethane, the resin composition of the cover 8 may include another polymer. Examples of the other polymer include ionomer resins, polystyrenes, polyamides, polyesters, and polyolefins. The resin composition may include two or more polymers.
The resin composition of the cover 8 may include a coloring agent such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like.
The cover 8 has a thickness of preferably not less than 0.2 mm and particularly preferably not less than 0.3 mm. The thickness of the cover 8 is preferably not greater than 2.5 mm and particularly preferably not greater than 2.2 mm. The cover 8 has a specific gravity of preferably not less than 0.90 and particularly preferably not less than 0.95. The specific gravity of the cover 8 is preferably not greater than 1.10 and particularly preferably not greater than 1.05. The cover 8 may have two or more layers.
The golf ball 2 may include a reinforcing layer between the mid layer 6 and the cover 8. The reinforcing layer firmly adheres to the mid layer 6 and also to the cover 8. The reinforcing layer suppresses separation of the cover 8 from the mid layer 6. The reinforcing layer is formed from a polymer composition. Examples of the base polymer of the reinforcing layer include two-component curing type epoxy resins and two-component curing type urethane resins.
The golf ball 2 has type I dimple specifications shown in Table 1 below. The contour of each dimple 12 is circular. The golf ball 2 has: dimples A each having a diameter of 4.60 mm; dimples B each having a diameter of 4.50 mm; dimples C each having a diameter of 4.30 mm; dimples D each having a diameter of 4.20 mm; dimples E each having a diameter of 4.00 mm; and dimples F each having a diameter of 2.90 mm. The number of kinds of the dimples 12 is six. The golf ball 2 may have non-circular dimples instead of the circular dimples 12 or together with circular dimples 12.
The number of the dimples A is 72; the number of the dimples B is 54; the number of the dimples C is 30; the number of dimples D is 54; the number of the dimples E is 108; and the number of the dimples F is 12. The total number of the dimples 12 is 330. A dimple pattern is formed by these dimples 12 and the land 14.
In
The diameter Dm of each dimple 12 is preferably not less than 2.0 mm and not greater than 6.0 mm. The dimple 12 having a diameter Dm of not less than 2.0 mm contributes to turbulization. In this respect, the diameter Dm is more preferably not less than 2.5 mm and particularly preferably not less than 2.8 mm. The dimple 12 having a diameter Dm of not greater than 6.0 mm does not impair a fundamental feature of the golf ball 2 being substantially a sphere. In this respect, the diameter Dm is more preferably not greater than 5.5 mm and particularly preferably not greater than 5.0 mm.
In the case of a non-circular dimple, a circular dimple 12 having the same area as that of the non-circular dimple is assumed. The diameter of the assumed dimple 12 can be regarded as the diameter of the non-circular dimple.
In
The area S of the dimple 12 is the area of a region surrounded by the contour line of the dimple 12 when the central point of the golf ball 2 is viewed at infinity. In the case of a circular dimple 12, the area S is calculated by the following mathematical formula.
S=(Dm/2)2*π
An average area Sav is calculated by summing the areas S of all the dimples 12 and dividing the sum of the areas S by the number of the dimples 12.
In the golf ball 2 according to the present embodiment, the area of each dimple A is 16.62 mm2; the area of each dimple B is 15.90 mm2; the area of each dimples C is 14.52 mm2; the area of each dimple D is 13.85 mm2; the area of each dimple E is 12.57 mm2; and the area of each dimple F is 6.61 mm2. The average area Sav of the golf ball 2 is 14.17 mm2.
In the present invention, the ratio of the sum of the areas S of all the dimples 12 relative to the surface area of the phantom sphere 16 is referred to as an occupation ratio So. From the standpoint that sufficient turbulization is achieved, the occupation ratio So is preferably not less than 78.0%, more preferably not less than 80.0%, and particularly preferably not less than 81.0%. The occupation ratio So is preferably not greater than 95%. In the golf ball 2 according to the present embodiment, the total area of the dimples 12 is 4675.6 mm2. The surface area of the phantom sphere 16 of the golf ball 2 is 5728.0 mm2, so that the occupation ratio So is 81.6%.
From the standpoint that a sufficient occupation ratio is achieved, the total number N of the dimples 12 is preferably not less than 250, more preferably not less than 280, and particularly preferably not less than 300. From the standpoint that each dimple 12 can contribute to turbulization, the total number N of the dimples 10 is preferably not greater than 450, more preferably not greater than 400, and particularly preferably not greater than 380.
In the present invention, the “volume of the dimple” means the volume of a portion surrounded by the surface of the phantom sphere 16 and the surface of the dimple 12. In light of suppression of rising of the golf ball 2 during flight, the total volume of all the dimples 12 is preferably not less than 450 mm3, more preferably not less than 480 mm3, and particularly preferably not less than 500 mm3. In light of suppression of dropping of the golf ball 2 during flight, the total volume is preferably not greater than 750 mm3, more preferably not greater than 730 mm3, and particularly preferably not greater than 710 mm3.
The minute projections 18a, which belong to the first row I, and the minute projections 18b, which belong to the second row II, may be arranged zigzag. In other words, the positions of the minute projections 18a, which belong to the first row I, may be displaced relative to the positions of the minute projections 18b, which belong to the second row II, in the extending direction A.
In
For each minute projection 18, one pitch P is determined. An average pitch Pav is calculated by summing the pitches P of all the minute projections 18 and dividing the sum of the pitches P by the number of the minute projections 18. The average pitch Pav is preferably not less than 10 μm and not greater than 2000 μm. With the golf ball 2 in which the average pitch Pav falls within this range, the minute projections 18 suppress rising of the golf ball 2 during flight. In this respect, the average pitch Pav is more preferably not less than 20 μm and particularly preferably not less than 30 μm. The average pitch Pav is more preferably not greater than 1500 μm and particularly preferably not greater than 1000 μm.
In
In
In the golf ball 2, the average depth Fav of the dimples 12 and the average height Hav of the minute projections 18 satisfy the following mathematical formula (1).
Hav<Fav*0.05 (1)
In other words, the average height Hav is less than (Fav*0.05). With the golf ball 2, the minute projections 18 do not impair the dimple effect. With the golf ball 2, sufficient lift force can be obtained. In this respect, the average height Hav is more preferably not greater than (Fav*0.04) and particularly preferably not greater than (Fav*0.03). From the standpoint that the minute projections 18 suppress rising of the golf ball 2 during flight, the average height Hav is preferably not less than (Fav*0.005), more preferably not less than (Fav*0.008), and particularly preferably not less than (Fav*0.010).
An average area Qav is calculated by summing the areas Q of the bottom surfaces 24 of all the minute projections 18 and dividing the sum of the areas Q by the number of the minute projections 18. From the standpoint that the minute projections 18 suppress rising of the golf ball 2 during flight, the average area Qav is preferably not less than 10 μm2, more preferably not less than 100 μm2, and particularly preferably not less than 500 μm2. From the standpoint that the minute projections 18 do not impair the dimple effect, the average area Qav is preferably not greater than 4000000 μm2, more preferably not greater than 1000000 μm2, and particularly preferably not greater than 300000 μm2.
From the standpoint that the minute projections 18 suppress rising of the golf ball 2 during flight, the ratio of the sum of the areas Q of the bottom surfaces 24 of all the minute projections 18 relative to the surface area of the phantom sphere 16 is preferably not less than 5%, more preferably not less than 15%, and particularly preferably not less than 20%. From the standpoint that the minute projections 18 do not impair the dimple effect, the ratio is preferably not greater than 80%, more preferably not greater than 60%, and particularly preferably not greater than 50%.
From the standpoint that the minute projections 18 suppress rising of the golf ball 2 during flight, the total number of the minute projections 18 is preferably not less than 500, more preferably not less than 1000, and particularly preferably not less than 2000. From the standpoint that the minute projections 18 do not impair the dimple effect, the total number is preferably not greater than 500000, more preferably not greater than 300000, and particularly preferably not greater than 100000.
Preferably, the average area Sav of the dimples 12 and the average area Qav of the bottom surfaces 24 of the minute projections 18 satisfy the following mathematical formula (2).
Qav<Sav*0.016 (2)
In other words, the average area Qav of the bottom surfaces 24 of the minute projections 18 is less than (Sav*0.016). With the golf ball 2, the minute projections 18 do not impair the dimple effect. With the golf ball 2, sufficient lift force can be obtained. In this respect, the average area Qav is more preferably not greater than (Sav*0.010) and particularly preferably not greater than (Sav*0.005). From the standpoint that the minute projections 18 suppress rising of the golf ball 2 during flight, the average area Qav is preferably not less than (Sav*0.000001), more preferably not less than (Sav*0.00001), and particularly preferably not less than (Sav*0.00003).
As described above, each minute projection 18 includes the projection portion 22 of the main body 10 and the paint layer 20 (see
The projection portions 22 of the main body 10 are formed simultaneously with formation of the main body 10. For the formation, a mold is used. The cavity face of the mold has a large number of minute recesses. Each recess has a shape that is substantially the inverted shape of the projection portion 22. The mold can be obtained from a master mold. One example of a method for producing the master mold is etching. During etching, a large number of minute maskings are used. By the maskings, projection portions are formed on the master mold. By the projection portions of the master mold, recesses are formed on the mold. The positions of the maskings correspond to the positions of the projection portions of the master mold, correspond to the positions of the recesses of the mold, and correspond to the positions of the minute projections 18 of the golf ball 2. The master mold can be produced by various methods other than etching. Examples of a method other than etching include laser radiation processing.
As described above, the minute projections 18 are formed on the surfaces of the dimples 12 and also on the surface of the land 14 (see
The shape of each minute projection 18 shown in
A rubber composition was obtained by kneading 100 parts by weight of a high-cis polybutadiene (trade name “BR-730”, manufactured by JSR Corporation), 35 parts by weight of zinc diacrylate, 5 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide, 0.9 parts by weight of dicumyl peroxide, and 2 parts by weight of zinc octoate. This rubber composition was placed into a mold including upper and lower mold halves each having a hemispherical cavity, and heated at 160° C. for 20 minutes to obtain a core with a diameter of 39.7 mm. The amount of barium sulfate was adjusted such that a core having a predetermined weight was obtained.
A resin composition was obtained by kneading 50 parts by weight of an ionomer resin (trade name “Himilan 1605”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 50 parts by weight of another ionomer resin (trade name “Himilan AM7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of ultramarine blue with a twin-screw kneading extruder. The core was covered with this resin composition by injection molding to form a mid layer with a thickness of 1.0 mm.
A paint composition (trade name “POLIN 750LE”, manufactured by SHINTO PAINT CO., LTD.) including a two-component curing type epoxy resin as a base polymer was prepared. The base material liquid of this paint composition includes 30 parts by weight of a bisphenol A type solid epoxy resin and 70 parts by weight of a solvent. The curing agent liquid of this paint composition includes 40 parts by weight of a modified polyamide amine, 55 parts by weight of a solvent, and 5 parts by weight of titanium dioxide. The weight ratio of the base material liquid to the curing agent liquid is 1/1. This paint composition was applied to the surface of the mid layer with a spray gun, and kept at 23° C. for 6 hours to obtain a reinforcing layer with a thickness of 10 μm.
A resin composition was obtained by kneading 100 parts by weight of a thermoplastic polyurethane elastomer (trade name “Elastollan XNY85A”, manufactured by BASF Japan Ltd.) and 4 parts by weight of titanium dioxide with a twin-screw kneading extruder. Half shells were obtained from this resin composition by compression molding. The sphere consisting of the core, the mid layer, and the reinforcing layer was covered with two of these half shells. These half shells and the sphere were placed into a final mold that includes upper and lower mold halves each having a hemispherical cavity and having a large number of pimples and minute recesses on its cavity face, and a cover was obtained by compression molding. The thickness of the cover was 0.5 mm. Dimples having a shape that is the inverted shape of the pimples were formed on the cover. Furthermore, minute projection portions having a shape that is the inverted shape of the minute recesses were formed on the cover.
A clear paint including a two-component curing type polyurethane as a base material was applied to this cover to obtain a golf ball of Example 1 with a diameter of about 42.7 mm and a weight of about 45.6 g. The golf ball has a large number of minute projections on the surface thereof. The specifications of these minute projections are shown in Table 1 below.
Golf balls of Examples 2 to 7 and Comparative Example 1 were obtained in the same manner as Example 1, except the final mold was changed and minute projections having specifications shown in Tables 2 and 3 below were formed.
A golf ball of Comparative Example 2 was obtained in the same manner as Example 1, except the final mold was changed and a cover having no projection portion was molded.
Golf balls of Examples 8 to 10 and Comparative Example 3 were obtained in the same manner as Example 1, except the final mold was changed and dimples and minute projections having specifications shown in Table 4 below were formed.
A golf ball of Comparative Example 4 was obtained in the same manner as Example 1, except the final mold was changed, dimples having specifications shown in Table 4 below were formed, and a cover having no projection portion was molded.
[Flight Test]
A 5-iron (trade name “SRIXON Z725”, manufactured by DUNLOP SPORTS CO. LTD., shaft hardness: S, loft angle: 25.0°) was attached to a swing machine manufactured by Golf Laboratories, Inc. A golf ball was hit under a condition of a head speed of 41 m/sec, and the distance from the launch point to the landing point was measured. At the test, the weather was almost windless. The average value of data obtained from 20 measurements is shown in Tables 2 to 4 below.
As shown in Tables 2 to 4, the golf ball of each Example has excellent flight performance with a long iron. From the results of evaluation, advantages of the present invention are clear.
The aforementioned minute projections are applicable to golf balls having various structures such as a one-piece golf ball, a two-piece golf ball, a four-piece golf ball, a five-piece golf ball, a six-piece golf ball, a thread-wound golf ball, and the like in addition to a three-piece golf ball. The above descriptions are merely illustrative examples, and various modifications can be made without departing from the principles of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-166387 | Aug 2016 | JP | national |
