U.S. patent application number 14/788311 was filed with the patent office on 2015-12-31 for golf ball.
This patent application is currently assigned to DUNLOP SPORTS CO. LTD.. The applicant listed for this patent is DUNLOP SPORTS CO. LTD.. Invention is credited to Kohei MIMURA, Takahiro SAJIMA.
Application Number | 20150375053 14/788311 |
Document ID | / |
Family ID | 54929428 |
Filed Date | 2015-12-31 |
United States Patent
Application |
20150375053 |
Kind Code |
A1 |
MIMURA; Kohei ; et
al. |
December 31, 2015 |
GOLF BALL
Abstract
A golf ball 2 includes a center 8, a mid layer 10, a cover 6 and
dimples 12. The cover 6 has a Shore D hardness of 30-50. The golf
ball 2 has an amount of compressive deformation of 3.0-5.0 mm. The
ball 2 meets a mathematical formula (I):
0.80.ltoreq.((L1+L2)/2).ltoreq.0.95 (I). L1 represents a ratio of a
lift coefficient CL1 relative to a drag coefficient CD1, the lift
coefficient CL1 and the drag coefficient CD1 being measured under
conditions of a Reynolds number of 1.290.times.10.sup.5 and a spin
rate of 2820 rpm. L2 represents a ratio of a lift coefficient CL2
relative to a drag coefficient CD2, the lift coefficient CL2 and
the drag coefficient CD2 being measured under conditions of a
Reynolds number of 1.771.times.10.sup.5 and a spin rate of 2940
rpm.
Inventors: |
MIMURA; Kohei; (Kobe-shi,
JP) ; SAJIMA; Takahiro; (Kobe-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DUNLOP SPORTS CO. LTD. |
Kobe-shi |
|
JP |
|
|
Assignee: |
DUNLOP SPORTS CO. LTD.
Kobe-shi
JP
|
Family ID: |
54929428 |
Appl. No.: |
14/788311 |
Filed: |
June 30, 2015 |
Current U.S.
Class: |
473/377 |
Current CPC
Class: |
A63B 37/0074 20130101;
A63B 37/0087 20130101; A63B 37/0021 20130101; A63B 37/0019
20130101; A63B 37/0096 20130101; A63B 37/0018 20130101; A63B
37/0033 20130101; A63B 37/0017 20130101; A63B 37/002 20130101; A63B
37/0089 20130101; A63B 37/009 20130101; A63B 37/0031 20130101 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2014 |
JP |
2014-133826 |
Claims
1. A golf ball comprising a core and a cover positioned outside the
core, wherein the golf ball has a large number of dimples on a
surface thereof, the cover has a Shore D hardness of equal to or
greater than 30 but equal to or less than 50, the golf ball has an
amount of compressive deformation of equal to or greater than 3.0
mm but equal to or less than 5.0 mm, the amount of compressive
deformation being measured under conditions of an initial load of
98 N and a final load of 1274 N, and the golf ball meets the
following mathematical formula (I):
0.80.ltoreq.((L1+L2)/2).ltoreq.0.95 (I), where: L1 represents a
ratio (CL1/CD1) of a lift coefficient CL1 relative to a drag
coefficient CD1, the lift coefficient CL1 and the drag coefficient
CD1 being measured under conditions of a Reynolds number of
1.290.times.10.sup.5 and a spin rate of 2820 rpm; and L2 represents
a ratio (CL2/CD2) of a lift coefficient CL2 relative to a drag
coefficient CD2, the lift coefficient CL2 and the drag coefficient
CD2 being measured under conditions of a Reynolds number of
1.771.times.10.sup.5 and a spin rate of 2940 rpm.
2. The golf ball according to claim 1, wherein a total volume of
the dimples is equal to or greater than 430 mm.sup.3 but equal to
or less than 580 mm.sup.3.
3. The golf ball according to claim 1, wherein the cover has a
thickness of equal to or greater than 0.3 mm but equal to or less
than 1.8 mm.
4. The golf ball according to claim 1, wherein the ratio L1 is
equal to or greater than 0.85 but equal to or less than 0.93.
5. The golf ball according to claim 1, wherein the ratio L2 is
equal to or greater than 0.76 but equal to or less than 0.92.
6. The golf ball according to claim 1, wherein a ratio of a sum of
spherical surface areas of the dimples relative to a surface area
of a phantom sphere of the golf ball is equal to or greater than
0.780 but equal to or less than 0.950.
7. The golf ball according to claim 1, wherein a total number of
the dimples is equal to or greater than 250 but equal to or less
than 450.
8. The golf ball according to claim 1, wherein each dimple has a
diameter Dm of equal to or greater than 2.0 mm but equal to or less
than 6.0 mm.
9. The golf ball according to claim 1, wherein each dimple has a
depth of equal to or greater than 0.10 mm but equal to or less than
0.60 mm.
Description
[0001] This application claims priority on Patent Application No.
2014-133826 filed in JAPAN on Jun. 30, 2014. The entire contents of
this Japanese Patent Application are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to golf balls. Specifically,
the present invention relates to improvement of aerodynamic
characteristics of golf balls.
[0004] 2. Description of the Related Art
[0005] 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. Excellent dimples efficiently disturb the air flow.
The excellent dimples produce a long flight distance.
[0006] A golf player can select the brand of a golf ball to be used
by the golf player. In a golf tournament, the brand of a golf ball
used by a golf player is often different from that of another golf
player. In this respect, golf is a unique ball game.
[0007] Golf should be a sport in which golf players compete with
each other on their skills. It is not preferable that scores of
golf players greatly depend on the brands of golf balls. In this
respect, the United States Golf Association (USGA) has established
various rules about characteristics of golf balls. For example,
rules about weight, diameter, initial speed, flight distance, and
symmetry have been established.
[0008] Various golf balls have been proposed which can satisfy golf
players while conforming to the rules.
[0009] JPH5-103846 discloses a golf ball which has dimples the
diameters, the depths, and the number of which are made
appropriate.
[0010] U.S. Pat. No. 5,782,703 (JPH10-43342) discloses a golf ball
which has dimples the ratio of the diameter and the depth of each
of which is made appropriate.
[0011] U.S. Pat. No. 5,782,702 (JPH10-43343) discloses a golf ball
in which the ratio of the volumes of dimples relative to the volume
of the ball is made appropriate.
[0012] JP2000-107338 discloses a golf ball having a diameter and a
weight which are made appropriate.
[0013] Technological innovation in golf ball and golf club is
remarkable. In recent tour tournaments, the average flight distance
at tee shots has been increasing. The large flight distance makes a
second shot easy. The large flight distance impairs the public
interest in tournaments.
[0014] The USGA is scheduled to change the rules about flight
distance. The head speeds of professional golf players who
participate in tournaments are high. The USGA will strengthen
regulations on a flight distance upon hitting at a high head
speed.
[0015] Meanwhile, there are no regulations on a flight distance
upon hitting at a low head speed. Amateur golf players desire
longer flight distances. A golf ball is desired which achieves a
long flight distance when being hit at a low head speed while
conforming to the rules of the USGA.
[0016] For golf players, in addition to flight distance, feeling is
also important. Golf players place importance on hit feeling and
trajectory feeling. Golf players prefer soft hit feeling.
Furthermore, golf players prefer high trajectories.
[0017] An object of the present invention is to provide a golf ball
which satisfies a golf player having a low head speed.
SUMMARY OF THE INVENTION
[0018] A golf ball according to the present invention includes a
core and a cover positioned outside the core. The golf ball has a
large number of dimples on a surface thereof. The cover has a Shore
D hardness of equal to or greater than 30 but equal to or less than
50. The golf ball has an amount of compressive deformation of equal
to or greater than 3.0 mm but equal to or less than 5.0 mm, the
amount of compressive deformation being measured under conditions
of an initial load of 98 N and a final load of 1274 N. The golf
ball meets the following mathematical formula (I):
0.80.ltoreq.((L1+L2)/2).gtoreq.0.95 (I),
where: L1 represents a ratio (CL1/CD1) of a lift coefficient CL1
relative to a drag coefficient CD1, the lift coefficient CL1 and
the drag coefficient CD1 being measured under conditions of a
Reynolds number of 1.290.times.10.sup.5 and a spin rate of 2820
rpm; and L2 represents a ratio (CL2/CD2) of a lift coefficient CL2
relative to a drag coefficient CD2, the lift coefficient CL2 and
the drag coefficient CD2 being measured under conditions of a
Reynolds number of 1.771.times.10.sup.5 and a spin rate of 2940
rpm.
[0019] When the golf ball according to the present invention is hit
by a golf player having a low head speed, a sufficient flight
distance is achieved. The golf ball provides preferable feeling to
the golf player having a low head speed.
[0020] Preferably, a total volume of the dimples is equal to or
greater than 430 mm.sup.3 but equal to or less than 580
mm.sup.3.
[0021] Preferably, the cover has a thickness of equal to or greater
than 0.3 mm but equal to or less than 1.8 mm.
[0022] Preferably, the ratio L1 is equal to or greater than 0.85
but equal to or less than 0.93. Preferably, the ratio L2 is equal
to or greater than 0.76 but equal to or less than 0.92.
[0023] Preferably, a ratio of a sum of spherical surface areas of
the dimples relative to a surface area of a phantom sphere of the
golf ball is equal to or greater than 0.780 but equal to or less
than 0.950.
[0024] Preferably, a total number of the dimples is equal to or
greater than 250 but equal to or less than 450.
[0025] Preferably, each dimple has a diameter Dm of equal to or
greater than 2.0 mm but equal to or less than 6.0 mm.
[0026] Preferably, each dimple has a depth of equal to or greater
than 0.10 mm but equal to or less than 0.60 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a cross-sectional view of a golf ball according to
one embodiment of the present invention;
[0028] FIG. 2 is an enlarged front view of the golf ball in FIG.
1;
[0029] FIG. 3 is a plan view of the golf ball in FIG. 2; and
[0030] FIG. 4 is a partially enlarged cross-sectional view of the
golf ball in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] The following will describe in detail the present invention,
based on preferred embodiments with reference to the accompanying
drawings.
[0032] FIG. 1 is a partially cutaway cross-sectional view of a golf
ball 2 according to one embodiment of the present invention. The
golf ball 2 includes a spherical core 4 and a cover 6 positioned
outside the core 4. The core 4 includes a spherical center 8 and a
mid layer 10 positioned outside the center 8. The golf ball 2
includes a paint layer and a mark layer on the external side of the
cover 6 although these layers are not shown in the drawing.
Furthermore, the golf ball 2 has a large number of dimples 12 on
the surface thereof. Of the surface of the golf ball 2, the part
other than the dimples 12 is a land 14. The golf ball 2 may include
another layer between the center 8 and the mid layer 10. The golf
ball 2 may include another layer between the mid layer 10 and the
cover 6.
[0033] The golf ball 2 preferably has a diameter of equal to or
greater than 40 mm but equal to or less than 45 mm. From the
standpoint of conformity to the rules established by the United
States Golf Association (USGA), the diameter is particularly
preferably equal to or greater than 42.67 mm. In light of
suppression of air resistance, the diameter is more preferably
equal to or less than 44 mm and particularly preferably equal to or
less than 42.80 mm. The golf ball 2 preferably has a weight of
equal to or greater than 40 g but equal to or less than 50 g. In
light of attainment of great inertia, the weight is more preferably
equal to or greater than 44 g and particularly preferably equal to
or greater than 45.00 g. From the standpoint of conformity to the
rules established by the USGA, the weight is particularly
preferably equal to or less than 45.93 g.
[0034] The center 8 is obtained by crosslinking a rubber
composition. Examples of preferable base rubbers for use in the
rubber composition include polybutadienes, polyisoprenes,
styrene-butadiene copolymers, ethylene-propylene-diene copolymers,
and natural rubbers. In light of resilience performance,
polybutadienes are preferred. When a polybutadiene and another
rubber are used in combination, it is preferred if the
polybutadiene is a principal component. Specifically, the
proportion of the polybutadiene to the entire base rubber is
preferably equal to or greater than 50% by weight and particularly
preferably equal to or greater than 80% by weight. A polybutadiene
in which the proportion of cis-1,4 bonds is equal to or greater
than 80% is particularly preferred.
[0035] The rubber composition of the center 8 preferably includes a
co-crosslinking agent. Preferable co-crosslinking agents in light
of resilience performance are monovalent or bivalent metal salts of
an .alpha.,.beta.-unsaturated carboxylic acid having 2 to 8 carbon
atoms. Examples of preferable co-crosslinking agents include zinc
acrylate, magnesium acrylate, zinc methacrylate, and magnesium
methacrylate. In light of resilience performance, zinc acrylate and
zinc methacrylate are particularly preferred.
[0036] The rubber composition may include a metal oxide and an
.alpha.,.beta.-unsaturated carboxylic acid having 2 to 8 carbon
atoms. They both react with each other in the rubber composition to
obtain a salt. The salt serves as a co-crosslinking agent. Examples
of preferable .alpha.,.beta.-unsaturated carboxylic acids include
acrylic acid and methacrylic acid. Examples of preferable metal
oxides include zinc oxide and magnesium oxide.
[0037] In light of resilience performance of the golf ball 2, the
amount of the co-crosslinking agent per 100 parts by weight of the
base rubber is preferably equal to or greater than 10 parts by
weight and particularly preferably equal to or greater than 15
parts by weight. In light of soft feel at impact, the amount is
preferably equal to or less than 50 parts by weight and
particularly preferably equal to or less than 45 parts by
weight.
[0038] Preferably, the rubber composition of the center 8 includes
an organic peroxide together with the co-crosslinking agent. The
organic peroxide serves as a crosslinking initiator. The organic
peroxide contributes to the resilience performance of the golf ball
2. Examples of suitable 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.
An organic peroxide with particularly high versatility is dicumyl
peroxide.
[0039] In light of resilience performance of the golf ball 2, the
amount of the organic peroxide per 100 parts by weight of the base
rubber is preferably equal to or greater than 0.1 parts by weight,
more preferably equal to or greater than 0.3 parts by weight, and
particularly preferably equal to or greater than 0.5 parts by
weight. In light of soft feel at impact, the amount is preferably
equal to or less than 3.0 parts by weight, more preferably equal to
or less than 2.8 parts by weight, and particularly preferably equal
to or less than 2.5 parts by weight.
[0040] Preferably, the rubber composition of the center 8 includes
an organic sulfur compound. Examples of preferable organic sulfur
compounds include monosubstitutions such as diphenyl disulfide,
bis(4-chlorophenyl)disulfide, bis(3-chlorophenyl)disulfide,
bis(4-bromophenyl)disulfide, bis(3-bromophenyl)disulfide,
bis(4-fluorophenyl)disulfide, bis(4-iodophenyl)disulfide, and
bis(4-cyanophenyl)disulfide; disubstitutions such as
bis(2,5-dichlorophenyl)disulfide, bis(3,5-dichlorophenyl)disulfide,
bis(2,6-dichlorophenyl)disulfide, bis(2,5-dibromophenyl)disulfide,
bis(3,5-dibromophenyl)disulfide,
bis(2-chloro-5-bromophenyl)disulfide, and
bis(2-cyano-5-bromophenyl)disulfide; trisubstitutions such as
bis(2,4,6-trichlorophenyl)disulfide and
bis(2-cyano-4-chloro-6-bromophenyl)disulfide; tetrasubstitutions
such as bis(2,3,5,6-tetrachlorophenyl)disulfide; and
pentasubstitutions such as
bis(2,3,4,5,6-pentachlorophenyl)disulfide and
bis(2,3,4,5,6-pentabromophenyl)disulfide. The organic sulfur
compound contributes to resilience performance. Particularly
preferable organic sulfur compounds are diphenyl disulfide and
bis(pentabromophenyl)disulfide.
[0041] In light of resilience performance of the golf ball 2, the
amount of the organic sulfur compound per 100 parts by weight of
the base rubber is preferably equal to or greater than 0.1 parts by
weight and particularly preferably equal to or greater than 0.2
parts by weight. In light of soft feel at impact, the amount is
preferably equal to or less than 1.5 parts by weight, more
preferably equal to or less than 1.0 parts by weight, and
particularly preferably equal to or less than 0.8 parts by
weight.
[0042] For the purpose of adjusting specific gravity and the like,
a filler may be included in the center 8. Examples of suitable
fillers include zinc oxide, barium sulfate, calcium carbonate, and
magnesium carbonate. Powder of a metal with a high specific gravity
may be included as a filler. Specific examples of metals with a
high specific gravity include tungsten and molybdenum. The amount
of the filler is determined as appropriate so that the intended
specific gravity of the center 8 is accomplished. A particularly
preferable filler is zinc oxide. Zinc oxide serves not only as a
specific gravity adjuster but also as a crosslinking activator.
According to need, various additives such as sulfur, an anti-aging
agent, a coloring agent, a plasticizer, a dispersant, and the like
are included in the rubber composition of the center 8 in an
adequate amount. Crosslinked rubber powder or synthetic resin
powder may also be included in the center 8.
[0043] The center 8 preferably has a surface hardness H1 of equal
to or greater than 35 but equal to or less than 60. The center 8
having a surface hardness H1 of equal to or greater than 35 can
achieve excellent resilience performance. In this respect, the
surface hardness H1 is more preferably equal to or greater than 40
and particularly preferably equal to or greater than 45. The center
8 having a surface hardness H1 of equal to or less than 60 can
achieve excellent feel at impact. In this respect, the surface
hardness H1 is more preferably equal to or less than 55 and
particularly preferably equal to or less than 50. The surface
hardness H1 is measured by pressing a Shore D type hardness scale
against the surface of the center 8 from which the mid layer 10 and
the cover 6 have been removed. For the measurement, an automated
rubber hardness measurement machine (trade name "P1", manufactured
by Kobunshi Keiki Co., Ltd.), to which this hardness scale is
mounted, is used.
[0044] In light of feel at impact, the center 8 has an amount of
compressive deformation DF1 of preferably equal to or greater than
3.5 mm, more preferably equal to or greater than 4.0 mm, and
particularly preferably equal to or greater than 4.5 mm. In light
of resilience performance, the amount of compressive deformation
DF1 is preferably equal to or less than 6.5 mm, more preferably
equal to or less than 6.0 mm, and particularly preferably equal to
or less than 5.5 mm,
[0045] For measurement of the amount of compressive deformation, a
YAMADA type compression tester is used. In the tester, a sphere
(the center 8, the core 4, the golf ball 2, etc.) which is an
object to be measured is placed on a hard plate made of metal.
Next, a cylinder made of metal gradually descends toward the
sphere. The sphere, squeezed between the bottom face of the
cylinder and the hard plate, becomes deformed. A migration distance
of the cylinder, starting from the state in which an initial load
of 98 N is applied to the sphere up to the state in which a final
load of 1274 N is applied thereto, is measured. A moving speed of
the cylinder until the initial load is applied is 0.83 mm/s, A
moving speed of the cylinder after the initial speed is applied
until the final load is applied is 1.67 mm/s. The atmospheric
temperature at the measurement is 23.degree. C. Prior to the
measurement, the sphere is kept in a thermostat bath at 23.degree.
C. for 24 hours or longer.
[0046] The center 8 preferably has a diameter of equal to or
greater than 35.0 mm but equal to or less than 40.0 mm. The center
8 preferably has a weight of equal to or greater than 30 g but
equal to or less than 41 g. The temperature for crosslinking the
center 8 is equal to or higher than 140.degree. C. but equal to or
lower than 180.degree. C. The time period for crosslinking the
center 8 is equal to or longer than 10 minutes but equal to or
shorter than 60 minutes. The center 8 may include two or more
layers. The center 8 may have a rib on the surface thereof. The
center 8 may be hollow.
[0047] The mid layer 10 is formed from a thermoplastic resin
composition. Examples of the base polymer of the resin composition
include ionomer resins, thermoplastic polyester elastomers,
thermoplastic polyamide elastomers, thermoplastic polyurethane
elastomers, thermoplastic polyolefin elastomers, and thermoplastic
polystyrene elastomers. Ionomer resins are particularly preferred.
Ionomer resins are highly elastic. As described later, the cover 6
of the golf ball 2 is thin. When the golf ball 2 is hit, the mid
layer 10 significantly deforms due to the thinness of the cover 6.
Therefore, the mid layer 10 greatly influences resilience
performance. The golf ball 2 which includes the mid layer 10
including an ionomer resin has excellent resilience
performance.
[0048] An ionomer resin and another resin may be used in
combination. In this case, in light of resilience performance, the
ionomer resin is included as the principal component of the base
polymer. The proportion of the ionomer resin to the entire base
polymer is preferably equal to or greater than 50% by weight, more
preferably equal to or greater than 70% by weight, and particularly
preferably equal to or greater than 85% by weight.
[0049] Examples of preferable ionomer resins include binary
copolymers formed with an .alpha.-olefin and an
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon
atoms. A preferable binary copolymer includes 80% by weight or more
but 90% by weight or less of an .alpha.-olefin, and 10% by weight
or more but 20% by weight or less of an .alpha.,.beta.-unsaturated
carboxylic acid. The binary copolymer has excellent resilience
performance. Examples of other preferable ionomer resins include
ternary copolymers formed with: an .alpha.-olefin; an
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon
atoms; and an .alpha.,.beta.-unsaturated carboxylate ester having 2
to 22 carbon atoms. A preferable ternary copolymer includes 70% by
weight or more but 85% by weight or less of an .alpha.-olefin, 5%
by weight or more but 30% by weight or less of an
.alpha.,.beta.-unsaturated carboxylic acid, and 1% by weight or
more but 25% by weight or less of an .alpha.,.beta.-unsaturated
carboxylate ester. The ternary copolymer has excellent resilience
performance. For the binary copolymer and the ternary copolymer,
preferable .alpha.-olefins are ethylene and propylene, while
preferable .alpha.,.beta.-unsaturated carboxylic acids are acrylic
acid and methacrylic acid. A particularly preferable ionomer resin
is a copolymer formed with ethylene and acrylic acid. Another
particularly preferable ionomer resin is a copolymer formed with
ethylene and methacrylic acid.
[0050] 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. The neutralization may be carried out with
two or more types of metal ions. Particularly suitable metal ions
in light of resilience performance and durability of the golf ball
2 are sodium ion, zinc ion, lithium ion, and magnesium ion.
[0051] Specific examples of ionomer resins include trade names
"Himilan 1555", "Himilan 1557", "Himilan 1605", "Himilan 1706",
"Himilan 1707", "Himilan 1856", "Himilan 1855", "Himilan AM7311",
"Himilan AM7315", "Himilan AM7317", "Himilan AM7329", and "Himilan
AM7337", manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.;
trade names "Surlyn 6120", "Surlyn 6910", "Surlyn 7930", "Surlyn
7940", "Surlyn 8140", "Surlyn 8150", "Surlyn 8940", "Surlyn 8945",
"Surlyn 9120", "Surlyn 9150", "Surlyn 9910", "Surlyn 9945", "Surlyn
AD8546", "HPF1000", and "HPF2000", manufactured by E.I. du Pont de
Nemours and Company; and trade names "IOTEK 7010", "IOTEK 7030",
"IOTEK 7510", "IOTEK 7520", "IOTEK 8000", and "IOTEK 8030",
manufactured by ExxonMobil Chemical Corporation. Two or more
ionomer resins may be used in combination.
[0052] For the purpose of adjusting specific gravity and the like,
a filler may be included in the resin composition of the mid layer
10. Examples of suitable fillers include zinc oxide, barium
sulfate, calcium carbonate, and magnesium carbonate. Powder of a
metal with a high specific gravity may be included as a filler.
Specific examples of metals with a high specific gravity include
tungsten and molybdenum. The amount of the filler is determined as
appropriate so that the intended specific gravity of the mid layer
10 is accomplished. A coloring agent, crosslinked rubber powder, or
synthetic resin powder may also be included in the mid layer
10.
[0053] The mid layer 10 has a thickness of preferably equal to or
greater than 0.5 mm and more preferably equal to or greater than
1.0 mm. The thickness is preferably equal to or less than 2.0 mm
and more preferably equal to or less than 1.8 mm.
[0054] The mid layer 10 has a hardness H2 of preferably equal to or
greater than 55, more preferably equal to or greater than 60, and
particularly preferably equal to or greater than 63. The hardness
H2 is preferably equal to or less than 75, more preferably equal to
or less than 72, and particularly preferably equal to or less than
70.
[0055] In the present invention, the hardness H2 of the mid layer
10 and a hardness H3 of the cover 6 are measured according to the
standards of "ASTM-D 2240-68". For the measurement, an automated
rubber hardness measurement machine (trade name "P1", manufactured
by Kobunshi Keiki Co., Ltd.), to which a Shore D type hardness
scale is mounted, is used. For the measurement, a sheet that is
formed by hot press, is formed from the same material as that of
the mid layer 10 (or the cover 6), and has a thickness of about 2
mm is used. Prior to the measurement, a sheet is kept at 23.degree.
C. for two weeks. At the measurement, three sheets are stacked.
[0056] The core 4 (i.e., the center 8 and the mid layer 10)
preferably has a diameter of equal to or greater than 41.0 mm but
equal to or less than 42.0 mm. The core 4 preferably has a weight
of equal to or greater than 42.0 g but equal to or less than 44.0
g. The core 4 preferably has an amount of compressive deformation
DF2 of equal to or greater than 3.0 mm but equal to or less than
5.0 mm.
[0057] The cover 6 is formed from a resin composition. Examples of
the base resin of the resin composition include polyurethanes,
polyamide elastomers, styrene block-containing thermoplastic
elastomers, polyester elastomers, polyolefin elastomers, and
ionomer resins.
[0058] A preferable base polymer 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 thermoplastic polyurethane is flexible. The cover 6 in
which the polyurethane is used has excellent scuff resistance. When
a thermoplastic polyurethane and another resin are used in
combination for the cover 6, the proportion of the thermoplastic
polyurethane to the entire base resin is preferably equal to or
greater than 50% by weight, more preferably equal to or greater
than 60% by weight, and particularly preferably equal to or greater
than 70% by weight.
[0059] The thermoplastic polyurethane has a urethane bond within
the molecule. The urethane bond can be formed by reacting a polyol
with a polyisocyanate. The polyol, as a material for the urethane
bond, has a plurality of hydroxyl groups. Low-molecular-weight
polyols and high-molecular-weight polyols can be used.
[0060] Examples of low-molecular-weight polyols include diols,
triols, tetraols, and hexaols. Specific examples of diols include
ethylene glycol, diethylene glycol, triethylene glycol,
1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol,
dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol,
2,3-butanediol, 2,3-dimethyl-2,3-butanediol, neopentyl glycol,
pentanediol, hexanediol, heptanediol, octanediol, and
1,6-cyclohexanedimethylol. Aniline-based diols or bisphenol A-based
diols may be used. Specific examples of triols include glycerin,
trimethylol propane, and hexanetriol. Specific examples of tetraols
include pentaerythritol and sorbitol.
[0061] Examples of high-molecular-weight polyols include polyether
polyols such as polyoxyethylene glycol (PEG), polyoxypropylene
glycol (PPG), and polytetramethylene ether glycol (PTMG); condensed
polyester polyols such as polyethylene adipate (PEA), polybutylene
adipate (PBA), and polyhexamethylene adipate (PHMA); lactone
polyester polyols such as poly-.epsilon.-caprolactone (PCL);
polycarbonate polyols such as polyhexamethylene carbonate; and
acrylic polyols. Two or more polyols may be used in combination. In
light of feel at impact of the golf ball 2, the
high-molecular-weight polyol has a number average molecular weight
of preferably equal to or greater than 400 and more preferably
equal to or greater than 1000. The number average molecular weight
is preferably equal to or less than 10000.
[0062] Examples of polyisocyanates, as a material for the urethane
bond, include aromatic diisocyanates, alicyclic diisocyanates, and
aliphatic diisocyanates. Two or more types of diisocyanates may be
used in combination,
[0063] Examples of aromatic diisocyanates include 2,4-toluene
diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane
diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI),
3,3'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate
(XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene
diisocyanate (PPDI). One example of aliphatic diisocyanates is
hexamethylene diisocyanate (HDI). Examples of alicyclic
diisocyanates include 4,4'-dicyclohexylmethane diisocyanate
(H.sub.12MDI), 1,3-bis(isocyanatemethyl)cyclohexane (H.sub.6XDI)
isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane
diisocyanate (CHDI). 4,4'-dicyclohexylmethane diisocyanate is
preferable.
[0064] Specific examples of the thermoplastic polyurethane include
trade names "Elastollan XNY80A", "Elastollan XNY82A", "Elastollan
XNY85A", "Elastollan XNY90A", "Elastollan XNY97A", "Elastollan
XNY585", and "Elastollan XKP016N", manufactured by BASF Japan Ltd.;
and trade names "RESAMINE P4585LS" and "RESAMINE PS62490",
manufactured by Dainichiseika Color & Chemicals Mfg. Co.,
Ltd.
[0065] According to need, 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 are
included in the resin composition of the cover 6 in an adequate
amount.
[0066] The cover 6 preferably has a hardness H3 of equal to or
greater than 30 but equal to or less than 50. The golf ball 2
having a hardness H3 of equal to or greater than 30 has excellent
resilience performance. When the golf ball 2 is hit by an amateur
golf player, a long flight distance is achieved. In this respect,
the hardness H3 is more preferably equal to or greater than 31 and
particularly preferably equal to or greater than 32. The golf ball
2 having a hardness H3 of equal to or less than 50 has excellent
spin performance. The spin achieves a high trajectory of the golf
ball 2. When the golf ball 2 is hit by an amateur golf player,
excellent trajectory feeling is obtained. In this respect, the
hardness H3 is more preferably equal to or less than 45 and
particularly preferably equal to or less than 40.
[0067] The cover 6 preferably has a thickness of equal to or
greater than 0.3 mm but equal to or less than 1.8 mm. The golf ball
2 in which the thickness of the cover 6 is equal to or greater than
0.3 mm has excellent spin performance. The spin achieves a high
trajectory of the golf ball 2. When the golf ball 2 is hit by an
amateur golf player, excellent trajectory feeling is obtained. In
this respect, the thickness is more preferably equal to or greater
than 0.4 mm and particularly preferably equal to or greater than
0.5 mm. The golf ball 2 in which the thickness is equal to or less
than 1.8 mm has excellent resilience performance. When the golf
ball 2 is hit by an amateur golf player, a long flight distance is
achieved. Furthermore, the golf ball 2 in which the thickness of
the cover 6 is equal to or less than 1.8 mm is excellent in hit
feeling. In these respects, the thickness is more preferably equal
to or less than 1.0 mm and particularly preferably equal to or less
than 0.8 mm.
[0068] The golf ball 2 may include a reinforcing layer between the
mid layer 10 and the cover 6. The reinforcing layer firmly adheres
to the mid layer 10 and also to the cover 6. The reinforcing layer
suppresses separation of the mid layer 10 from the cover 6. The
reinforcing layer is formed from a resin composition. Examples of a
preferable base polymer of the reinforcing layer include
two-component curing type epoxy resins and two-component curing
type urethane resins.
[0069] The golf ball 2 has an amount of compressive deformation DF3
of equal to or greater than 3.0 mm but equal to or less than 5.0
mm. The golf ball 2 having an amount of compressive deformation DF3
of equal to or greater than 3.0 mm does not have excessive
resilience performance. The golf ball 2 can conform to the rules
about flight distance established by the USGA. Furthermore, with
the golf ball 2 having an amount of compressive deformation DF3 of
equal to or greater than 3.0 mm, soft hit feeling is obtained. In
these respects, the amount of compressive deformation DF3 is more
preferably equal to or greater than 3.5 mm and particularly
preferably equal to or greater than 3.8 mm. The golf ball 2 having
an amount of compressive deformation DF3 of equal to or less than
5.0 mm has excellent resilience performance. In this respect, the
amount of compressive deformation DF3 is more preferably equal to
or less than 4.7 mm and particularly preferably equal to or less
than 4.5 mm.
[0070] As shown in FIGS. 2 and 3, the contour of each dimple 12 is
circular. The golf ball 2 has dimples A each having a diameter of
4.6 mm; dimples B each having a diameter of 4.4 mm; dimples C each
having a diameter of 4.2 mm; dimples D each having a diameter of
4.0 mm; dimples E each having a diameter of 3.9 mm; and dimples F
each having a diameter of 2.6 mm. The number of types 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.
[0071] The number of the dimples A is 42; the number of the dimples
B is 72; the number of the dimples C is 66; the number of the
dimples D is 126; the number of the dimples E is 12; and the number
of the dimples F is 12. The total number of the dimples 12 is
330.
[0072] FIG. 4 shows a cross section along a plane passing through
the center of the dimple 12 and the center of the golf ball 2. In
FIG. 4, the top-to-bottom direction is the depth direction of the
dimple 12. In FIG. 4, a chain double-dashed line indicates a
phantom sphere 16. The surface of the phantom sphere 16 is the
surface of the golf ball 2 when it is postulated that no dimple 12
exists. The dimple 12 is recessed from the surface of the phantom
sphere 16. The land 14 coincides with the surface of the phantom
sphere 16. In the present embodiment, the cross-sectional shape of
each dimple 12 is substantially a circular arc.
[0073] In FIG. 4, a double ended arrow Dm indicates the diameter of
the dimple 12. The diameter Dm is the distance between two tangent
points Ed appearing on a tangent line Tg that is drawn tangent to
the far opposite ends of the dimple 12. Each tangent point Ed is
also the edge of the dimple 12. The edge Ed defines the contour of
the dimple 12. In FIG. 4, a double ended arrow Dp indicates the
depth of the dimple 12. The depth Dp is the distance between the
deepest part of the dimple 12 and the phantom sphere 16.
[0074] The diameter Dm of each dimple 12 is preferably equal to or
greater than 2.0 mm but equal to or less than 6.0 mm. The dimple 12
having a diameter Dm of equal to or greater than 2.0 mm contributes
to turbulization. In this respect, the diameter Dm is more
preferably equal to or greater than 2.5 mm and particularly
preferably equal to or greater than 2.8 mm. The dimple 12 having a
diameter Dm of equal to or less than 6.0 mm does not impair a
fundamental feature of the golf ball 2 that the golf ball 2 is
substantially a sphere. In this respect, the diameter Dm is more
preferably equal to or less than 5.5 mm and particularly preferably
equal to or less than 5.0 mm.
[0075] In light of suppression of rising of the golf ball 2 during
flight, the depth Dp of each dimple 12 is preferably equal to or
greater than 0.10 mm, more preferably equal to or greater than 0.13
mm, and particularly preferably equal to or greater than 0.15 mm.
In light of suppression of dropping of the golf ball 2 during
flight, the depth Dp is preferably equal to or less than 0.60 mm,
more preferably equal to or less than 0.55 mm, and particularly
preferably equal to or less than 0.50 mm.
[0076] The spherical surface area s of each dimple 12 is the area
of a zone surrounded by the contour line of the dimple 12, of the
surface of the phantom sphere 16 of the golf ball 2. In the golf
ball 2 shown in FIGS. 2 and 3, the spherical surface area s of each
dimple A is 16.61 mm.sup.2; the spherical surface area s of each
dimple B is 15.20 mm.sup.2; the spherical surface area s of each
dimple C is 13.85 mm.sup.2; the spherical surface area s of each
dimple D is 12.56 mm.sup.2; the spherical surface area s of each
dimple E is 11.94 mm.sup.2; and the spherical surface area s of
each dimple F is 5.31 mm.sup.2.
[0077] The ratio of the sum of the spherical surface areas s of all
the dimples 12 to the surface area of the phantom sphere 16 is
referred to as an occupation ratio. In light of turbulization, the
occupation ratio is preferably equal to or greater than 0.780, more
preferably equal to or greater than 0.800, and particularly
preferably equal to or greater than 0.840. The occupation ratio is
preferably equal to or less than 0.950. In the golf ball 2 shown in
FIGS. 2 and 3, the sum of the spherical surface areas s is 4495.3
mm.sup.2. The surface area of the phantom sphere 16 of the golf
ball 2 is 5728.0 mm.sup.2, and thus the occupation ratio is
0.785.
[0078] From the standpoint that a sufficient occupation ratio is
achieved, the total number of the dimples 12 is preferably equal to
or greater than 250, more preferably equal to or greater than 280,
and particularly preferably equal to or greater than 300. From the
standpoint that each dimple 12 can contribute to turbulization, the
total number of the dimples 12 is preferably equal to or less than
450, more preferably equal to or less than 400, and particularly
preferably equal to or less than 380.
[0079] In the present invention, the "volume of the dimple" means
the volume of a portion surrounded by the phantom sphere 16 and the
surface of the dimple 12. The total volume of the dimples 12 of the
golf ball 2 is preferably equal to or less than 580 mm.sup.3. With
the golf ball 2 in which the total volume is equal to or less than
580 mm.sup.3, a high trajectory is achieved. When the golf ball 2
is hit by an amateur golf player, excellent trajectory feeling is
obtained. In this respect, the total volume is more preferably
equal to or less than 560 mm.sup.3 and particularly preferably
equal to or less than 550 mm.sup.3. In light of suppression of
rising of the golf ball 2 during flight, the total volume is
preferably equal to or greater than 430 mm.sup.3.
[0080] The golf ball 2 meets the following mathematical formula
(I):
0.80.ltoreq.((L1+L2)/2).ltoreq.0.95 (I),
where: L1 represents the ratio (CL1/CD1) of a lift coefficient CL1
relative to a drag coefficient CD1, the lift coefficient CL1 and
the drag coefficient CD1 being measured under conditions of a
Reynolds number of 1.290.times.10.sup.5 and a spin rate of 2820
rpm; and L2 represents the ratio (CL2/CD2) of a lift coefficient
CL2 relative to a drag coefficient CD2, the lift coefficient CL2
and the drag coefficient CD2 being measured under conditions of a
Reynolds number of 1.771.times.10.sup.5 and a spin rate of 2940
rpm. The lift coefficients and the drag coefficients are measured
according to the Indoor Test Range (ITR) determined by the
USGA.
[0081] A Reynolds number is a dimensionless number used in the
field of fluid mechanics. A Reynolds number (Re) can be calculated
by the following mathematical formula:
Re=.rho.vL/.mu.,
where, .rho. represents the density of a fluid, v represents a
speed of an object, L represents a characteristic length, and .mu.
represents a viscosity coefficient of the fluid.
[0082] As described above, the Reynolds number at the measurements
of the lift coefficient CL1 and the drag coefficient CD1 is
1.290.times.10.sup.5. Regarding the golf ball 2 which flies in the
air, this Reynolds number corresponds to a ball speed when the golf
ball 2 is launched with a driver at a head speed of 35 m/s. The
spin rate at the measurements of the lift coefficient CL1 and the
drag coefficient CD1 is 2820 rpm. This spin rate is an average
value of a golf player having a head speed of 35 m/s. For
measurement of the ratio L1, a golf player having a head speed of
35 m/s is assumed.
[0083] As described above, the Reynolds number at the measurements
of the lift coefficient CL2 and the drag coefficient CD2 is
1.771.times.10.sup.5. Regarding the golf ball 2 which flies in the
air, this Reynolds number corresponds to a ball speed when the golf
ball 2 is launched with a driver at a head speed of 45 m/s. The
spin rate at the measurements of the lift coefficient CL2 and the
drag coefficient CD2 is 2940 rpm. This spin rate is an average
value of a golf player having a head speed of 45 m/s. For
measurement of the ratio L2, a golf player having a head speed of
45 m/s is assumed.
[0084] Many amateur golf players have a head speed of equal to or
greater than 35 m/s but equal to or less than 45 m/s. In the above
mathematical formula (I), the ratio L1 corresponding to a head
speed of 35 m/s and the ratio L2 corresponding to a head speed of
45 m/s are averaged. The golf ball 2 in which an average value
((L1+L2)/2) is equal to or greater than 0.80 but equal to or less
than 0.95 is suitable for many amateur golf players.
[0085] When the golf ball 2 in which the average value ((L1+L2)/2)
is equal to or greater than 0.80 is hit by an amateur golf player,
a high trajectory is achieved. Although the golf ball 2 conforms to
the rules of the USGA about flight distance, the golf player feels
satisfied with the trajectory. The golf ball 2 is excellent in
trajectory feeling. In this respect, the average value ((L1+L2)/2)
is more preferably equal to or greater than 0.84 and particularly
preferably equal to or greater than 0.88.
[0086] The golf ball 2 in which the average value ((L1+L2)/2) is
equal to or less than 0.95 is less likely to rise during flight. In
this respect, the average value ((L1+L2)/2) is more preferably
equal to or less than 0.93 and particularly preferably equal to or
less than 0.92.
[0087] The average value ((L1+L2)/2) can be achieved in the above
range by making the specifications of the dimples 12 appropriate.
Specifically, the ratio L1 and the ratio L2 can be made appropriate
to achieve the average value ((L1+L2)/2) in the above range, by
means such as:
[0088] (1) making the depth of each dimple 12 appropriate;
[0089] (2) making the area of each dimple 12 appropriate;
[0090] (3) making the volume of each dimple 12 appropriate;
[0091] (4) making the number of the dimples 12 appropriate;
[0092] (5) making the occupation ratio of the dimples 12
appropriate; and the like.
[0093] The ratio L1 is preferably equal to or greater than 0.85 but
equal to or less than 0.93. When the golf ball 2 having a ratio L1
of equal to or greater than 0.85 is hit with a driver at a head
speed of 35 m/s, a high trajectory is achieved. Although the golf
ball 2 conforms to the rules of the USGA about flight distance, the
golf player feels satisfied with the trajectory. The golf ball 2 is
excellent in trajectory feeling. In this respect, the ratio L1 is
more preferably equal to or greater than 0.87 and particularly
preferably equal to or greater than 0.88. The golf ball 2 having a
ratio L1 of equal to or less than 0.93 is less likely to rise
during flight. In this respect, the ratio L1 is particularly
preferably equal to or less than 0.92.
[0094] The ratio L2 is preferably equal to or greater than 0.76 but
equal to or less than 0.92. When the golf ball 2 having a ratio L2
of equal to or greater than 0.76 is hit with a driver at a head
speed of 45 m/s, a high trajectory is achieved. Although the golf
ball 2 conforms to the rules of the USGA about flight distance, the
golf player feels satisfied with the trajectory. The golf ball 2 is
excellent in trajectory feeling. In this respect, the ratio L2 is
more preferably equal to or greater than 0.80 and particularly
preferably equal to or greater than 0.86. The golf ball 2 having a
ratio L2 of equal to or less than 0.92 is less likely to rise
during flight. In this respect, the ratio L2 is particularly
preferably equal to or less than 0.91.
EXAMPLES
Example 1
[0095] A rubber composition was obtained by kneading 100 parts by
weight of a high-cis polybutadiene (trade name "BR-730",
manufactured by JSR Corporation), 22.5 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, and
0.6 parts by weight of dicumyl peroxide. This rubber composition
was placed into a mold including upper and lower mold halves each
having a hemispherical cavity, and heated at 170.degree. C. for 18
minutes to obtain a center with a diameter of 38.5 mm.
[0096] 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 ("Himilan AM7329", manufactured by Du
Pont-MITSUI POLYCHEMICALS Co., Ltd.), and 4 parts by weight of
titanium dioxide with a twin-screw kneading extruder. The center
was covered with the resin composition by injection molding to form
a mid layer with a thickness of 1.6 mm.
[0097] 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.degree. C. for 6 hours
to obtain a reinforcing layer with a thickness of 10 .mu.m.
[0098] 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 formed from this resin composition by compression
molding. The sphere consisting of the center, the mid layer, and
the reinforcing layer was covered with two of these half shells.
The 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 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. 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 dimple specifications D3 shown in Table 1 below.
Examples 2 to 11 and Comparative Examples 1 to 9
[0099] Golf balls of Examples 2 to 11 and Comparative Examples 1 to
9 were obtained in the same manner as Example 1, except the
specifications of the center, the mid layer, the cover, and the
dimples were as shown in Tables 5 to 8 below. The composition of
the center is shown in detail in Table 1 below. The compositions of
the mid layer and the cover are shown in detail in Table 2 below.
The specifications of the dimples are shown in detail in Tables 3
and 4 below.
[0100] [Flight Test]
[0101] A driver with a head made of a titanium alloy (trade name
"XXIO", manufactured by DUNLOP SPORTS CO. LTD., shaft hardness: R,
loft angle: 11.degree.) was attached to a swing machine
manufactured by Golf Laboratories, Inc. A golf ball was hit under a
condition of a head speed of 40 m/sec, and a ball speed, a launch
angle, a spin rate, highest point coordinates (x,y), and a carry
were measured. The coordinate x is the horizontal distance from the
launch point to the highest point. The coordinate y is the vertical
distance from the launch point to the highest point. The carry is
the distance from the launch point to the landing point. The
results are shown in Tables 9 to 12 below.
[0102] [Sensuous Evaluation]
[0103] Ten testers hit golf balls with drivers and evaluated
trajectory feeling and hit feeling. The evaluation was categorized
on the basis of the following criteria. The results are shown in
Tables 9 to 12 below.
[0104] Trajectory feeling: the number of testers who feel that a
flight distance is long. [0105] A: 8 or more [0106] B: 5 to 7
[0107] C: 2 to 4 [0108] D: 1 or less
[0109] Hit feeling: the number of tester who feel soft. [0110] A: 8
or more [0111] B: 5 to 7 [0112] C: 2 to 4 [0113] D: 1 or less
TABLE-US-00001 [0113] TABLE 1 Composition of Center (parts by
weight) T1 T2 T3 T4 T5 BR730 100 100 100 100 100 Zinc 18.5 20.0
22.5 26.5 27.5 diacrylate Zinc oxide 5 5 5 5 5 Barium * * * * *
sulfate Diphenyl 0.5 0.5 0.5 0.5 0.5 disulfide Dicumyl 0.5 0.5 0.6
0.7 0.7 peroxide *: Appropriate amount
TABLE-US-00002 TABLE 2 Compositions of Mid Layer and Cover (parts
by weight) M1 C1 C2 C3 C4 C5 Himilan 50 #1605 Himilan 50 50 AM7329
Himilan 24 AM7337 Rabalon 26 T3221C Barium 17 sulfate Elastollan
100 XNY82A Elastollan 100 XNY85A Elastollan 100 XNY90A Elastollan
100 XNY97A Titanium 4 4 4 4 4 6 dioxide Hardness 65 29 32 38 47 52
(Shore D)
TABLE-US-00003 TABLE 3 Specifications of Dimples Number of Diameter
Depth Volume Type dimples (mm) (mm) (mm.sup.3) D1 A 42 4.6 0.224
1.865 B 72 4.4 0.214 1.626 C 66 4.2 0.183 1.272 D 126 4.0 0.164
1.030 E 12 3.9 0.149 0.892 F 12 2.6 0.100 0.265 D2 A 42 4.6 0.244
2.032 B 72 4.4 0.234 1.778 C 66 4.2 0.203 1.411 D 126 4.0 0.184
1.156 E 12 3.9 0.169 1.011 F 12 2.6 0.120 0.318 D3 A 42 4.6 0.264
2.198 B 72 4.4 0.254 1.931 C 66 4.2 0.223 1.550 D 126 4.0 0.204
1.282 E 12 3.9 0.189 1.131 F 12 2.6 0.140 0.371 D4 A 42 4.6 0.274
2.282 B 72 4.4 0.264 2.007 C 66 4.2 0.233 1.619 D 126 4.0 0.214
1.345 E 12 3.9 0.199 1.191 F 12 2.6 0.150 0.398
TABLE-US-00004 TABLE 4 Specifications of Dimples Number of Diameter
Depth Volume Type dimples (mm) (mm) (mm.sup.3) D5 A 42 4.6 0.284
2.365 B 72 4.4 0.274 2.083 C 66 4.2 0.243 1.689 D 126 4.0 0.224
1.408 E 12 3.9 0.209 1.251 F 12 2.6 0.160 0.425 D6 A 42 4.6 0.294
2.449 B 72 4.4 0.284 2.160 C 66 4.2 0.253 1.759 D 126 4.0 0.234
1.471 E 12 3.9 0.219 1.311 F 12 2.6 0.170 0.451 D7 A 42 4.6 0.334
2.783 B 72 4.4 0.324 2.466 C 66 4.2 0.293 2.038 D 126 4.0 0.274
1.724 E 12 3.9 0.259 1.551 F 12 2.6 0.210 0.559
TABLE-US-00005 TABLE 5 Specifications of Golf Ball Comp. Ex. 3 Ex.
1 Ex. 2 Ex. 3 Ex. 4 Center Composition T3 T3 T3 T3 T3 Diameter
38.50 38.50 38.50 38.50 38.50 H1 (D) 46 46 46 46 46 DF1 (mm) 5.05
5.05 5.05 5.05 5.05 Weight (g) 35.0 35.0 35.0 35.0 35.0 Mid
Composition M1 M1 M1 M1 M1 layer Thickness 1.60 1.60 1.60 1.60 1.60
(mm) H2 (D) 65 65 65 65 65 Diameter 41.70 41.70 41.70 41.70 41.70
Core DF2 (mm) 4.30 4.30 4.30 4.30 4.30 Weight (g) 43.4 43.4 43.4
43.4 43.4 Cover Composition C2 C2 C2 C2 C2 Thickness 0.50 0.50 0.50
0.50 0.50 (mm) H3 (D) 32 32 32 32 32 Ball Diameter 42.70 42.70
42.70 42.70 42.70 DF3 (mm) 4.10 4.10 4.10 4.10 4.10 Weight (g) 45.6
45.6 45.6 45.6 45.6 Dimple Specifications D1 D2 D3 D4 D5 Total
volume 423 468 513 536 558 (mm.sup.3) CD1 0.311 0.287 0.274 0.238
0.233 CL1 0.301 0.266 0.252 0.211 0.198 L1 0.968 0.928 0.918 0.887
0.852 CD2 0.255 0.243 0.229 0.225 0.224 CL2 0.241 0.221 0.196 0.180
0.171 L2 0.945 0.912 0.860 0.801 0.761 (L1 + L2)/2 0.956 0.920
0.889 0.844 0.806
TABLE-US-00006 TABLE 6 Specifications of Golf Ball Comp. Comp.
Comp. Ex. 4 Ex. 5 Ex. 6 Ex. 5 Ex. 6 Center Composition T3 T3 T1 T2
T4 Diameter 38.50 38.50 38.50 38.50 38.50 H1 (D) 46 46 38 42 51 DF1
(mm) 5.05 5.05 6.05 5.75 4.05 Weight (g) 35.0 35.0 35.0 35.0 35.0
Mid Composition M1 M1 M1 M1 M1 layer Thickness 1.60 1.60 1.60 1.60
1.60 (mm) H2 (D) 65 65 65 65 65 Diameter 41.70 41.70 41.70 41.70
41.70 Core DF2 (mm) 4.30 4.30 5.30 5.00 3.30 Weight (g) 43.4 43.4
43.4 43.4 43.4 Cover Composition C2 C2 C2 C2 C2 Thickness 0.50 0.50
0.50 0.50 0.50 (mm) H3 (D) 32 32 32 32 32 Ball Diameter 42.70 42.70
42.70 42.70 42.70 DF3 (mm) 4.10 4.10 5.10 4.80 3.10 Weight (g) 45.6
45.6 45.6 45.6 45.6 Dimple Specifications D6 D7 D3 D3 D3 Total
volume 581 672 513 513 513 (mm.sup.3) CD1 0.235 0.238 0.274 0.274
0.274 CL1 0.197 0.169 0.252 0.252 0.252 L1 0.839 0.709 0.918 0.918
0.918 CD2 0.228 0.235 0.229 0.229 0.229 CL2 0.170 0.155 0.196 0.196
0.196 L2 0.745 0.661 0.860 0.860 0.860 (L1 + L2)/2 0.792 0.685
0.889 0.889 0.889
TABLE-US-00007 TABLE 7 Specifications of Golf Ball Comp. Comp.
Comp. Ex. 7 Ex. 8 Ex. 7 Ex. 8 Ex. 9 Center Composition T5 T3 T3 T3
T3 Diameter 38.50 38.50 38.50 38.50 38.50 H1 (D) 54 46 46 46 46 DF1
(mm) 3.85 5.05 5.05 5.05 5.05 Weight (g) 35.0 35.0 35.0 35.0 35.0
Mid Composition M1 M1 M1 M1 M1 layer Thickness 1.60 1.60 1.60 1.60
1.60 (mm) H2 (D) 65 65 65 65 65 Diameter 41.70 41.70 41.70 41.70
41.70 Core DF2 (mm) 3.10 4.30 4.30 4.30 4.30 Weight (g) 43.4 43.4
43.4 43.4 43.4 Cover Composition C2 C1 C3 C4 C5 Thickness 0.50 0.50
0.50 0.50 0.50 (mm) H3 (D) 32 29 38 47 53 Ball Diameter 42.70 42.70
42.70 42.70 42.70 DF3 (mm) 2.85 4.15 4.05 4.00 3.95 Weight (g) 45.6
45.6 45.6 45.6 45.6 Dimple Specifications D3 D3 D3 D3 D3 Total
volume 513 513 513 513 513 (mm.sup.3) CD1 0.274 0.274 0.274 0.274
0.274 CL1 0.252 0.252 0.252 0.252 0.252 L1 0.918 0.918 0.918 0.918
0.918 CD2 0.229 0.229 0.229 0.229 0.229 CL2 0.196 0.196 0.196 0.196
0.196 L2 0.860 0.860 0.860 0.860 0.860 (L1 + L2)/2 0.889 0.889
0.889 0.889 0.889
TABLE-US-00008 TABLE 8 Specifications of Golf Ball Comp. Comp. Ex.
9 Ex. 10 Ex. 11 Ex. 1 Ex. 2 Center Composition T3 T3 T3 T4 T4
Diameter 37.50 36.50 35.50 38.50 38.50 H1 (D) 46 46 46 51 51 DF1
(mm) 5.05 5.05 5.05 4.05 4.05 Weight (g) 32.3 29.8 27.4 35.0 35.0
Mid Composition M1 M1 M1 M1 M1 layer Thickness 1.60 1.60 1.60 1.60
1.60 (mm) H2 (D) 65 65 65 65 65 Diameter 40.70 39.70 38.70 41.70
41.70 Core DF2 (mm) 4.30 4.30 4.30 3.30 3.30 Weight (g) 40.3 37.4
34.6 43.4 43.4 Cover Composition C4 C4 C4 C3 C3 Thickness 1.00 1.50
2.00 0.50 0.50 (mm) H3 (D) 47 47 47 38 38 Ball Diameter 42.70 42.70
42.70 42.70 42.70 DF3 (mm) 4.05 4.10 4.15 3.05 3.05 Weight (g) 45.6
45.6 45.6 45.6 45.6 Dimple Specifications D3 D3 D3 D6 D7 Total
volume 513 513 513 581 672 (mm.sup.3) CD1 0.274 0.274 0.274 0.235
0.238 CL1 0.252 0.252 0.252 0.197 0.169 L1 0.918 0.918 0.918 0.839
0.709 CD2 0.229 0.229 0.229 0.228 0.235 CL2 0.196 0.196 0.196 0.170
0.155 L2 0.860 0.860 0.860 0.745 0.661 (L1 + L2)/2 0.889 0.889
0.889 0.792 0.685
TABLE-US-00009 TABLE 9 Results of Evaluation Comp. Ex. Ex. Ex. Ex.
Ex. 3 1 2 3 4 Cover thickness 0.50 0.50 0.50 0.50 0.50 (mm)
Hardness H3 32 32 32 32 32 (D) Deformation 4.10 4.10 4.10 4.10 4.10
DF3 (mm) Total volume 423 468 513 536 558 (mm.sup.3) L1 0.968 0.928
0.918 0.887 0.852 L2 0.945 0.912 0.860 0.801 0.761 (L1 + L2)/2
16.473 16.456 16.430 16.400 16.381 Flight test Ball speed 56.80
56.80 56.80 56.80 56.80 (m/s) Launch angle 12.5 12.5 12.5 12.5 12.5
(deg) Spin (rpm) 2850 2850 2850 2850 2850 Highest point 102 107 111
109 111 (x) Highest point 24 23 22 21 19 (y) Carry (m) 162 166 168
176 177 Feeling Trajectory C B A A B feeling Hit feeling A A A A
A
TABLE-US-00010 TABLE 10 Results of Evaluation Comp. Comp. Comp. Ex.
Ex. Ex. Ex. Ex. 4 5 6 5 6 Cover thickness 0.50 0.50 0.50 0.50 0.50
(mm) Hardness H3 32 32 32 32 32 (D) Deformation 4.10 4.10 5.10 4.80
3.10 DF3 (mm) Total volume 581 672 513 513 513 (mm.sup.3) L1 0.839
0.709 0.918 0.918 0.918 L2 0.745 0.661 0.860 0.860 0.860 (L1 +
L2)/2 16.372 16.330 16.430 16.430 16.430 Flight test Ball speed
56.80 56.80 55.70 56.30 57.45 (m/s) Launch angle 12.5 12.5 12.8
12.7 12.4 (deg) Spin (rpm) 2850 2850 2700 2750 2900 Highest point
113 107 107 107 111 (x) Highest point 18 17 21 22 23 (y) Carry (m)
179 173 164 166 170 Feeling Trajectory C D A A A feeling Hit
feeling A A C B B
TABLE-US-00011 TABLE 11 Results of Evaluation Comp. Comp. Comp. Ex.
Ex. Ex. Ex. Ex. 7 8 7 8 9 Cover thickness 0.50 0.50 0.50 0.50 0.50
(mm) Hardness H3 32 29 38 47 53 (D) Deformation 2.85 4.15 4.05 4.00
3.95 DF3 (mm) Total volume 513 513 513 513 513 (mm.sup.3) L1 0.918
0.918 0.918 0.918 0.918 L2 0.860 0.860 0.860 0.860 0.860 (L1 +
L2)/2 16.430 14.930 19.430 23.930 26.930 Flight test Ball speed
57.55 56.75 56.85 56.90 56.95 (m/s) Launch angle 12.3 12.3 13.1
13.4 13.5 (deg) Spin (rpm) 2950 2950 2550 2400 2350 Highest point
111 108 109 112 114 (x) Highest point 23 22 22 22 22 (y) Carry (m)
170 165 171 175 178 Feeling Trajectory A C A A A feeling Hit
feeling D A A A A
TABLE-US-00012 TABLE 12 Results of Evaluation Comp. Comp. Ex. Ex.
Ex. Ex. Ex. 9 10 11 1 2 Cover thickness 1.00 1.50 2.00 0.50 0.50
(mm) Hardness H3 47 47 47 38 38 (D) Deformation 4.05 4.10 4.15 3.05
3.05 DF3 (mm) Total volume 513 513 513 581 672 (mm.sup.3) L1 0.918
0.918 0.918 0.839 0.709 L2 0.860 0.860 0.860 0.745 0.661 (L1 +
L2)/2 23.930 23.930 23.930 19.372 19.330 Flight test Ball speed
56.85 56.80 56.75 57.50 57.50 (m/s) Launch angle 13.0 12.8 12.7
13.0 13.0 (deg) Spin (rpm) 2600 2700 2750 2600 2600 Highest point
111 110 108 115 108 (x) Highest point 22 22 22 19 18 (y) Carry (m)
169 168 166 183 176 Feeling Trajectory A A B A D feeling Hit
feeling A A B C C
[0114] As shown in Tables 9 to 12, the golf ball of each Example is
excellent in various performance characteristics. From the results
of evaluation, advantages of the present invention are clear.
[0115] The golf ball according to the present invention is suitable
for, for example, playing golf on golf courses and practicing at
driving ranges. The above descriptions are merely illustrative
examples, and various modifications can be made without departing
from the principles of the present invention.
* * * * *